Key Words Flashcards

Question

COLLAGEN

Answer 1

A fibrous structural protein, consisting of three polypeptide chains twisted around each other. Almost every third amino acid in each polypeptide is glycine. Its small size allows the three strands to lie close together. Strength is provided by many hydrogen bonds and covalent bonds between the chains. The chains form a collagen fibril that links with other fibrils to form a collagen fibre. Provides strength in artery walls, tendons, cartilage and bone plus elasticity of the skin.

Answer 2

This occurs when an inhibitor molecule with the same shape as the normal substrate, binds to the active site of an enzyme, blocking access to the substrate. This type of inhibition is reversed by increasing the concentration of the substrate.

Answer 3

In a DNA molecule, a purine base pairs with a pyrimidine base. Guanine forms three hydrogen bonds with cytosine; adenine forms two hydrogen bonds with thymine.

Answer 4

Two molecules are joined together with a covalent bond. A larger molecule is formed and one molecule of water is released.

Answer 5

A globular protein with a prosthetic group such as haem in haemoglobin; cytochromes; phytochromes; lipoproteins.

Answer 6

A strong bond formed when pairs of electrons are shared between non-metal atoms and in compounds formed between non-metals. E.g. glucose C6H12O6

Answer 7

A change in the tertiary structure of proteins such as enzymes. At high temperatures, hydrogen and ionic bonds which help stabilise the tertiary structure break and the shape of the active site is disrupted. The enzyme can no longer form enzyme-substrate complexes. Thermal denaturation is usually irreversible; denaturation by changes in pH is often reversible.

Answer 8

A molecule formed by two monosaccharides that join together using a covalent bond called a glycosidic bond. Each glycosidic bond is formed during a condensation reaction with the loss of two hydrogen atoms and one oxygen atom. e.g. sucrose; maltose; lactose.

Answer 9

A covalent bond formed between sulfur atoms of the R groups of two cysteine or methionine or taurine amino acids

Answer 10

Deoxyribose nucleic acid is a double stranded polymer of nucleotide molecules that carries the information for protein synthesis. Contains the pentose sugar deoxyribose and the bases, adenine, thymine; cytosine and guanine.

Answer 11

An enzyme that breaks the hydrogen bonds between complementary base pairs of DNA. This causes the double strand of DNA to separate into single strands.

Answer 12

An enzyme that links free individual DNA nucleotides together by forming phosphodiester bonds. These bonds form between the 3' hydroxyl group of the end nucleotide to the 5' phosphate of the nucleotide to be added.

Answer 13

Chemical test for the presence of lipids. Ethanol is added to the lipid sample to dissolve the lipid. The lipid ethanol sample is then added to water to produce a milky/ cloudy suspension.

Answer 14

A globular protein molecule made by cells that acts as a catalyst and increases the rate of a specific chemical reaction

Answer 15

The complex that forms in the active site after the reaction is complete but before the product or products leave the active site.

Answer 16

The complex which forms when a substrate molecule fits into the active site of an enzyme

Answer 17

A covalent bond formed during a condensation reaction between the -OH group of glycerol and the -COOH group of a fatty acid.

Answer 18

A molecule with a hydrocarbon chain of varying length, attached to a carboxylic acid [-COOH]

Answer 19

A protein whose molecules have a relatively long, thin structure that are generally insoluble in water and metabolically inactive. Fibrous proteins such as keratin in hair and nails and collagen in skin, bone and cartilage have structural roles. The blood clotting protein, fibrin is also a fibrous protein.

Answer 20

A protein whose molecules fold into a three dimensional spherical shape. They are often water soluble and metabolically active e.g. enzymes; insulin; antibodies; plasma proteins and components of the cytoskeleton.

Answer 21

A three carbon alcohol molecule that forms ester bonds with three fatty acids to form a triglyceride.

Answer 22

A branched, insoluble polymer of alpha glucose monomers, linked together by 1,4 and 1,6 glycosidic bonds. Stored as small granules in muscle and liver cells; also found in hyphae of fungi.

Answer 23

A covalent bond formed when two carbohydrate molecules are joined together by a condensation reaction

Answer 24

A haemoglobin molecule consists of two alpha and two beta polypeptide chains. Each chain is associated with an iron containing haem prosthetic group. Each of the four haem groups can bind to a molecule of oxygen to form oxyhaemoglobin.

Answer 25

A weak electrostatic bond between two polarised molecules, both of which have an uneven distribution of electron charge.

Answer 26

The covalent bond between two molecules is broken with the addition of a water molecule, which separates the two molecules

Answer 27

The association between hydrophobic ['water hating'] R groups of amino acids [e.g. CH3 on alanine] where water is excluded. These hydrophobic interactions help to maintain the tertiary structure of a protein.

Answer 28

The shape of the enzyme's active site is moulded around the substrate so that the two fit closely together.

Answer 29

Iodine dissolved in potassium iodide solution. A yellow-brown solution. Reagent is used to test for the presence of starch. Amylose in starch forms a deep blue complex in the presence of iodine solution. Since amylopectin is highly branched, it binds only a small amount of iodine and produces a paler purple-red colour.

Answer 30

A charged atom or molecule which has lost or gained electrons. In a positively charged ion, the number of electrons is fewer than the number of protons. In a negatively charged ion, the number of electrons is greater than the number of protons.

Answer 31

A strong bond resulting from an electrostatic attraction between oppositely charged ions. E.g. Na+ and Cl- forming NaCl.

Answer 32

Molecule containing the same number and types of atoms but the atoms are arranged differently. Examples are α and β glucose.

Answer 33

The energy required to evaporate 1kg of water at its boiling point. Water has a high latent heat of vaporisation due to hydrogen bonding between water molecules. Evaporation of water such as sweat is an effective means of cooling.

Answer 34

The idea that the enzyme's active site is complementary in shape to the substrate in the same way as a key [substrate] and a lock [enzyme]

Answer 35

Bundles of beta glucose chains [in cellulose] held together by hydrogen bonds, which form cross links between adjacent beta glucose chains.

Answer 36

A single smaller molecule that forms the basic unit of polymers. Monomers form covalent bonds with other similar monomers as a result of condensation reactions. The monomers of the following groups are: carbohydrates - hexose sugars; lipids - fatty acids and glycerol; proteins - amino acids; nucleic acids - nucleotides.

Answer 37

A simple small sugar molecule which is sweet tasting and soluble. General formula (CH2O)n where n can be any number from three to seven. e.g. hexoses such as glucose; fructose; pentoses such as ribose; trioses such as glyceraldehyde

Answer 38

This occurs when an inhibitor molecule combines with an allosteric site on an enzyme. The tertiary structure of the protein changes, making the active site unable to bind to the normal substrate. This type of inhibition is not reversed by increasing the substrate concentration.

Answer 39

A sugar that cannot donate electrons from the carbonyl group [C=O] to Cu2+ ions in Benedict’s reagent, so that an insoluble red precipitate of copper (I) oxide is formed. Many disaccharides are non-reducing sugars e.g. sucrose. To detect a non-reducing sugar, the disaccharide must first be hydrolysed into its monosaccharide components by gently boiling with hydrochloric acid.

Answer 40

Inhibition that occurs when an inhibitor forms covalent bonds as it combines permanently with an enzyme and completely inactivates it.

Answer 41

A monomer of nucleic acids such as RNA and DNA. Each nucleotide consists of three components: a pentose [5 carbon] sugar; phosphate group and a nitrogen containing organic base [cytosine C; thymine T; uracil U; guanine G; adenine A.]

Answer 42

The temperature at which the rate of an enzyme controlled chemical reaction is at its maximum. Above or below this temperature, the rate is slower. The optimum temperature for an enzyme varies according to the habitat to which an organism is adapted.

Answer 43

A nitrogen-containing organic compound that is a constituent of nucleotides. The five organic bases are Adenine; Thymine; Cytosine, Guanine and Uracil.

Answer 44

The bond which forms when two amino acids are joined together by a condensation reaction with the loss of a water molecule [The -OH from the -COOH group of one amino acid combines with a -H from the amino group from the second amino acid].

Answer 45

In the DNA and RNA backbone, this is a covalent linkage formed during a condensation reaction . The phosphodiester bond links a phosphate group to a 3' carbon and a 5' carbon in two sugar molecules.

Answer 46

A molecule of glycerol combined with two fatty acids by ester bonds formed during condensation reactions. The third -OH group on glycerol is occupied by a phosphate group. A bilayer of phospholipids forms the basic structure of cell membranes.

Answer 47

Specialised membrane bound organelles found in plant cells e.g. chloroplasts and amyloplasts. Amyloplasts store starch grains.

Answer 48

A molecule with an uneven distribution of electrons and hence negative charge. Within a polar molecule there will be regions of delta positive and delta negative charge e.g. water molecule

Answer 49

A large molecule composed of many monomer units joined together by covalent bonds during condensation reactions e.g. proteins; starch; lipids; nucleic acids.

Answer 50

A chain of nucleotide monomers covalently linked together.

Answer 51

A long chain of amino acids joined together by repeated covalent peptide bonds

Answer 52

Large insoluble polymers formed from many monosaccharides that combine by condensation reactions to create long chains. e.g. starch [amylose and amylopectin] ; cellulose; glycogen; chitin.

Answer 53

The type, number and sequence of amino acids in an amino acid chain, held together by peptide bonds.

Answer 54

A non-protein part of a protein molecule that is permanently attached to the molecule and is vital for the normal functioning of the molecule e.g. haem.

Answer 55

A group of nitrogen bases which form part of a nucleotide. Purines are double ringed carbon-nitrogen compounds e.g. adenine and guanine

Answer 56

A group of nitrogen bases which form part of a nucleotide. Pyrimidines are single ringed carbon-nitrogen compounds e.g. cytosine; thymine in DNA and cytosine and uracil in RNA.

Answer 57

Non numerical, descriptive data which can be observed and recorded. e.g. gender; hair colour; language spoken

Answer 58

Numerical data which can be observed and measured. e.g. body mass; volume; time;

Answer 59

The three dimensional arrangement of two or more polypeptide chains or of a polypeptide and a prosthetic group [non protein component] such as haem, in a protein molecule.

Answer 60

Called a residual group. Consists of a variety of different chemical groups. Each amino acid has a different R group. The 20 naturally occurring amino acids differ only in their R group e.g. glycine has a single hydrogen atom as its R group; alanine has a CH3 R group.

Answer 61

A sugar that can donate electrons from the carbonyl group [C=O] to Cu2+ ions in Benedict’s reagent so that an insoluble red precipitate of copper (I) oxide is formed. All monosaccharides are reducing sugar and some disaccharides e.g. maltose; lactose

Answer 62

Inhibition that occurs when an inhibitor molecule temporarily combines with an enzyme. The inhibition is reversed and the enzyme becomes active again, once the inhibitor is no longer attached to the enzyme. Reversible inhibitors can be competitive or non-competitive.

Answer 63

Ribose nucleic acid is a single stranded polymer of nucleotide molecules containing the pentose sugar ribose and the base uracil instead of thymine. There are three types of RNA [rRNA; mRNA, tRNA] which all have important roles in protein synthesis.

Answer 64

A fatty acid with a long hydrocarbon chain where only single bonds occurs between adjacent carbon atoms

Answer 65

Each new DNA molecule is formed from one parental strand of the original DNA molecule which acts as the template and one strand of new DNA nucleotides

Answer 66

Dissolved solids, liquids or gases in a liquid [solvent] which can form a solution.

Answer 67

A liquid [the solvent] with dissolved solids, liquids or gases [solutes].

Answer 68

The energy required to raise the temperature of 1kg of water by 1C. Water has a high specific heat capacity due to the large number of hydrogen bonds between water molecules. Water acts a buffer against sudden temperature changes.

Answer 69

The relationship between an enzyme and the type of substrate molecule with a particular shape that fits into the active site of the enzyme

Answer 70

Where water molecules meet air, hydrogen bonds tend to pull water molecules back into the body of the water rather than the molecules escaping into the air. The water surface acts like a skin and is often strong enough to support small invertebrates such as pond skaters

Answer 71

The structure of a protein molecule resulting from the three dimensional coiling or twisting of the already folded chain of amino acids. The two main types of tertiary structure are globular and fibrous. The tertiary structure is maintained by disulphide bridges; ionic bonds; hydrogen bonds and hydrophobic interactions between different R groups.

Answer 72

A lipid whose molecules are made up of a glycerol molecule combined to three fatty acids.

Answer 73

A fatty acid with a long hydrocarbon chain where there are some double bonds between adjacent carbon atoms

Answer 74

The movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

Answer 75

The centromeres divide and the newly separated chromatids are pulled by their centromeres to opposite poles of the cell. The spindle fibres shorten at both ends so pulling the chromatids apart.

Answer 76

A plasma protein known as an immunoglobulin. Synthesised by B cells. Y shaped molecule consisting of four polypeptide chains [two long heavy chains; two short light chains] with two specific identical binding sites in the variable region. Each binding site fits precisely onto a specific antigen.

Answer 77

Any part of an organism or substance that is recognised as foreign/non-self by the immune system and stimulates an immune response. Antigens are often proteins on the cell surface membranes or cell walls of invading cells such as microorganisms or abnormal body cells.

Answer 78

Macrophages in the lymph nodes engulf pathogens by endocytosis and then 'cut up'. Antigens from the bacterial or virus surface are incorporated within proteins which then become part of the macrophage cell surface membrane.

Answer 79

This occurs when pathogens mutate frequently and their antigens change suddenly. Existing vaccines become ineffective

Answer 80

This forms the basis of vaccination [immunisation]. The vaccine contains one or more antigens to stimulate an immune response

Answer 81

Occurs when antibodies are introduced into individuals from another source. No direct contact with the antigen is required to produce immunity. Antibodies are not replaced when they are broken down and no memory cells are formed so there is no lasting immunity. Examples include anti- venom given to victims of snake bites. People who are likely to have tetanus, diphtheria or rabies are often given antitoxin antibodies by injection as a precaution

Answer 82

A type of reproduction that does not involve the fusion of sex cells/gametes or a change in the number of chromosomes. Offspring are produced from a single individual and are genetically identical to the parent organism. E.g. vegetative propagation; parthenogenesis; budding; spore formation, fragmentation.

Answer 83

Originate from stem cells in the bone marrow, where they differentiate and mature. B cells spread out through the body's lymphatic system and during an immune response, they become plasma cells

Answer 84

A form of asexual reproduction in bacteria and some single celled eukaryotes such as Amoeba and Paramecium. During binary fission, the fully grown parent cell divides into two and each half becomes an independent organism.

Answer 85

To determine, rectify or mark the graduations of a measuring instrument. e.g. using a stage micrometre to determine the length of each division on an eye piece graticule.

Answer 86

The protein shell of a virus which encloses its genetic material. A lipid envelops with embedded attachment proteins often surround the capsid in some viruses.

Answer 87

A thick polysaccharide layer which can cover the outer layer of bacterial cell walls. The capsule prevents bacterial desiccation; helps to resist phagocytosis by macrophages and provides protection against bacterial viruses and hydrophobic toxins such as detergents

Answer 88

A protein which spans the plasma membrane. A carrier protein combines with a specific molecule such as glucose, causing the carrier protein to change shape so that the molecule is released to the inside of the membrane.

Answer 89

A sequence of changes during the lifespan of a cell, involving sequences of cell divisions separated by periods of cell growth. The cell cycle has three stages: interphase; nuclear division; cytokinesis. The length of the cell cycle varies for different types of cell e.g. bone marrow cells approx. 18 hours; yeast cells 1.3-3 hours.

Answer 90

The process used to break up cells and isolate their different organelles to study their structure and function.

Answer 91

T lymphocytes only respond to antigens that are presented on a body cell, rather than antigens within body fluids.

Answer 92

This is present in all plant cells and many members of the Protoctista and fungi. In plant cells, the cellulose cell wall consists of microfibrils made from chains of beta glucose monomers, held together by 1,4 glycosidic bonds. Hydrogen bonds occur between adjacent chains. Bundles of microfibrils form fibres embedded in a matrix of pectins and hemicelluloses. The cellulose cell wall provides mechanical strength to prevent the cell from bursting when water enters the cell by osmosis. Collectively cellulose cell walls provide mechanical strength to the whole plant and as cellulose is fully permeable, it allows water to pass along it to enable the movement of water through the plant. The cell walls of fungi are made of a nitrogen containing polysaccharide called chitin.

Answer 93

Centrioles are only found in animal cells and are constructed of microtubules arranged in nine triplets forming a cylinder. Centrioles occur in pairs near to the nucleus in a region called the centrosome. During cell division the centrosome organises spindle fibres [consisting of microtubules] to extend between the centrioles, to separate chromosomes and chromatids.

Answer 94

These form selective water filled hydrophilic channels across the membrane to allow specific water soluble ions to pass through

Answer 95

Double membrane bound organelle with its own DNA and 70S ribosomes, found in some plant cells. Photosynthesis occurs in this organelle.

Answer 96

Cholesterol molecules fit neatly within the phospholipid bilayer of the cell surface membrane. Cholesterol molecules add strength to the membrane; reduce lateral movement of other molecules; make the membrane less fluid at high temperatures and prevent leakage of water and dissolved ions from the cell.

Answer 97

Cilia [singular: cilium] are composed of microtubules arranged in a ring of nine pairs surrounding two central microtubules. Unlike flagella, cilia are shorter and are always present in large numbers on the surface of cells. Cilia play a role in the locomotion of protists such as Paramecium. Cilia move liquids across the surface of cells which is turn helps to remove contaminants such as mucus and bacteria in the respiratory tract; cilia play a role in the movement of the secondary oocyte in the oviduct towards the uterus.

Answer 98

Pleural is cisternae. A series of flattened tubular membranes found in the endoplasmic reticulum and Golgi apparatus.

Answer 99

Small groups of identical B cells and T cells undergo cell division by mitosis to produce effector cells such as plasma cells and memory cells, during an immune response

Answer 100

The process during the immune responses when specific clones of B cells and/or T cells interact with antigens displayed on APC's.

Answer 101

A group of genetically identical cells. In the immune response, there are clones of B cells and clones of T cells. Each clone has its own unique cell surface receptor complementary to a specific antigen.

Answer 102

The movement of molecules or ions using a concentration gradient which has already been set up by direct active transport e.g. the movement of glucose or amino acids into intestinal epithelial cells along with sodium ions that have been actively transported out by the sodium - potassium pump.

Answer 103

Diseases caused by a pathogen which is transmitted from one host organism to another.

Answer 104

Consists of a sequence of amino acids which remains the same in all antibodies of the same class. Constant regions bind to receptors on the surface of phagocytes. This helps phagocytes detect pathogens which have been 'labelled' by antibodies, prior to pathogen destruction by phagocytosis

Answer 105

Folding in the inner mitochondrial membrane to provide a large surface area for the attachment of enzymes and other proteins involved in aerobic respiration.

Answer 106

Small protein molecules that act as cell signalling compounds. Many of them are involved in stimulating B cells to divide and develop into plasma cells and memory cells. Some T helper cells secrete cytokines that stimulate macrophages to carry out phagocytosis more aggressively. Interleukins are included in the cytokine group.

Answer 107

In animal cells, the cytoplasm near the equator tucks inwards to divide the cytoplasm. The organelles are shared between the two cells and the Golgi apparatus produces vesicles that form the new section of the plasma membrane

Answer 108

Located within the cytoplasm and consists of microtubules and microfilaments. The cytoskeleton is responsible for (i) cellular movement using flagella and/or cilia; (ii) intracellular movement so that organelles can move from one part of the cell to another; (iii) supports organelles and provides a scaffolding that strengthens the cell.

Answer 109

Type of T cell that kills abnormal cells and body cells that are infected by pathogens, by producing a protein called perforin that makes holes in the cell surface membrane. The cell membrane becomes freely permeable to all substances.

Answer 110

A large phagocytic cell with lengthy extensions to give a large surface area to interact with pathogens and with lymphocytes.

Answer 111

The net movement of molecules [or ions] from a region where they are more highly concentrated to one where their concentration is lower until evenly distributed. Molecules [or ions] move down a concentration gradient.

Answer 112

The transfer of a pathogen from an infected organism to an uninfected organism.

Answer 113

Enzyme linked immunosorbent assay'. This is a plate based technique designed to detect and quantify peptides, proteins, antibodies, and hormones in a sample. ELISA can be used to detect HIV and other pathogens which cause TB and hepatitis, as well as in drug and allergen tests. In ELISA, an antigen must be immobilised to a solid surface and then complexed with an antibody, linked to an enzyme. A coloured product is produced. The intensity of the colour is relative to the amount of antigen present.

Answer 114

The process by which cells absorb large quantities of materials by engulfing them. An active process requiring ATP. There are two forms: phagocytosis and pinocytosis.

Answer 115

Cells which have a membrane bound nucleus and organelles such as mitochondria; chloroplasts; RER; Golgi apparatus; 80s ribosomes and linear DNA associated with histones.

Answer 116

The reverse of endocytosis. An active process requiring ATP. Secretory vesicles fuse with the cell membrane to release substances from the cell.

Answer 117

Within an organism but not inside cells e.g. tissue fluid; blood; lymph

Answer 118

A peripheral globular protein which occurs on one side of the plasma/cell surface membrane.

Answer 119

A circular disc fitted into the eyepiece of a microscope, which has a scale marked on it with equal divisions in arbitrary units. The length of each division varies as the objective lens is changed.

Answer 120

The movement of charged ions and large polar molecules such as glucose and amino acids, through transmembrane protein channels or protein carrier molecules that span the membrane. A passive process.

Answer 121

First stage of interphase. The chromosomes are checked for damage. Cell organelles [other than chromosomes ] are replicated

Answer 122

When a plant cell is not turgid but has not yet plasmolysed.

Answer 123

Flagella [singular: flagellum] are composed of microtubules arranged in a ring of nine pairs surrounding two central microtubules. Flagella are found in some single cell organisms where they move the cell around e.g. Euglena; Chlamydomonas. A flagellum also forms the tail of motile sperm cells.

Answer 124

The structure of the plasma membrane. Consists of a dynamic phospholipid bilayer, scattered with moving transmembrane and peripheral globular proteins. Glycolipids, glycoproteins and cholesterol molecules are also scattered throughout.

Answer 125

Short branching carbohydrate chain is covalently bonded to a phospholipid in the membrane. Glycolipids act as recognition sites, help to maintain membrane stability and help cells attach to one another to form tissues.

Answer 126

An extrinsic globular protein in the membrane which has a short branching carbohydrate chain attached. Glycoproteins act as recognition sites and cell-surface receptors e.g. for hormones and neurotransmitters.

Answer 127

Consists of a series of unconnected flattened membranous sacs called cisternae and Golgi vesicles. The functions of the Golgi apparatus are to (i) modify proteins and lipids from the RER and prepare them for secretion. (ii) produce secretory enzymes (iii) form lysosomes

Answer 128

A stack of thylakoid membranes, containing chlorophyll pigments which absorb light energy during cyclic and non-cyclic photophosphorylation.

Answer 129

Type of T cell that coordinates an immune response by stimulating the responses of B cells and cytotoxic T cells by producing chemical signals such as interleukins.

Answer 130

Known as population immunity. When sufficient numbers in a population are immune to an infectious disease, either through vaccination or exposure to the pathogen, these people provide a barrier to further pathogen transmission to those individuals who are not vaccinated or have low functioning immune systems.

Answer 131

The process used to break open cells to release the organelles from the cell. The process uses a blender/homogeniser and cold, isotonic buffered solution.

Answer 132

B lymphocytes produce specific antibodies in response to specific antigens present on the surface of a pathogen, foreign cell, toxin, damaged or abnormal cell circulating in the blood and tissue fluid

Answer 133

Polar; 'water-loving'.

Answer 134

Non-polar; 'water-hating'.

Answer 135

A period of considerable cellular activity within the cell cycle when the cell is not dividing. Consists of G1 phase, when cell organelles except chromosomes replicate; S phase when DNA is replicated; G2 phase when DNA is checked for errors.

Answer 136

Within a cell

Answer 137

A transmembrane globular protein which spans the membrane and is exposed at both surfaces.

Answer 138

Folding in of the plasma membrane to form a pocket

Answer 139

Based on a conventional optical microscopy and used to enhance optical resolution. Cells are stained with fluorescent dyes. A thick section of tissue or small living organism is scanned with a laser beam, which is reflected by the dyes to produce a computerised 3D image

Answer 140

Membrane bound vesicles, which lack an internal structure, produced by the Golgi apparatus. They contain a variety of digestive enzymes which can break down proteins, carbohydrates, lipids and nucleic acids. Lysosomes hydrolyse material ingested by phagocytosis; break down damaged and/or dead cells and organelles [autolysis]; release enzymes by exocytosis to destroy material around the cell.

Answer 141

A type of enzyme presents in lysosomes. Lysozymes hydrolyse the cell walls of ingested bacterial once lysosomes have fused with phagosomes during phagocytosis.

Answer 142

A large long lived phagocytic cell that remains in tissues. Macrophages process pathogens and present antigens to T lymphocytes.

Answer 143

The ability of a lens to enlarge the size of an object. Calculated by dividing the image size by the real size of the object.

Answer 144

The interior solution in the mitochondria. It contains lipids, and enzymes involved in the Krebs cycle. Mitochondrial DNA and 70S ribosomes allow the production of some mitochondrial proteins.

Answer 145

Lymphocytes which develop during the primary immune response and retain the ability to antibodies quickly when an antigen enters the body on a second, or subsequent occasion.

Answer 146

Spindle fibres of microtubules form and the centromere of each chromosome attaches to the equator of the spindle.

Answer 147

An SI unit of measurement which is one thousandth of a millimeter

Answer 148

Microtubules are small tubular structures in the cytoplasm, composed of the polymer tubulin, a globular protein that is arranged in spirals. Microtubules form part of the cytoskeleton, which provides structure and support in eukaryotic cells.

Answer 149

Finger like projections of the cell surface membrane, about 0.6μm in length. Often described as a 'brush border'. Used to increase the surface area of the cell surface membrane.

Answer 150

Mitochondria [pleural]. Double membrane bound organelle with its own DNA and 70S ribosomes, found in most eukaryotic cells. Site of aerobic respiration e.g. the Krebs cycle and oxidative phosphorylation.

Answer 151

Cell division which produces two identical daughter cells with the same number of chromosomes as the parent cell. Important in growth, replacement and repair of cells; asexual reproduction; production of stem cells; tumours.

Answer 152

A single type of antibody produced by a clone of plasma cells, which have originated from a specific B lymphocyte. Monoclonal antibodies have uses in medical diagnosis e.g. prostate cancer; pregnancy testing and therapeutic drug treatment for cancer

Answer 153

A larger cell than a neutrophil that circulates in the blood and leaves to remain as a long lived macrophage in tissues such as the lungs.

Answer 154

A polymer of sugars and amino acids used to produce a mesh like layer which forms bacterial cell walls. Otherwise known as peptidoglycan.

Answer 155

An SI unit of measurement which is one thousandth of a micrometer

Answer 156

Results from an individual becoming infected with a pathogen under normal natural circumstances. The body produces its own antibodies and may continue to do so for many years.

Answer 157

This occurs when antibodies cross the placenta during pregnancy and when a young child is breast fed by its mother. No direct contact with the antigen is required to produce immunity. Antibodies are not replaced when they are broken down and no memory cells are formed so there is no lasting immunity.

Answer 158

A short lived phagocytic cell produced in the bone marrow that circulates in the blood. They have lobed nuclei and granular cytoplasm.

Answer 159

Diseases not caused by pathogens and have numerous causes e.g. Genetic; degenerative; deficiency and lifestyle.

Answer 160

A darkly stained region within the nucleus, responsible for the manufacture of ribosomal RNA and hence ribosomes.

Answer 161

Present in eukaryotic cells and consists of chromatin. Chromatin is a complex of DNA and histone proteins. DNA, provides the template for making RNA. The nucleus indirectly controls the activities of the cell. Chromatin exists in two forms: lighter, less condensed euchromatin and darker, more condensed heterochromatin.

Answer 162

A collection of tissues combined and coordinated together to perform a specific function e.g. heart; leaf; stomach.

Answer 163

A collection of organs which work together as a single unit, to perform specific functions more efficiently e.g. digestive system to digest and process food; respiratory system for breathing and Organisms Exchange Substances with Their Environment.

Answer 164

A specialised part of a cell that performs a particular function.

Answer 165

The diffusion of water molecules from a region of high water potential to a region of lower water potential across a partially permeable membrane.

Answer 166

A disease causing organism; many are microorganisms such as viruses, bacteria, fungi and Protoctista.

Answer 167

The uptake of solid material into cells. Pseudopodia project from the cell, surround the solid material e.g. microbe, to encapsulate the material into a phagocytic vesicle/ vacuole. 'Cell eating'.

Answer 168

A phagocytic vesicle containing the engulfed pathogen.

Answer 169

Short, thin hair like structures composed of protein, which are present on the surface of many bacteria and archaea. Pili have a role in movement, adherence to cell surfaces and in the formation of conjugation tubes, which allow exchange of genetic material between bacterial cells.

Answer 170

Method by which small particles and liquids are taken into cells. The plasma membrane invaginates to form very small vesicles. 'Cell drinking'.

Answer 171

An activated B cell that makes and releases antibodies during the immune response.

Answer 172

Gaps in plant cell walls through which cytoplasmic strands connect the protoplast of one cell with an adjacent cell.

Answer 173

The shrinking of the cytoplasm away from the cell wall of a plant cell, when water is lost due to osmosis when the water potential of the surrounding solution is lower than the cell

Answer 174

The production of antibodies for the first time by plasma cells, following exposure to a foreign antigen

Answer 175

Cells with no membrane bound nucleus or membrane organelles. Cell wall made of murein; circular DNA not associated with proteins; additional circular DNA plasmids may be present; ribosomes are smaller [70s]. Mucilaginous capsule may be present.

Answer 176

DNA undergoes supercoiling and chromosomes are visible as two sister chromatids held together by a centromere. The nucleolus has disappeared and the nuclear membrane has broken down.

Answer 177

The part of a cell contained within the plasma membrane; the nucleus and the cytoplasm [excluding large vacuoles].

Answer 178

Protrusions of the cell membrane which resemble 'false feet'. Formed during phagocytosis. Pseudopodia extend and surround large particles or microbes, to seal them into a vesicle.

Answer 179

The ability of a microscope to distinguish two adjacent points as separate from each other.

Answer 180

A virus such as HIV, with single stranded RNA. When a retrovirus invades a host cell, it uses its enzyme reverse transcriptase to make DNA from an RNA template

Answer 181

An enzyme which catalyses the conversion of RNA into DNA

Answer 182

A ribosome consists of a large and small subunit, containing ribonucleic acid [rRNA] and protein. Ribosomes are the site of protein synthesis and are located in the cytosol of eukaryotic and prokaryotic cells, as well as on RER in eukaryotic cells. Ribosomes in eukaryotic cells are larger and referred to 80s as opposed to 70s ribosomes in prokaryotes

Answer 183

An elaborate three dimensional series of sheet like membranes which are continuous with the outer nuclear envelope, which form a system of flattened cisternae. RER has ribosomes present on the outer surfaces of the cisternae to produce proteins destined for transport and secretion. RER provides a large surface area for protein and glycoprotein synthesis as well as a pathway for the transport of materials especially proteins to the Golgi apparatus for further processing.

Answer 184

A focussed beam of electrons is passed across the surface of the specimen to produce a three dimensional view of the surface. Maximum magnification is x100 000 and maximum resolution is 10nm.

Answer 185

DNA is checked for damage that may have occurred during replication. The cycle may be delayed to repair the DNA.

Answer 186

The production of antibodies by memory cells, following a second or subsequent exposure to the original antigen. Response is quicker, more antibody molecules are produced and the response lasts for longer

Answer 187

SER lacks ribosomes on its surface and is often more tubular in appearance. Its functions are to (i) synthesise, store and transport lipids and phospholipids (ii) synthesise steroids such as cholesterol and reproductive hormones. (iii) synthesise, store and transport carbohydrates; (iv) detoxify lipid soluble drugs.

Answer 188

This is used to calibrate the scale on the eye piece graticule for each objective lens used. The micrometer slide has a scale engraved into it, calibrated in known divisions e.g. 0.1mm

Answer 189

The colourless thick fluid which surrounds the grana in the chloroplasts. The light independent stage or Calvin cycle takes place in the stroma. Starch grains are also present in the stroma.

Answer 190

DNA undergoes semi-conservative replication. A check is made that all chromosomes have replicated. If they have not, the cell cycle is stopped.

Answer 191

Type of white blood cell which originates in bone marrow but matures in the thymus gland. When T cells respond during an immune response, they do not make and release antibodies.

Answer 192

The spindle fibres disintegrate and new nuclear membranes form around each group of chromosomes. New nucleoli form in each daughter nucleus

Answer 193

A complex arrangement of internal membranes which are grouped into stacks called grana [singular: granum], joined by intergranal lamellae. Chlorophyll pigments which absorb light energy, are located on the thylakoid membranes.

Answer 194

A collection of similar cells which perform a specific function e.g. epithelial tissue; xylem.

Answer 195

A beam of electrons focussed by electromagnets pass through ultra-thin dead tissue samples. Capable of a maximum magnification of x500 000 and a resolution of 0.2nm.

Answer 196

The protoplast of a plant cell is pushed against the cellulose cell wall when water enters the cell by osmosis. When the pressure of the protoplast equals the resistive force of wall pressure, no further water enters the cell and the cell is described as fully turgid.

Answer 197

Process which follows homogenisation. Fragments in the filtered homogenate are spun at different speeds in a centrifuge to separate different types of organelles from each other.

Answer 198

A biological preparation that produces artificial active immunity. A vaccine often contains a weakened or dead form of the pathogen, its toxin or one of its' surface proteins.

Answer 199

A membrane bound organelle found in plant and fungal cells/hyphae. Functions include: providing structural support in stems; leaves and flowers; growth and cell expansion in germinating seeds; isolation of toxic or waste materials; maintenance of an acidic internal pH.

Answer 200

Antigen binding site on an antibody/immunoglobulin

Answer 201

Acellular non-living particles which are smaller than bacteria, between 20-300nm. Consist of DNA or RNA enclosed within a protein coat called a capsid.

Answer 202

This is represented by the Greek letter psi [ψ] and is measured in units of pressure, usually kilopascals [kPa]. It is measure of the relative tendency of water to move from one area to another. Water moves from a higher water potential to a lower water potential. Pure water has a water potential of zero at 25oC and 100kPa. The more solute added to water, the lower [or more negative] the water potential

Answer 203

The movement of digested food molecules across the wall of the small intestine/ ileum into the blood or lymph.

Answer 204

Water molecules stick to the walls of xylem vessels. This helps to maintain the column of water in position even when transpiration is not taking place e.g. at night. Without adhesion, the force of gravity could cause the water column to drop.

Answer 205

[singular alveolus]. Known as air sacs. Arranged in groups at the end of the smallest bronchioles. The alveoli are lined with a single layer of epithelium [which acts as a gas exchange surface] but there is also an extracellular matrix of collagen and elastic fibres between the alveoli. The elastic fibres allow the alveoli to expand during inspiration and recoil during expiration.

Answer 206

A type of carbohydrase enzyme which breaks down starch to maltose

Answer 207

The main artery which divides into three above the heart. Aorta carries oxygenated blood from the left ventricle under high pressure to all parts of the body except the lungs.

Answer 208

The movement of water through the cell walls of plant cells. The cell walls are readily permeable and the pathway offers little resistance to the flow of water.

Answer 209

As blood flows further from the heart, arteries branch into smaller blood vessels called arterioles. Arterioles regulate blood flow. They have a relatively thicker layer of smooth muscle than arteries and when this contracts it narrows the arteriole and restricts blood flow. The smooth muscle is controlled by the autonomic nervous system. Arterioles have a relatively thinner layer of elastic tissue because blood pressure is lower.

Answer 210

A blood vessel which usually carries oxygenated blood away from the heart. They have a narrow lumen and blood is under high pressure. The outer tunica adventitia/externa of collagen is relatively thinner in arteries than veins. Arteries have a thick tunica media of smooth muscle and elastic tissue and a thin smooth inner lining [endothelium] which reduces friction to allow blood to flow freely. The overall thickness of the artery wall is greater than in veins, to resist the vessel bursting under pressure.

Answer 211

[pleural atria]. A top thin walled chamber of the heart. The right atrium receives deoxygenated blood from the superior and inferior vena cava. The left atrium receives oxygenated blood from the pulmonary veins.

Answer 212

The valve between the left atrium and left ventricle. Sometimes known as the left atrioventricular valve.

Answer 213

One of the primary components of bile, produced by the liver and stored in the gall bladder. Aid the absorption of fat soluble vitamins i.e. A, D, E and K . Bile salts emulsify lipids into tiny droplets called micelles. This increases the surface area of the lipids to speed up the action of lipases.

Answer 214

A decrease in pH and an increase in carbon dioxide concentration lowers the affinity of haemoglobin for oxygen. The oxygen dissociation curve for haemoglobin shifts to the right at any given partial pressure of oxygen.

Answer 215

The number of breaths per minute [a breath is taking air in and breathing it out]

Answer 216

These are numerous, thin, narrow branches of the bronchi. They do not have cartilage rings. The walls are lined with smooth muscle so that larger bronchioles can control the flow of air in and out of the alveoli [air sacs]. Smaller bronchioles have no goblet cells or cilia on their epithelium.

Answer 217

[plural bronchi]. Bronchi are two divisions of the trachea, each leading to one lung. They are similar in structure to the trachea although they have a smaller diameter and thinner walls. The bronchi have complete rings of cartilage to support them.

Answer 218

Known as the oral cavity or mouth in animal anatomy

Answer 219

Small, numerous blood vessels responsible for the exchange of materials with cells. They have a small narrow lumen which slows blood flow to enable a longer time for materials to be exchanged. There are spaces [intercellular junctions] between endothelial cells to allow white blood cells to escape to combat infections within tissues.

Answer 220

A type of enzyme which breaks down carbohydrates ultimately to monosaccharides by hydrolysis.

Answer 221

The contraction and relaxation of heart muscle in a regular cycle. The cycle consists of sequences of systole followed by diastole. The atria contract followed by the ventricles and then there is a short period of relaxation before the cycle starts again.

Answer 222

The volume of blood pumped by one ventricle of the heart in one minute. It is usually measured in dm3 min-1. Cardiac output = heart rate x stroke volume

Answer 223

A form of connective tissue that provides strengthening and support. It is composed of cells surrounded by a matrix of complex polysaccharides and amino groups. Cartilage is resistant to tension and compression. It is not as strong as bone but is more flexible than bone.

Answer 224

A continuous band which goes around the wall of endodermal cells in the root. It is made of suberin, a waxy, waterproof substance.

Answer 225

A large structural polysaccharide made from chains of modified glucose. Chitin is found in the exoskeletons of insects, as rings around the outside of insect tracheae and in the hyphal walls of many fungi species.

Answer 226

Special particles adapted for the transport of lipids through epithelial cells of the ileum. They are formed when triglycerides associate with cholesterol and lipoproteins in the endoplasmic reticulum and Golgi apparatus

Answer 227

A layer of cells which forms a covering or lining which possess tiny hairs or cilia on its surface. The cilia of ciliated epithelium beat constantly to remove mucus towards the top of the trachea.

Answer 228

A circulatory system in which blood circulates entirely within blood vessels.

Answer 229

Water molecules are polar and form hydrogen bonds between one another and hence tend to stick together. Cohesion forces help to maintain a continuous column of water in xylem vessels.

Answer 230

A structural fibrous protein which on boiling yields gelatine. Found in skin, tendons; cartilage; teeth and the walls of blood vessels. A collagen molecule consists of three polypeptide chains in the shape of a helix, wound around each other to form a three stranded 'rope'. Collagen has a high tensile strength.

Answer 231

The longest part of the large intestine, which is connected to the small intestine at one end and the anus at the other. Responsible for the reabsorption of water and some electrolytes from partially digested food.

Answer 232

A cell closely associated with a phloem sieve tube element, directly linked via many plasmodesmata. Companion cells appear to regulate the activity of sieve tube elements and play a role in the loading and unloading of sucrose.

Answer 233

Blood vessel which supplies oxygenated blood to cardiac muscle.

Answer 234

Blood vessel which returns deoxygenated blood from heart muscle [myocardium] to the right atrium.

Answer 235

The flow of blood through the gill lamellae is in the opposite direction to the flow of water over the gills. This maintains a steep diffusion gradient between the water and the blood, so maximising the oxygen that can be extracted from water.

Answer 236

The form of haemoglobin without oxygen.

Answer 237

The period of time when the heart muscle is relaxed.

Answer 238

The breakdown of large complex insoluble food molecules into simpler, smaller, soluble ones. The process can occur mechanically e.g. in the mouth using teeth, and chemically using hydrolytic enzymes.

Answer 239

Enzymes which break/hydrolyse the peptide bond between two amino acids of a dipeptide. Dipeptidases are membrane bound and part of the cell surface membrane of the epithelial cells of the ileum.

Answer 240

Blood passes through the heart twice during each circuit of the body.

Answer 241

The act or process of removing undigested or waste material from a cell or organism e.g. defaecation

Answer 242

These are found in all lung tissues, including the alveoli. As expiration is a passive process, elastic fibres provide elasticity to enable recoil of the lungs during expiration

Answer 243

The process of splitting lipids [fats and oils] into tiny droplets called micelles, by bile salts.

Answer 244

Enzymes which break/hydrolyse peptide bonds between amino acids in the central part of a protein molecule, forming a series of shorter peptide chains.

Answer 245

Collectively these form a single cell layer which lines all blood vessels. Signals from endothelial cells organise the growth and development of connective tissue containing collagen, that forms the surrounding layers in the tunica externa/blood vessel wall.

Answer 246

Enzymes which break/hydrolyse peptide bonds on the terminal amino acid of the shorter peptide molecules formed by endopeptidases. The action of exopeptidases produces dipeptides and individual amino acids.

Answer 247

An alternative word for 'breathing out'. Largely a passive process. The internal intercostal muscles contract and the rib cage moves down and inwards. The diaphragm muscles relax and the diaphragm is pushed up again by the contents of the abdomen.

Answer 248

Muscle which lies between the ribs. External intercostal muscles contract during inspiration to move the rib cage upwards and outward. During expiration, the external intercostal muscles relax

Answer 249

Gills are the gas exchange organs of bony fish. Each gill is made up of a series of stacked membranes which protrude from the gill arch. Gill filaments increase the surface area of each gill for gas exchange.

Answer 250

Sometimes called a gill plate. Each gill lamella occurs at right angles on a gill filament. Gill lamellae increase the surface area of each gill filament for gas exchange.

Answer 251

These cells line the trachea, bronchi and larger bronchioles. Goblet cells are located between ciliated cells of the epithelium. Goblet cells secrete mucus.

Answer 252

A globular protein found in erythrocytes/ red blood cells. Consists of four polypeptide chains, each associated with a haem group containing an Fe2+ ion. Each Fe2+ ion can combine with a single oxygen molecule [O2] to form oxyhaemoglobin. Haemoglobin carries oxygen from the lungs to body tissues and returns carbon dioxide from the tissues back to the lungs

Answer 253

The number of times the heart beats in one minute. Measured as beats per minute.

Answer 254

Plants which are adapted to live in fresh water [with leaves floating on the surface or beneath the surface].

Answer 255

The pressure exerted by a fluid. A pressure is created by the pumping action of the heart at the arterial end of capillaries which tends to force fluid out of the plasma into the intercellular spaces to form tissue fluid.

Answer 256

The longest part of the small intestine. Contains crypts of Lieberkühn which secrete the maltase; sucrase; exopeptidases; endopeptidases. The inner walls are folded into villi to give a large surface area for absorption. The surface area is further increased by microvilli on the epithelial cells of each villus.

Answer 257

An alternative word for 'breathing in'. An active process involving the contraction of the external intercostal muscles to move the rib cage up and outwards, whilst the muscles of the diaphragm contract causing it to flatten

Answer 258

Muscle which lies between the ribs. Internal intercostal muscles relax during inspiration. During expiration, the internal intercostal muscles contract to move the rib cage down and inwards.

Answer 259

Two or more forms of the same element with the same number of protons but different numbers of neutrons in their nuclei. Isotopes differ in their relative atomic mass and physical properties. Many isotopes are radioactive and used in tracer experiments in living tissues.

Answer 260

An enzyme which hydrolyses the single glycosidic bond in a lactose molecule. This hydrolysis produces the monosaccharides, glucose and galactose.

Answer 261

Capillary like structures found in the lymphatic system.

Answer 262

Absorbs water [by osmosis], minerals and vitamins. Faeces are stored in the rectum and egested through the anus.

Answer 263

A type of enzyme produced in the pancreas which hydrolyses the ester bond found in triglycerides to form fatty acids and monoglycerides. A monoglyceride is a glycerol molecule with a single fatty acid attached.

Answer 264

An extensive network of lymph vessels and lymph nodes throughout the body which carry fluid called lymph. The system works closely with the cardiovascular system and plays a role in the immune response; collection and return of fluid/proteins to the blood; absorption of chylomicrons.

Answer 265

An enzyme which is part of the cell surface membranes of the epithelial cells lining the ileum. Often referred as a 'membrane bound disaccharides'. Maltase hydrolyses maltose into alpha glucose.

Answer 266

The current model of translocation in phloem. Divided into three phases: 1. Transfer of sucrose into sieve tube elements from photosynthesising tissue. 2. Bulk movement of sucrose through sieve tube elements 3. Transfer of sucrose from sieve tube elements into storage or other sink cells.

Answer 267

Tiny spheres of bile salts surrounding long chain fatty acids and monoglycerides.

Answer 268

Another name for the gullet. A tube which carries food from the mouth to the stomach.

Answer 269

A form of osmotic pressure exerted by blood proteins e.g. albumin that tends to pull water from the tissue fluid into the blood plasma.

Answer 270

A flap of tissue that covers the gills in bony fish.

Answer 271

A graph which shows the relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen.

Answer 272

The volume of oxygen consumed by the subject. The spirometer removes carbon dioxide from the re-breathed air, therefore the volume of air gradually decreases as oxygen is extracted from it. The change in volume on the spirometer trace, is a measure of oxygen uptake.

Answer 273

The form of haemoglobin combined with oxygen.

Answer 274

A layer of columnar cells rich in chloroplasts found beneath the upper epidermis of a leaf

Answer 275

[plural: plasmodesmata]. A microscopic channel through plant cell walls, connecting the cytoplasm of two cells. These are lined with plasma membrane. Sieve tube elements and companion cells are connected by plasmodesmata, to allow transport of molecules during translocation.

Answer 276

Used to measure the rate of water uptake in a cut plant shoot. It is assumed that the rate of water uptake is directly proportional to the rate of water loss by transpiration.

Answer 277

This transfers deoxygenated blood from the right ventricle to the lungs for gas exchange.

Answer 278

These transfer oxygenated blood from the lungs to the left atrium of the heart.

Answer 279

The final section of the large intestine. Faeces are stored here before periodically being removed through the anus.

Answer 280

The volume of air that remains in the lungs after maximum forceful expiration. It is the volume of air that cannot be expelled and keeps the alveoli open at all times.

Answer 281

A force that drives water upwards in xylem vessels. It is primarily generated by osmotic pressure in root cells and can be demonstrated by exudation of fluid in a cut stem, just above soil level.

Answer 282

A valve which occurs at the base of the aorta and pulmonary artery to prevent backflow of blood into the ventricles. Alternative names include the aortic valve and the pulmonary valve.

Answer 283

Living cells which form continuous tubes within phloem tissue. Each sieve tube element is associated with a companion cell. Sieve tube elements have no nucleus, few organelles and very little cytoplasm to aid their ability to transport assimilates such as sucrose, amino acids and mineral ions.

Answer 284

An area of a plant above or below photosynthesising leaves where sucrose is taken out of the phloem e.g. developing potato tuber; nectary; meristems.

Answer 285

This is found in the trachea, bronchi and the larger bronchioles. It maintains the tone of the airways and also allows expansion in conditions when extra oxygen is needed e.g. during exercise.

Answer 286

An area of a plant in which sucrose is loaded into phloem e.g. leaf; stem.

Answer 287

An opening or pore found on each side of an insect's abdomen which allows gases to enter and leave tracheae. Each abdominal segment of the insect, has a pair of spiracles. Spiracles can be opened and closed by valves.

Answer 288

Equipment that can be used to measure vital capacity; tidal volume; breathing rate and oxygen uptake. A spirometer produces a trace on a revolving drum called a kymograph or electronically on a screen.

Answer 289

Leaf tissue consisting of loosely arranged rounded parenchyma cells containing chloroplasts. Situated below the palisade mesophyll layer on the lower side of the leaf. Spongy mesophyll layer contains air spaces to enable diffusion of carbon dioxide and oxygen through the leaf.

Answer 290

[Pleural stomata.] A pore in the epidermis of a leaf, surrounded by a pair of guard cells.

Answer 291

A muscular organ with an inner layer that produces protein digesting enzymes and hydrochloric acid.

Answer 292

The volume of blood pumped out from the left ventricle during each systolic heart contraction. Measured in mL

Answer 293

A waterproof, waxy macromolecule which forms the Casparian strip in endodermal root cells. Suberin also plays a role in bark formation in woody non herbaceous plants as well as acting as a sealing tissue following wounding and leaf abscission.

Answer 294

An enzyme which hydrolyses the single glycosidic bond in a sucrose molecule. This hydrolysis produces the monosaccharides, glucose and fructose.

Answer 295

The movement of water through the cell cytoplasm and from cell to cell via plasmodesmata.

Answer 296

Systole represents the time when the heart muscle contracts. Systole can be divided as atrial systole when the atrial walls contract, forcing the remaining blood into the ventricles from both atria. Ventricular systole occurs when the left and right ventricles contract to expel blood into the aorta and pulmonary artery.

Answer 297

The volume of air that is normally breathed in or out at rest.

Answer 298

Known as interstitial or extracellular fluid. It is fluid which surrounds cells consisting of water, ions, dissolved gases and soluble molecules such as glucose. It facilitates the exchange of nutrients and waste products.

Answer 299

A wide flexible tube in the human respiratory system. Known as the windpipe. Contains C- shaped rings of cartilage to provide 'scaffolding' to keep the tube open. The tracheal walls are made up of smooth muscle, lined with ciliated epithelial cells that contain goblet cells which secrete mucus.

Answer 300

[singular trachea]. Form the basis of the gas exchange system in insects. An internal network of tubes strengthened by a series of rings made of chitin. Carry atmospheric air with oxygen to respiring tissues.

Answer 301

Smaller dead ended tubes which branch from larger tracheae. Tracheoles contain a small amount of tracheal fluid at the end. Tracheoles extend throughout all body tissues of the insect and carry oxygen to body cells.

Answer 302

The transport of dissolved photosynthetic assimilates and mineral ions in phloem tissue in plants e.g. sucrose, amino acids; potassium ions; chloride ions; phosphate and magnesium ions.

Answer 303

The loss of water vapour, by diffusion down a water potential gradient from the air spaces in the spongy mesophyll to the environment outside. Most transpiration occurs through stomata on the leaves and is a natural consequence of gas exchange and photosynthesis requirements

Answer 304

The uninterrupted flow of water and solutes that is taken up by the roots and transported via the xylem vessels to the leaves, where it evaporates into the sub-stomatal cavity.

Answer 305

The valve between the right atrium and right ventricle. Sometimes known as the right atrioventricular valve.

Answer 306

A blood vessel which usually carries deoxygenated blood from capillaries back to the heart. They have a wide lumen and blood is under low pressure. The outer tunica adventitia/externa of collagen is relatively thicker in veins than arteries. Veins have a thinner tunica media of smooth muscle and elastic tissue and a thin smooth inner lining [endothelium] which reduces friction to allow blood to flow freely. Veins possess valves throughout to ensure one way flow towards the heart.

Answer 307

The main vein which returns deoxygenated blood from the tissues of the body to the right atrium

Answer 308

The two bottom larger chambers of the heart. The left ventricle has a much thicker muscular wall than the right ventricle.

Answer 309

These are the smallest types of vein. Blood flows out of capillaries into venules, which then join together to form larger veins. The smallest venules consist only of an endothelium but the larger ones have a similar structure to veins but scaled down with fewer or no elastic fibres.

Answer 310

The maximum volume of air that can be breathed in or out of the lungs in a single breath.

Answer 311

Plants which live in dry conditions which have restricted water supply. These plants have extra adaptations to reduce water loss e.g. fewer &/or sunken stomata; rolled leaves; hairy leaves; thicker waxy cuticle.

Answer 312

Plants which live in dry, arid conditions and have extra adaptations to reduce water vapour loss.

Answer 313

A type of cell found in xylem tissue responsible for transporting water and mineral ions from the roots upwards. Xylem vessel elements have lost their end walls to allow the free passage of water to the next cell. The cell is dead and has no cytoplasm to enable water to move through more easily. The cell wall is thickened with lignin which makes it rigid and able to give support. Pits allow water to move sideways from cell to cell. Pits are areas where the cell wall is not thickened with impermeable lignin.

Answer 314

A variant of a gene that is found at the same locus on the chromosome and codes for the same polypeptide as another allele for the same gene. The polypeptides coded by different alleles may differ by one or more amino acids.

Answer 315

The number of times an allele occurs within the gene pool

Answer 316

A triplet of complementary bases to the mRNA codon, carried on tRNA.

Answer 317

A group of single celled prokaryotes that were originally classified as bacteria. They are different from bacteria as a) histone proteins are associated with DNA b) membranes contain fatty acid chains attached to glycerol by ether linkages c) they have no murein in their cell walls d) introns are present in some genes e) contain several types of RNA polymerase.

Answer 318

Divides organisms according to differences that are useful at the time i.e. analogous characteristics such as colour, size, number of legs. For example, wings of butterflies and birds are both used for flight but they have different evolutionary origins

Answer 319

A large white sheet is placed on the ground or supported by struts and held below a tree. The tree is shaken to dislodge the animals. Very small animals can be collected from the beating tray with a pooter.

Answer 320

A system of naming species in which each species has two names: a generic name and a specific epithet e.g. Homo sapiens

Answer 321

The number of different ecosystems and habitats in an area, the number of species within those ecosystems and the genetic variation within each species.

Answer 322

The mass of biological material measured as wet mass or, more often dry mass to overcome fluctuations in water content.

Answer 323

[pleural chiasmata]. The point of contact during crossover of non-sister chromatids of homologous chromosomes during prophase 1 of meiosis. The process can result in the exchange of alleles and is much more frequent during meiosis than mitosis.

Answer 324

One of two strands held together by a centromere in a chromosome, once DNA has replicated during the S phase of interphase. They become visible at prophase and metaphase of mitosis or meiosis.

Answer 325

A thread like structure made from a long single helix of DNA combined with proteins called histones. The DNA - histone complex is coiled and the coils fold to form loops. The loops coil and pack together to form a chromosome. Chromosomes carry genetic information.

Answer 326

Changes in the structure or number of Genetic diversity chromosomes in a cell

Answer 327

A triplet of bases found on mRNA, that codes for a single amino acid.

Answer 328

An ecological term for a group of populations of two or more species which occupy the same geographical area at the same time.

Answer 329

The genetic code where amino acids are each coded for by more than one triplet of bases except for methionine and tryptophan.

Answer 330

A nucleic acid found in the nuclei of eukaryotic cells and in mitochondria and chloroplasts. Made from two polynucleotide chains held together by hydrogen bonds between complementary base pairs, so forming a double helix. Each nucleotide consists of a phosphate group, a pentose sugar, deoxyribose and one of four organic bases [adenine, guanine, thymine and cytosine]. DNA provides the long term storage of genetic information; the sequence of bases code for the assembly of amino acids to make polypeptides.

Answer 331

A cell that contains two copies of each chromosome.

Answer 332

A type of selection that favours one extreme of the range of phenotypes so the population changes over time

Answer 333

The highest taxonomic rank above the rank of kingdom introduced by Carl Woese in 1990, giving greater weight to molecular biology. There are three domains: Bacteria; Archaea and Eukarya.

Answer 334

An ecological term for the interaction of the all the living [biotic] and non-living [abiotic] factors in a specific environment

Answer 335

The range of different habitats from a small local habitat to the whole of the Earth.

Answer 336

A domain divided into four kingdoms: Protoctista; Fungi; Plantae and Animalia. Their cells possess membrane bound organelles; they have larger 80s ribosomes; membranes containing fatty acid chains attached to glycerol by ester linkages.

Answer 337

A coding sequence of bases.

Answer 338

Another name for a sex cell. A reproductive cell which carries only one copy of each chromosome. Female gametes are called the ova or eggs; the male gametes are called sperm.

Answer 339

A section of DNA that contains the coded information [i.e. a sequence of organic bases] to make a polypeptide or functional RNA.

Answer 340

Any change to one or more nucleotide bases, or a change in the sequence of bases in DNA. Gene mutations can occur during substitution of one base with another; insertion or deletion of one or more base pairs, causing a frame shift.

Answer 341

All the alleles of all the genes of all the individuals of the same species that occupy a particular space, at a particular time.

Answer 342

The total number of different alleles in a group of individuals of the same species that live in the same place and can interbreed

Answer 343

The complete set of genes in a cell, including those in mitochondria and/or chloroplasts

Answer 344

A place where a species lives, expressed in one or a few words e.g. pond, lake, river, coral reef, grassland; sand dune; deciduous woodland; heathland.

Answer 345

A single set of unpaired chromosomes in each nucleus. A cell that only contains one copy of each chromosome.

Answer 346

A class of basic proteins, with an unusually large proportion of the basic amino acids, arginine and lysine. Histones are associated with DNA in the chromosomes of eukaryotic cells.

Answer 347

Chromosomes which contain identical sets of gene loci. One chromosome in the pair has originated from the paternal sperm and the other from the maternal ovum/egg. Homologous chromosomes carry the same genes but not

Answer 348

The combination of genes of different varieties or species of organisms, to produce a hybrid.

Answer 349

The alleles of two or more different genes get shuffled into gametes independently of one another i.e. the allele a gamete inherits from one gene does not influence the allele received from a second gene [unless they are found close to each other on the same chromosome ]

Answer 350

Pairs of homologous chromosomes line up at random on the spindle apparatus during metaphase 1 of meiosis. The combination of chromosomes of maternal and paternal origin that go into the two daughter cells is a matter of chance

Answer 351

A multiple cropping practice where two or more different species of plants are grown in close proximity e.g. one crop is grown between the rows of another crop, often to increase yields; pest control; suppress weeds.

Answer 352

Differences that occur between members of different species

Answer 353

Differenced that occur between members of the same species.

Answer 354

Non coding sequences of bases made up of multiple repeats of base sequences.

Answer 355

The position and location of a particular gene [section of DNA].

Answer 356

Arithmetic mean. The sum of the sampled values divided by the number of items.

Answer 357

This is the central or middle value of a set of values. This requires arranging the values in ascending order,

Answer 358

A single polynucleotide chain, smaller than DNA but larger than tRNA. Helical in shape. Manufactured in the nucleus during transcription but found throughout the cell.

Answer 359

This is the single value of a sample that occurs most often.

Answer 360

A change in the genetic material in a cell. It may be a chromosome change or a change in the DNA nucleotide sequence of a gene.

Answer 361

The role of a species in an ecosystem. A niche includes a description of all a species' interactions with the different factors in its environment [i.e. its' address and its profession'.]

Answer 362

A process which occurs during anaphase 1 of meiosis. Individual homologous pairs of chromosomes fail to separate and usually results in a gamete having either one more or one less chromosome.

Answer 363

Reference to the genetic code. Each base in a sequence is read only once.

Answer 364

The evolutionary relationships between organisms. The evolutionary history of a particular taxon

Answer 365

Cans or jars buried in the ground, filled with paper or cardboard to provide shelter and covered with a lid or stone to keep out the rain. These are used to collect ground dwelling insects, which are often nocturnal.

Answer 366

Genes which individually have a very small effect on phenotype differences but collectively influence phenotypic characteristics that vary about a mean. Characteristics controlled by polygenes are more influenced by environmental effects than those determined by a single gene.

Answer 367

Having three or more complete sets of chromosomes. Polyploidy is common in plants but rare in animals. This is mainly because polyploid individuals are sterile when crossed with diploids. A polyploid suddenly arising in a diploid population can only reproduce asexually or by self- fertilisation.

Answer 368

Equipment used to suck up small invertebrate animals into a glass or plastic tube, when investigating local biodiversity.

Answer 369

Produced during transcription in eukaryotic cells. Pre mRNA contains sections called exons which code for proteins and non- coding sections called introns.

Answer 370

The full range of proteins produced by a specific cell type under a certain set of conditions.

Answer 371

A nucleic acid found in the nucleolus of eukaryotic cells and in the cytoplasm as ribosomes or attached to rough endoplasmic reticulum. Made from a single polynucleotide chain. Each nucleotide consists of a phosphate group, a pentose sugar ribose and one of four organic bases [adenine, guanine, uracil and cytosine]. RNA has a role in transcription and translation of DNA during protein synthesis.

Answer 372

An enzyme which joins RNA nucleotides together to form pre-mRNA, during transcription

Answer 373

A substitution of a base results in a different triplet to the original one but it codes for the same amino acid. This is because the genetic code is degenerate.

Answer 374

A group of organisms of common ancestry that interbreed to produce fertile offspring

Answer 375

The number of different species and the number of individuals of each species within one community

Answer 376

The number of different species and their abundance found in a particular area at a given time.

Answer 377

The number of different species found in a particular area at a given time.

Answer 378

The process which removes the intron non coding base sequences from pre-mRNA and the functional coding exons are joined together in the nucleus.

Answer 379

Type of selection that operates against the extremes of the range of phenotypes. This preserves the characteristics of a population so the population remains the same over time.

Answer 380

Used in statistics to measure the spread of the sample values from the mean. It is a better measure of spread than the range because standard deviation is less affected by extreme values.

Answer 381

Large net which is often used to catch flying insects or insects which live in long grass.

Answer 382

A group of organisms at any rank in the hierarchical classification scheme devised by Linnaeus e.g. any named species, genus, family order, class, phylum or kingdom.

Answer 383

The study and practice of naming and classifying species and groups of species within the hierarchical classification scheme.

Answer 384

The process of copying exactly the sequence of bases which code for a polypeptide in a section of DNA , into mRNA.

Answer 385

The process of copying the triplet code from a DNA template into a single strand of mRNA.

Answer 386

A single small polynucleotide chain folded into a clover shaped molecule, with one end extending beyond the other to enable attachment to an amino acid. The opposite end contains an anticodon loop with three bases forming an anticodon.

Answer 387

The process by which the base sequence in mRNA is used as a template to which complementary tRNA molecules attach and the amino acids they carry are linked together to form a polypeptide.

Answer 388

A sequence of three nitrogenous bases read along the DNA strand that code for amino acids.

Answer 389

A piece of equipment which is used to extract small invertebrates especially arthropods from soil or leaf litter.

Answer 390

With a few minor exceptions, each triplet of bases codes for the same amino acid in all organisms

Answer 391

A graph which displays the percentage absorbance of light at different wavelengths by chlorophyll pigments

Answer 392

Consist of chlorophyll b and carotenoids such as carotene and xanthophyll. Chlorophyll b absorbs light around 500- 640nm and reflects blue-green light. The carotenoids absorb blue light around 450-470nm and reflect yellow and orange light. Accessory pigments harvest light energy across a broad spectrum of wavelengths and transfer it to the primary pigment, chlorophyll a.

Answer 393

A graph which displays the rate of photosynthesis at different wavelengths of light.

Answer 394

A sequence of enzyme controlled chemical reactions which requires oxygen and produces carbon dioxide, water and much ATP.

Answer 395

Saprobiontic bacteria and fungi break down urea and proteins/nucleic acids in dead organisms to release ammonia, which then forms ammonium ions in the soil

Answer 396

A sequence of enzyme controlled chemical reactions which take place in the absence of oxygen and produces lactate [in animals] or ethanol and carbon dioxide [in plants and fungi]. Only a small quantity of ATP is formed in both cases.

Answer 397

Manufactured compounds usually containing the elements, nitrogen phosphorus and potassium. Manufactured from hydrocarbons or mined from rocks and their deposits, which are then blended together to give the appropriate balance of minerals for a particular crop.

Answer 398

A channel protein and enzyme which spans the thylakoid membranes or cristae of mitochondria. Hydrogen ions move through the channels within ATP synthase down an electrochemical gradient. The ATP synthase protein spins as the protons pass through and the active site accepts ADP and a phosphate ion to produce ATP, during chemiosmosis.

Answer 399

The total mass of living material in a specific area at a given period of time

Answer 400

A technique used to estimate the chemical energy store in dry mass . In bomb calorimetry, a sample of dry material is weighed and burnt in pure oxygen. The heat of combustion causes a small temperature rise in the surrounding water bath and then temperature rise can then be used to calculate the energy released from the burnt biomass.

Answer 401

The light independent stage of photosynthesis, located in the stroma of the chloroplast

Answer 402

The flow of protons [hydrogen ions] through ATP synthase channels, creating an electrochemical force that is enough to produce ATP. It occurs in the cristae of the mitochondria and in the thylakoid membranes of chloroplasts during photosynthesis. It also occurs in the cell surface membranes of prokaryotes.

Answer 403

The main pigment involved in photosynthesis. Chlorophyll a is the primary pigment found at the centre of photosystem I and photosystem II. Chlorophyll b is one of the accessory pigments. They are both involved in trapping visible light of certain wavelengths. Both reflect green light and do not absorb light of this wavelength.

Answer 404

A small organic non-protein molecule/cofactor. Coenzymes are involved in enzyme catalysed reactions by donating or accepting hydrogen ions between different enzyme catalysed reactions

Answer 405

This id often referred to as CoA. It carries the 2-carbon acetyl group made from pyruvate in the link reaction to the Krebs cycle. CoA also carries acetyl groups made from beta oxidation of fatty acids and some amino acids to the Krebs cycle.

Answer 406

The point where the rate of photosynthesis is equal to the rate of respiration. At this point there will be no net exchange of gases into or out of the plant.

Answer 407

The maintenance of biodiversity and sustainability of biological resources using different methods of in situ [e.g. protected areas of natural habitat] and ex situ management [zoos; seed banks].

Answer 408

A living organism that obtains its energy by feeding on other organisms. Primary consumers are herbivores; secondary and tertiary consumers are usually predators but they may also be scavengers or parasites.

Answer 409

The highly folded inner membranes of the mitochondria where the electron carriers and enzymes are found during oxidative phosphorylation

Answer 410

The formation of ATP using light energy but involving photosystem I. Electrons from photosystem I pass back to the chlorophyll molecule from which they were originally lost, after passing along electron carrier molecules. Photolysis of water does not occur and NADP is not reduced.

Answer 411

The removal of carbon dioxide from a substrate molecule in the link reaction and the Krebs cycle.

Answer 412

An enzyme involved in the removal of hydrogen atoms from a substrate molecule. Usually associated with a coenzyme.

Answer 413

The process in which nitrate ions [NO3- ]are reduced by anaerobic bacteria such as Pseudomonas to nitrogen gas [N2]

Answer 414

Organisms that ingest waste and decaying organic material and then excrete nutrients into the soil e.g. slugs; earthworms; millipedes, woodlice.

Answer 415

Percentage efficiency is equal to the energy available after the transfer divided by the energy available before the transfer, then multiplied by 100.

Answer 416

An evolutionary theory used to explain the evolution of mitochondria and chloroplasts. At some point in time, free living prokaryotes became incorporated in eukaryotic cells and over time developed as chloroplasts and mitochondria.

Answer 417

A metabolite formed during anaerobic respiration in plant and fungi cells. Pyruvate is decarboxylated by the enzyme pyruvate decarboxylase to form ethanal

Answer 418

A product of anaerobic respiration in plant and fungi cells. Ethanal accepts hydrogen atoms from reduced NAD by the enzyme ethanol dehydrogenase. Ethanal is reduced to ethanol and NAD is oxidised .

Answer 419

The excessive concentration of nutrients e.g. nitrate ions, in streams, rivers and lakes which cause algal blooms. Light becomes a limiting factor for the continued growth of plants at lower depths, which consequently die. Dissolved oxygen concentration then becomes a limiting factor in the water, so aerobic organisms die. Anaerobic organisms flourish and further decompose dead material releasing more nitrate ions and some toxic waste such as hydrogen sulphide, which make the water putrid.

Answer 420

Flavin adenine dinucleotide [FAD]. This acts as a hydrogen carrier and is tightly bound to a dehydrogenase enzyme embedded in the inner mitochondrial membrane. FAD does not pump hydrogen ions into the intermembrane space but instead, returns them to the matrix.

Answer 421

A food chain describes the feeding relationship and the transfer of energy between a producer and its associated consumers

Answer 422

A food web describes the feeding relationships and the transfer of energy between several food chains linked together as a consequence of most animals relying on multiple food sources.

Answer 423

A three carbon molecule commonly known as GP, formed following carboxylation of RUBP and CO2. The resulting 6C unstable molecule breaks down into two 3C molecules of GP in the Calvin cycle.

Answer 424

A sequence of chemical reactions where the six carbon glucose molecule is split into two 3-carbon molecules of pyruvate. This process is oxygen independent and occurs in the cell cytoplasm.

Answer 425

A stack of thylakoid membranes, containing chlorophyll pigments which absorb light energy during cyclic and non-cyclic photophosphorylation.

Answer 426

The total quantity of the chemical energy store in plant biomass in a given area, in a given time. Abbreviated to GPP.

Answer 427

Excretory product rich in phosphate ions formed from the waste material of some sea birds.

Answer 428

Habitat refers to the place or location where an organism [or a population of the same species] lives, resides or exists e.g. freshwater pond. grassland; desert

Answer 429

This occurs in the matrix of the mitochondria and is oxygen dependent. Acetyl coenzyme A is introduced into a cycle of oxidation-reduction reactions that yield some ATP and a large quantity of reduced NAD and FAD [which are used in oxidative phosphorylation]

Answer 430

A product of anaerobic respiration in muscle cells of animals. Pyruvate acts as a hydrogen acceptor from reduced NAD to form lactate. Lactate dehydrogenase catalyses the reduction of pyruvate to lactate and the oxidation of NAD.

Answer 431

The loss of water soluble nutrients from the soil. Rainwater dissolves soluble nutrients such as nitrate ions and this percolates down through the soil layers and enter watercourses such as streams, rivers and lakes.

Answer 432

Plants which belong to the family Leguminosae (Fabaceae) e.g. peas; beans; clover. Many of them have swollen root nodules containing nitrogen fixing bacteria such as Rhizobium. The bacteria obtain carbohydrates/ sugars from the plant and the plant acquires amino acids from the bacteria.

Answer 433

An environmental factor that limits the rate of a process. Any increase in such as factor, will allow a corresponding increase in the rate of the process. If there are a number of limiting factors, the rate is determined by the one which is at its lowest value [furthest away from its' optimum level].

Answer 434

This occurs in the matrix of the mitochondria where the 3-carbon pyruvate molecules enter a series of reactions which lead to the formation of a 2-carbon molecule called acetyl coenzyme A.

Answer 435

The interior solution in the mitochondria. It contains lipids, and enzymes involved in the Krebs cycle. Mitochondrial DNA and 70S ribosomes allow the production of some mitochondrial proteins

Answer 436

The cultivation of a single species of crop in a given area.

Answer 437

An association between organisms of two different species and both species benefit from the association. e.g. nitrogen fixing bacteria and leguminous plants. A type of symbiosis.

Answer 438

A mutualistic relationship between certain types of fungi and the roots of many plants where both gain benefit. The fungi help to extend the surface area of the root system of plants thereby increasing the absorption of mineral ions and water. The plants in return supply sugars to the fungi.

Answer 439

Nicotinamide adenine dinucleotide [NAD] is a coenzyme and a hydrogen carrier molecule. The nicotinamide part accepts a pair of hydrogen atoms and becomes reduced. It is oxidised when it loses the hydrogen atoms. NAD is an important molecule involved in all stages of respiration

Answer 440

A dehydrogenase enzyme that catalyses the oxidation of reduced NAD so that NAD can be recycled for reuse in the link reaction and the Krebs cycle.

Answer 441

Nicotinamide dinucleotide phosphate. A coenzyme and acceptor of electrons from the electron transport chain located in the thylakoid membranes and hydrogen ions, which pass out of the thylakoid space through ATP synthase. Reduced NADP is a product of non-cyclic photophosphorylation and is later oxidised during the Calvin Cycle

Answer 442

Consists of dead and decaying animal and plant remains as well as animal wastes such as manure, slurry and bone meal.

Answer 443

The chemical energy store in plant biomass which is left after losses to respiration have been considered. This is available for plant growth and reproduction. It is also available to other trophic levels such as herbivores and decomposers. Abbreviated to NPP.

Answer 444

The chemical energy store which is available and incorporated into new consumer biomass. It can be calculated as N = I - (F+R) where N = net production; I represents the chemical energy store of ingested food; F represents the energy lost in faeces and urine; R represents the energy lost in respiration. Primary and secondary productivity is measured as biomass in a given area in a given time e.g. kJ ha-1 year-1

Answer 445

The process in which ammonium ions are oxidised to nitrate ions by the bacteria Nitrosomonas and Nitrobacter, during the nitrogen cycle.

Answer 446

he process in which nitrogen gas is changed into ammonium ions by nitrogen fixing organisms such as Azotobacter, Rhizobium and some Cyanobacteria. Only some prokaryotes are able to do this

Answer 447

The Z Scheme'. The formation of ATP using light energy. Electrons flow from photosystem II to photosystem I, through a series of electron carriers. Reduced NADP is also formed. The electrons lost from photosystem II are replaced by those released by the photolysis of water.

Answer 448

A chemical reaction in which hydrogen atoms or electrons are lost or oxygen atoms are gained.

Answer 449

This takes place on the inner mitochondrial membranes. Electrons [associated with reduced NAD and FAD] flow along the electron transport chain, providing energy for the active transport of hydrogen ions. ADP is phosphorylated to ATP during chemiosmosis.

Answer 450

The oxidation of a chlorophyll molecule. The loss of two electrons from a chlorophyll molecule, when a chlorophyll molecule absorbs light energy.

Answer 451

The splitting of water molecules by the reaction centre of photosystem II.

Answer 452

A funnel shaped collection of accessory pigments with a reaction centre containing a complex of proteins and chlorophyll molecules at its base, embedded in the thylakoid membrane, the primary pigment is chlorophyll a

Answer 453

A funnel shaped collection of accessory pigments such as chlorophyll b, carotenes and xanthophylls. A primary reaction centre at the base consists of a form of chlorophyll a, P700, proteins and cofactors. P700 has a maximum absorption of light at 700 nm.

Answer 454

A funnel shaped collection of accessory pigments such as chlorophyll b, carotenes and xanthophylls. A primary reaction centre at the base consists of a form of chlorophyll a, P680, proteins and cofactors. P680 has a maximum absorption of light at 680 nm.

Answer 455

The protection of ecosystems, habitats and species for the future without allowing any use by humans.

Answer 456

They are photosynthetic organisms that manufacture complex organic substances from light energy and use simple inorganic molecules such as water, carbon dioxide and mineral ions

Answer 457

A three carbon molecule. A 6-carbon molecule of glucose is split into two 3- carbon molecules of pyruvate during glycolysis in the cell cytoplasm.

Answer 458

A chemical reaction in which hydrogen atoms or electrons are gained or oxygen atoms are lost.

Answer 459

This is the ratio of carbon dioxide produced by a respiring organism to the oxygen consumed in a given period of time. As it is a ratio, there are no units required. RQ values tell us what type of respiratory substrate is being metabolised and what type of respiration. RQ glucose = 1.0; RQ protein = 0.9; RQ triglycerides = 0.7; during anaerobic respiration, the RQ will be infinity.

Answer 460

A five carbon molecule involved in the fixation of atmospheric CO2 during the light independent stage of photosynthesis. RUBP combines with a molecule of carbon dioxide to form an unstable six carbon compound. This is catalysed by the enzyme RuBisCO. The unstable six-carbon molecule quickly splits into two 3-C molecules of glycerate phosphate. [GP'

Answer 461

The enzyme involved in fixing carbon dioxide, a process known as carboxylation. Rubisco combines carbon dioxide to a five carbon molecule called ribulose bisphosphate [RuBP] into an unstable six carbon compound which splits into two three carbon molecules of GP. Rubisco is correctly called ribulose bisphosphate carboxylase oxygenase, but commonly referred to as Rubisco.

Answer 462

A group of organisms [mainly bacteria and fungi] that break down complex materials in dead and decaying organisms into simple ones during extracellular digestion. Valuable minerals are released back into the soil, which can then be absorbed by plants.

Answer 463

The colourless thick fluid which surrounds the grana in the chloroplasts. The light independent stage or Calvin cycle takes place in the stroma. Starch grains and oil droplets are also present in the stroma.

Answer 464

Formation of ATP directly from ADP and Pi during glycolysis and the Krebs Cycle when one molecule is converted to another. It contrasts with ATP formed by oxidative phosphorylation.

Answer 465

A complex arrangement of internal membranes which are grouped into stacks called grana [singular: granum], joined by intergranal lamellae. Chlorophyll pigments which absorb light energy, are located on the thylakoid membranes.

Answer 466

GP molecules are reduced by the addition of hydrogen from reduced NADP [which now becomes re- oxidised]. ATP is converted to ADP during this step [phosphorylation] with the release of energy and phosphate. Two molecules of triose phosphate [TP] are formed during the Calvin cycle.

Answer 467

A stage in a food chain or food web. The arrows on the food chain diagram represent the direction of energy flow.

Answer 468

Anisotropic band. A dark region consisting of overlapping thin actin and thicker myosin filaments. The A band remains the same width when a myofibril contracts.

Answer 469

A plant growth factor that has a role in the closure of stomata in the leaves by guard cells. ABA also inhibits the production of amylase and this inhibits germination and prolongs seed dormancy. ABA promotes senescence and leaf abscission [leaf fall].

Answer 470

An enzyme which breaks down the neurotransmitter, acetylcholine, the products of which are absorbed back into the presynaptic knob.

Answer 471

A common neurotransmitter substance released at excitatory synapses. Acetylcholine is made up of two parts: acetyl [ethanoic acid] and cholinne

Answer 472

A thin type of protein filament found in a myofibril. Consists of two strands twisted around each other.

Answer 473

A form of potential energy resulting from behaviour of charged ions leading to their unequal distribution across a membrane. The inside of an axon is positively charged relative to the outside and is usually around +40mV in humans. Provided a stimulus reaches threshold level, voltage gated sodium channels start to open and sodium ions move into the axon down a concentration and electrochemical gradient. The influx of sodium ions raises the membrane potential from its resting level of -70mV but does not immediately start an impulse. If the stimulus raises the membrane potential to -55mV [threshold potential], this causes whole sale opening of the voltage gated sodium channels and further sodium ions flood into the neurone.

Answer 474

A small blood vessel which arises from a branch of the renal artery and supplies the nephron with blood. The afferent arteriole enters the renal capsule to form the glomerulus.

Answer 475

For any given neurone, the amplitude of the action potential is constant, as long as the stimulus reaches the threshold value. Increasing the strength or number of stimuli has no effect on the amplitude of an action potential.#

Answer 476

A description of structures or chemicals in the body which perform opposite actions to each other e.g. biceps and triceps muscles.

Answer 477

Produced in the hypothalamus and stored in the posterior pituitary gland. ADH increases the permeability of the distal convoluted tubule to water. ADH increases the permeability of the collecting duct to water and urea.

Answer 478

A carrier protein molecule that transports two substances across membranes in opposite directions.

Answer 479

Auxins produced at the apical/ shoot meristem not only cause the stem to grow upwards but they also inhibit the growth of lateral [side] buds. If the shoot tip/ apical meristem and the source of auxin is removed, lateral shoots start to grow and the plant becomes bushier in appearance.

Answer 480

Water channels that are inserted into the cell membrane when stimulated by ADH. They allow water molecules to pass across membranes

Answer 481

A group of cells which lie between the atria of the heart. After a short delay, the AVN conveys a wave of electrical excitation between the ventricles along Purkyne fibres.

Answer 482

Part of the nervous system that controls automatic responses such as heart rate; peristalsis in the gut. It consists of the sympathetic and parasympathetic nervous systems.

Answer 483

A long single fibre that carries nerve impulses away from the cell body of a neurone

Answer 484

A type of sensory receptor which detects blood pressure.

Answer 485

The energy used by the body at rest to sustain its vital organs.

Answer 486

A collection of Purkyne fibres located in the inner ventricular walls, which convey a wave of electrical excitation from the AVN to the apex of the ventricles.

Answer 487

Found exclusively in the heart. Myogenic. Cardiac muscle cells appear striated under the microscope with many mitochondria. Cardiac muscle cells are connected by intercalated discs.

Answer 488

Main arteries which supply blood from the heart to the head. Chemoreceptors located in the walls of the carotid arteries are sensitive to the pH of the blood resulting from changes in blood carbon dioxide concentration.

Answer 489

The release of a substance by one cell which transmits information to another cell, either locally or over some distance

Answer 490

A division of the nervous system consisting of the brain and the spinal cord.

Answer 491

A type of receptor which responds to chemicals e.g. blood carbon dioxide concentration.

Answer 492

Synapses which release acetylcholine as a transmitter substance. Cholinergic synapses are common in vertebrates where they occur in the CNS and at neuromuscular junctions.

Answer 493

Several distal convoluted tubules from nephrons drain into a collecting duct in the medulla. It is lined with cuboidal epithelial cells without a brush border. The collecting duct widens as it empties into the pelvis.

Answer 494

A light receptor cell found in the retina of the mammalian eye, which acts as a transducer. Cone cells are fewer in number than rod cells and are concentrated at the fovea. There are three types of cone cells, each type responds to a specific range of wavelengths of light to produce images in full colour. Each cone cell has its own connection to a single bipolar neurone and gives high visual acuity.

Answer 495

The lighter coloured outer region of the kidney made up of renal [Bowman's] capsules, convoluted tubules and blood vessels.

Answer 496

Cyclic AMP acts as a second messenger in signal conduction within cells. Cyclic AMP is involved in glycogen, lipid and sugar metabolism.

Answer 497

The release of a substance by one cell which transmits information to another cell, either locally or over some distance.

Answer 498

A division of the nervous system consisting of the brain and the spinal cord.

Answer 499

A type of receptor which responds to chemicals e.g. blood carbon dioxide concentration.

Answer 500

Synapses which release acetylcholine as a transmitter substance. Cholinergic synapses are common in vertebrates where they occur in the CNS and at neuromuscular junctions.

Answer 501

Several distal convoluted tubules from nephrons drain into a collecting duct in the medulla. It is lined with cuboidal epithelial cells without a brush border. The collecting duct widens as it empties into the pelvis.

Answer 502

A light receptor cell found in the retina of the mammalian eye, which acts as a transducer. Cone cells are fewer in number than rod cells and are concentrated at the fovea. There are three types of cone cells, each type responds to a specific range of wavelengths of light to produce images in full colour. Each cone cell has its own connection to a single bipolar neurone and gives high visual acuity.

Answer 503

The lighter coloured outer region of the kidney made up of renal [Bowman's] capsules, convoluted tubules and blood vessels

Answer 504

Cyclic AMP acts as a second messenger in signal conduction within cells. Cyclic AMP is involved in glycogen, lipid and sugar metabolism.

Answer 505

An extension of the cell body of a neurone, which can subdivide into smaller branches called dendrites. Dendrons carry nerve impulses towards the cell body of a neurone.

Answer 506

The state of part of an axon when the inside of the membrane is more positively charged [+40mV] in comparison to the tissue fluid outside. When an action potential occurs.

Answer 507

A chronic condition that results in high concentrations of blood glucose. It is caused by the failure of the pancreas to produce insulin or by the body cells becoming insensitive to the hormone. Type 1 diabetes [insulin dependent diabetes] commonly diagnosed during childhood or early adulthood. Type 2 diabetes [non-insulin dependent] occurs in middle age and usually results from an insensitivity of cells to insulin although there may be a deficiency in insulin production. Type 2 diabetes is commonly treated by a low sugar diet and tablets.

Answer 508

A series of coiled/ folded parts of the nephron, surrounded by blood capillaries and located in the kidney cortex. Sometimes called the second convoluted tubule. Its walls are made of cuboidal epithelial cells but they are not as wide as the cells of the PCT. The cells of the DCT have no brush border

Answer 509

An animal that does not have physiological mechanism to maintain a constant core body temperature. These animals rely on behavioural adaptations to ensure that their core temperature does not sink too low or rise too high e.g. reptiles.

Answer 510

An organ that becomes active in response to a nerve impulse e.g. muscle; gland.

Answer 511

A tiny blood vessel that leaves the renal capsule . It has a smaller diameter than the afferent renal arteriole, resulting in a hydrostatic pressure within the glomerulus. The efferent arteriole carries blood away from the renal capsule and later branches to form the vasa recta [dense network of capillaries] which surround the proximal convoluted tubule, the Loop of Henle and the distal convoluted tubule.

Answer 512

A gland that secretes its product [hormone] directly into the bloodstream, rather than via a duct.

Answer 513

A series of ductless glands which produce and secrete chemical messengers called hormones into the blood stream which affect target organs. Hormonal responses are generally slower than those initiated by electrical impulses carried by neurones but hormones control long lasting effects such as growth, metabolic rate and the oestrous cycle

Answer 514

An animal that maintains its body temperature using heat generated within its body tissues e.g. mammals and birds.

Answer 515

Muscle in the skin which when contracted ,raises hairs on mammalian skin. When relaxed, hairs are lowered.

Answer 516

A plant growth factor which stimulates fruit ripening. This can be useful in fruits that are delicate and liable to damage in transit e.g. bananas. The fruit can be picked hard and unripe, transported and then artificially ripened with ethene, at their destination.

Answer 517

The removal from the body of metabolic waste substances e.g. urea, carbon dioxide; bile pigments and other substances in excess such as water and ions.

Answer 518

These type of muscle fibres contract rapidly, fatigue rapidly and produce powerful contractions over a short period of time. They are adapted for intense exercise e.g. weight lifting. They possess thicker and more numerous myosin filaments; a high concentration of glycogen; high concentrations of enzymes involved in anaerobic respiration to provide ATP quickly; a store of phosphocreatine.

Answer 519

When pressure distorts the lamellae of a Pacinian corpuscle, stretch mediated sodium channels widen in the plasma membrane of the exposed axon of the sensory neurone at the centre of the Pacinian corpuscle. Sodium ions diffuse into the neurone and the membrane becomes depolarised to produce a generator potential

Answer 520

A group of plant growth factors produced in young leaves, seeds and root tips. Their functions include the stimulation of germination, flowering and increasing internode length leading to stem elongation. Like auxins, gibberellins stimulate cell elongation but also promote cell division.

Answer 521

The fluid formed in the renal capsule during ultrafiltration from the glomerulus. Fluid containing water, glucose, amino acids and mineral ions

Answer 522

A tightly arranged group of capillaries which sit inside a renal [Bowman's] capsule. Cells with prominent nuclei and branching extensions, called podocytes, suspend the glomerular capillaries within the Bowman's capsule

Answer 523

A peptide hormone which is produced by the larger alpha cells in the islets of Langerhans in the pancreas. Glucagon promotes the conversion of glycogen to glucose and also the formation of glucose from non-carbohydrate sources such as amino acids and glycerol.

Answer 524

The conversion of other substances such as lactate, amino acids, glycerol and fatty acids to glucose.

Answer 525

The conversion of glucose to glycogen in the liver.

Answer 526

The breakdown of glycogen to glucose in liver cells.

Answer 527

A plant growth response to gravity. Shoots show negative geotropism whilst roots are positively geotropic. This ensures that when a seed germinates the shoots and roots grow in the right direction, whatever the orientation of the seed. As roots are positively geotropic, this promotes anchorage in the soil and effective uptake of water and mineral ions.

Answer 528

A lighter region which occurs in the centre of the darker A band of a myofibril. The H zone consists only of myosin filament. The H zone becomes narrower during contraction of the myofibril.

Answer 529

The maintenance of a constant internal environment within restricted limits in organisms e.g. blood pH; blood glucose concentration; core temperature; water potential.

Answer 530

Occurs when potassium ions continue to exit the axon through voltage gated potassium channels. The voltage gated potassium channels do not close until the potential difference reaches - 80mV. This is lower than the normal resting potential.

Answer 531

A region of the brain which is involved in the monitoring and control of thermoregulation, osmoregulation and the release of certain hormones from the pituitary gland e.g. ADH; and the thyroid gland e.g. thyroxine.

Answer 532

Isotropic band. A light region consisting of thin actin filaments within a sarcomere. The I band becomes narrower when a myofibril contracts.

Answer 533

A plant growth substance which belongs to a group of substances called auxins. Auxins may 'switch' some genes on and others off. IAA is produced in the shoot tip and passes down to the zone of cell expansion, where it stimulates young cells to expand. Here it stimulates proteins called expansins, which make cell walls more flexible by loosening the hydrogen bonds between cellulose fibres.

Answer 534

A peptide hormone which is produced by the small beta cells in the islets of Langerhans in the pancreas. Insulin increases the permeability of muscle and liver cells to glucose. Insulin also activates enzymes that convert glucose into glycogen [glycogenesis]. Insulin increases the rate of respiration in muscle cells and the conversion of glucose into proteins and lipids.

Answer 535

Endocrine cells scattered between acini of the pancreas. Islets of Langerhans consist of larger but less numerous alpha cells with prominent nuclei, located generally at the periphery and smaller beta cells. Alpha cells secrete glucagon; beta cells secrete insulin.

Answer 536

A response to a stimulus which involves a change in speed of an organism and the rate at which it changes direction.

Answer 537

A long hair pin loop that extends from the cortex into the medulla of the kidney and back again. The descending limb is narrower in cross section and consists of squamous epithelium. The ascending limb has a wider cross section with cuboidal epithelial cells with no brush border but many mitochondria. The loop of Henle is surrounded by vasa recta blood capillaries.

Answer 538

The darker coloured inner region of the kidney, made up from loops of Henle, collecting ducts and blood vessels.

Answer 539

A region of the brain and part of the autonomic nervous system. It contains control centres for heart rate; breathing rate and blood flow rate.

Answer 540

This type of nerve cell carries nerve impulses from the central nervous system to effectors Cell body is at one end of the cell and has dendrites.

Answer 541

This forms a covering around the axon and is made up of the membranes of the Schwann cells. These membranes are rich is lipid and protein known as myelin. Myelin has electrical insulating properties. Neurones with a myelin sheath are called myelinated neurones.

Answer 542

Skeletal muscle consists of muscle fibres bundled together. Each muscle fibre contains many myofibrils, which are the contractile elements of the muscle. Each myofibril is made up of two types of protein filament: thin actin and thick myosin.

Answer 543

A pigment found in muscles which acts as an emergency store of oxygen for aerobic respiration. Myoglobin has a high affinity for oxygen and will only release oxygen when the surrounding concentration [partial pressure] of oxygen is very low.

Answer 544

A thick type of protein filament found in a myofibril. A molecule of myosin consists of a long rod shaped region with a bulbous head.

Answer 545

Type of control mechanism in which a change from the normal value of a physiological factor is detected and a response is made that restores the value to the norm. e.g. control of blood glucose level

Answer 546

The functional unit of the kidney that filters blood, reabsorbs useful substances and forms urine. Each nephron consists of a glomerulus and a tubule and is associated with many blood capillaries.

Answer 547

A specialised synapse where the end of a motor neurone meets a skeletal muscle fibre. Unlike nerve synapses, the postsynaptic membrane at a neuromuscular junction is folded to increase the surface area to allow more postsynaptic receptors to be present. In a neuromuscular junction a single impulse will always cause a contraction, unlike a nerve synapse.

Answer 548

A chemical substance released in small amounts by the ending of a nerve fibre; either at a synapse when it excites the adjacent nerve cell or at a motor nerve ending when it excites the adjacent effector organ. Acetylcholine, adrenaline and noradrenaline are common neurotransmitters.

Answer 549

A constriction between adjacent Schwann cells where there is no myelin sheath. The constriction is between 2- 3μm long and occurs every 1-3mm in humans. Nodes of Ranvier play a key role in saltatory conduction of nerve impulses.

Answer 550

A type of sensory receptor which detects concentration of body fluids.

Answer 551

The control of the water potential of the blood. This depends on the concentration of solutes such as glucose, proteins, sodium chloride and other mineral ions as well as the volume of water in the blood, tissue fluid and intracellular fluid.

Answer 552

A type of receptor which responds to mechanical stimuli such as pressure. Pacinian corpuscles occur deep in the skin and are most abundant on the fingers, soles of the feet and external genitalia. They also occur in joints, ligaments and tendons.

Answer 553

Part of the autonomic [involuntary/subconscious] nervous system which carries nerve impulses to glands, smooth muscle and cardiac muscle. Parasympathetic nervous system deals with the 'rest and digest' system.

Answer 554

The production of seedless fruits without fertilisation e.g. grapes. Auxins and gibberellins can be used to treat unpollinated flowers, causing them the develop seedless fruit

Answer 555

A division of the nervous system consisting of pairs of nerves running to and from the CNS.

Answer 556

Sometimes referred to a creatine phosphate. Phosphocreatine is a chemical stored in muscle fibres which acts as a reserve supply of phosphate to convert ADP to ATP. No lactate is produced in this process so it does not lead to muscle fatigue. Phosphocreatine stores in muscle fibres are limited and will run out in a few seconds. The system provides only enough extra ATP for short bursts of activity. The phosphocreatine store is replenished using phosphate from ATP when the muscle is relaxed.

Answer 557

The response of shoots to unilateral light. A young shoot will grow towards the light. This is known as positive phototropism.

Answer 558

Hormone like substances produced in response to external stimuli. Produced in small quantities. Unlike animal hormones, plant growth factors are not produced in specific organs although they may be produced in a restricted plant region. They are produced by unspecialised cells and their effects on the plant may vary in different circumstances. Responses include tropisms; stomatal closure; seed germination; fruit formation and ripening.

Answer 559

Cells in the inner layer of the Bowman's capsule of the nephron which wrap around the capillaries of the glomerulus. Podocytes form part of the ultrafiltration barrier along with the endothelium of the glomerular capillaries

Answer 560

The state of the axon when the inside of the membrane is more negatively charged [-70mV] in comparison to the tissue fluid outside.

Answer 561

The neurone which has receptors for the neurotransmitter substance on its membrane and possesses voltage gated sodium channels.

Answer 562

The neurone at a synapse which releases the neurotransmitter substance e.g. acetylcholine. The membrane of the presynaptic neurone has voltage gated calcium channels.

Answer 563

A series of coiled/ folded parts of the nephron, surrounded by blood capillaries and located in the kidney cortex. Sometimes called the first convoluted tubule. Its walls are made of epithelial cells which have many mitochondria and microvilli.

Answer 564

A series of specialised muscle fibres located in the inner ventricular walls [septum] which collectively make up the bundle of His. The bundle of His conducts the wave of excitation from the AVN, through the atrioventricular septum to the base of the ventricles. The ventricles then contract quickly from the apex upwards.

Answer 565

A sensory cell that can detect a stimulus. Receptors are specific to one type of stimulus. Photoreceptors detect light; chemoreceptors detect chemicals; proprioceptors detect body position; mechanoreceptors detect mechanical strain or stretching; baroreceptors detect blood pressure; osmoreceptors detect concentration of body fluids.

Answer 566

A rapid involuntary response to a sensory stimulus which usually has some protective or survival value. e.g. blinking; pupil reflex; withdrawal reflex; knee jerk.

Answer 567

The pathway of neurones involved in a reflex

Answer 568

A span of time [approx. 1ms] during which a second stimulus is unable to cause an impulse and which results from hyperpolarisation of the axon membrane. [absolute refractory period] . Relative refractory period follows, lasting for 5-10ms, during which a high intensity stimulus may produce a depolarisation.

Answer 569

Sometimes referred to as interneurons. Relay neurones are nerve cells with short axons that transmit electrical impulses from one neurone to another in the CNS

Answer 570

The closed end at the start of the nephron, located in the cortex. It is cup shaped and surround the glomerulus. The inner layer of the renal capsule is made up of podocytes

Answer 571

A funnel shaped cavity that collects urine into the ureter from the collecting ducts of the nephrons.

Answer 572

The resting potential of -70mV is re- established across a section of the axon membrane. Voltage gated sodium channels close and voltage gated potassium channels open and potassium ions move out of the axon due to electrochemical and concentration gradients.

Answer 573

A form of potential energy resulting from behaviour of charged ions leading to their unequal distribution across a membrane. The inside of an axon is negatively charged relative to the outside and is usually around -70mV in humans. The sodium-potassium pump actively transports three sodium ions out of the axon into tissue fluid for every two potassium ions pumped in. Membrane bound sodium voltage gated channels are closed which prevent sodium ions diffusing down a concentration gradient, back into the axon. Membrane bound potassium channels are also closed but they are leaky so potassium ions tend to diffuse out of the axon into tissue fluid. Consequently, there are more positive ions on the outside of the membrane than inside.

Answer 574

A light receptor cell found in the retina of the mammalian eye, which acts as a transducer. Rod cells are more numerous than cone cells and are sensitive to low intensity light, leading to images in black and white. Many rod cells link to a single bipolar cell and therefore give low visual acuity.

Answer 575

In a myelinated axon, depolarisation is largely prevented in the part of the axon covered by myelin. Action potentials occur at the nodes of Ranvier which then appear to 'jump from node to node'. This increases the speed of conduction.

Answer 576

The membrane which surrounds a muscle fibre.

Answer 577

The section of a myofibril between two Z lines.

Answer 578

The cytoplasm of a muscle fibre. The sarcoplasm contains a large concentration of mitochondria and endoplasmic reticulum.

Answer 579

A membrane bound structure found within a muscle fibres, similar to the endoplasmic reticulum in other cells. The main function of the sarcoplasmic reticulum is to store calcium ions.

Answer 580

These cells produce the myelin sheath, which wrap around the axon of a neurone. Schwann cells provide electrical insulation around the axon of a neurone. They also carry out phagocytosis [removal of cell debris] and play a part in nerve regeneration.

Answer 581

This type of nerve cell carries nerve impulses [electrical signals] from receptors towards the central nervous system. The cell body is not at the end of the cell and does not have dendrites.

Answer 582

A blood vessel which directly links an artery to a vein. In thermoregulation, shunt vessels can control blood flow by constriction or dilation. When dilated, shunt vessels divert blood away from the capillaries close to the skin surface thereby reducing heat loss.

Answer 583

Referred to as the 'pacemaker' of the heart. A distinct group of cells in the wall of the right atrium of the heart. The initial stimulus for contraction originates here. The SAN controls and coordinates the contraction of the heart.

Answer 584

A theory to explain how the thin actin and thick myosin filaments can slide past one another to shorten the myofibrils during muscle contraction.

Answer 585

These type of muscle fibres contract less rapidly and fatigue slowly. They provide less powerful contractions but over a long period of time. These type of muscle fibres are adapted to endurance work. They possess a large store of myoglobin, a rich blood supply and numerous mitochondria to produce ATP.

Answer 586

Non striated or involuntary muscle. Not under conscious control. Found in the walls of blood vessels, the gut, the iris of the eye.

Answer 587

Occurs when a number of different presynaptic neurones collectively release sufficient neurotransmitter to exceed the threshold level to trigger an action potential in the postsynaptic neurone.

Answer 588

A detectable change in the internal or external environment of an organism that leads to a response.

Answer 589

A special type of sodium channel in the plasma membrane of the sensory neurone ending at the centre of the Pacinian corpuscle.

Answer 590

Skeletal or voluntary muscle. Makes up the bulk of body muscle in vertebrates. Attached to bones by tendons. Under conscious control.

Answer 591

Part of the autonomic [involuntary/subconscious] nervous system which carries nerve impulses to glands, smooth muscle and cardiac muscle. Sympathetic nervous system deals with 'flight or fight' responses

Answer 592

A carrier protein molecule that transports two or more substances across a membrane in the same direction.

Answer 593

A junction between two nerve cells, consisting of a minute gap across which impulses pass either by an electrical current [electrical synapse] or more often by diffusion of a chemical neurotransmitter [chemical synapse]

Answer 594

A small gap between the presynaptic knob and the post synaptic membrane.

Answer 595

A simple response whose direction is determined by the direction of the stimulus. Taxes are classified as positive [movement towards the stimulus] or negative

Answer 596

Occurs when a single presynaptic neurone is activated several times in quick succession. The neurotransmitter released builds up in concentration to exceed the threshold value. An action potential is triggered in the postsynaptic neurone.

Answer 597

The value of approximately -55mV across the axon membrane which causes the opening of a large number of voltage gated sodium channels.

Answer 598

Something that changes one form of energy into another. A Pacinian corpuscle will change mechanical energy of the stimulus into an electrical impulse known as a generator potential.

Answer 599

Extensions of the sarcolemma which traverse [run across ] each muscle fibre and between myofibrils. They are involved in the uptake and release of calcium ions in the sarcoplasm, which in turn controls ATPase activity.

Answer 600

A growth response in a plant to a directional stimulus e.g. phototropism is a response to light; gravitropism [geotropism] a response to gravity; hydrotropism a response to moisture; thigmotropism a response to touch.

Answer 601

A protein which forms a fibrous strand wrapped around an actin filament.

Answer 602

A globular protein which binds to tropomyosin and can reversibly attach to calcium ions.

Answer 603

Pressure filtration resulting from the narrowing of the efferent renal arteriole in comparison to the afferent renal arteriole. Water, glucose, urea, amino acids, mineral salts pass from the blood into the Bowman's capsule. Large blood proteins and blood cells remain in the blood plasma.

Answer 604

A tube or duct arising from the pelvis region of the kidney which carries urine from the kidney to the bladder.

Answer 605

The diameter of the arterioles near the surface of the skin become narrower. This reduces the volume of blood reaching the skin surface through the capillaries. Most of the blood entering the skin, passes beneath the insulating layer of fat and so little heat is lost to the environment.

Answer 606

The diameter of the arterioles near the surface of the skin become larger. This allows warm blood to pass close to the skin surface through the capillaries. Heat from this blood is then radiated away from the body surface.

Answer 607

The ability to detect fine details or small distances with the eye.

Answer 608

Channel protein in the membrane whose opening is controlled by voltage

Answer 609

A dark line which traverses the middle of each I band. The section of the myofibril between two Z lines is known as a sarcomere.

Answer 610

Any physical or chemical factor that influences populations in a community. Examples include temperature; wind speed; light intensity; water availability and humidity

Answer 611

The adaptation [via genetic mutation] of an organism, which enables it to successfully spread into other environments. Adaptive radiation leads to speciation

Answer 612

One of the alternative or different forms of the same gene e.g. in pea plants there is a gene for the colour of the seed pod. This gene has two different alleles, an allele which codes for green pods and another allele which codes for yellow pods.

Answer 613

The number of times an allele occurs within the gene pool.

Answer 614

Speciation by any geographical mechanism that separates a population into physically distinct and separate sub groups which then become isolated from each other.

Answer 615

When two or more genes are located on the same chromosome, other than a sex chromosome.

Answer 616

Any chromosome which is not a sex chromosome

Answer 617

A large white sheet is placed on the ground or supported by struts and held below a tree. The tree is shaken to dislodge the animals. Very small animals can be collected from the beating tray with a pooter.

Answer 618

Any factor that influences populations in a community that is the result of the activities of organisms; examples include competition; predation; mutualism; disease; allelopathy.

Answer 619

The maximum population size of a species that a particular habitat can support over time

Answer 620

A statistical test used to test categoric data to see if there are differences between expected and observed data.

Answer 621

The point where non sister chromatids in a homologous pair of chromosomes [bivalent] cross over [and join] during prophase 1 of meiosis.

Answer 622

One copy of a duplicated chromosome generally joined to the other copy by a single centromere. Chromatids of a single chromosome occur after DNA replication during the S phase of interphase.

Answer 623

The community that is the final stage of a natural succession, which remains more or less stable over a long period of time e.g. deciduous oak woodland

Answer 624

When two alleles of the same gene influence the phenotype of a heterozygous organism because both are dominant over any other alleles of the gene, but neither allele is dominant over the other e.g. inheritance of human ABO blood groups.

Answer 625

An ecological term for a group of populations of two or more species which occupy the same geographical area at the same time.

Answer 626

The maintenance of biodiversity and sustainability of biological resources using different methods of in situ and ex situ management.

Answer 627

Features or characteristics which can be measured or observed across a complete range from one extreme to the other. There are many intermediate phenotypes between the two extremes. The data collected is quantitative. Characteristics are often controlled by many pair of alleles situated at different loci on different chromosomes. The influence of the environment is large on this type of variation e.g. height in humans; milk yield in cattle.

Answer 628

A succession that does not progress to the natural climax community. Factors that can cause this are grazing, mowing and fire.

Answer 629

The number of classes or categories minus one e.g. if humans can have blood group A, B, AB or O, there are four categories but three degrees of freedom

Answer 630

The inheritance of two characteristics, determined by two different genes located on different chromosomes

Answer 631

Containing two sets of chromosomes e.g. human somatic cells produced by mitosis.

Answer 632

Type of selection that favours one extreme of the range of phenotypes so the population changes over time. This type of selection pressure favours a combination of alleles that results in the mean moving to either the left or the right of its original position. e.g. antibiotic resistance in bacteria.

Answer 633

Features or characteristics which cannot be measured or observed across a complete range so they form distinct classes or categories using discrete or categoric data. Characteristics are often controlled by one pair of alleles. The influence of the environment is small on this type of variation e.g. ABO blood groups; ability to tongue roll

Answer 634

The least common form of selection but the most important in bringing about evolutionary change. This type of selection favours the extremes of the range of phenotypes at the expense of the intermediate phenotypes e.g. coho salmon. Large and small males each have a different competitive advantage over the intermediate sized males.

Answer 635

An allele that is always expressed in the phenotype, even when a different allele is also present.

Answer 636

An ecological term for the interaction of the all the living [biotic] and non-living [abiotic] factors in a specific environment.

Answer 637

Any abiotic factor of the soil. Examples include soil structure; salinity; temperature; oxygen content. These can all influence the composition of soil microbes and the distribution/abundance of plants and animals.

Answer 638

When genes interact in the expression of a characteristic. One gene supresses the expression of another gene

Answer 639

Often referred as the F1 generation. The first set of offspring produced by the parent generation.

Answer 640

When a small population colonises a new area, any population descending from this small 'ancestor' group will have a much reduced genetic diversity and a different allele frequency from other similar populations.

Answer 641

This is the likelihood of a particular species occurring in a quadrat. If a species occurs in 10 quadrats out of a total of 40, the frequency of its occurrence is 25%

Answer 642

A length of DNA or a sequence of nucleotide bases, that codes for a specific polypeptide and therefore a specific characteristic.

Answer 643

All the alleles of all the genes of all the individuals in a population at a given time.

Answer 644

A sharp reduction in population size due to environmental events such as earthquake, flood, fire, drought, disease or human activity. Any subsequent population increase is based on the limited gene pool available from the surviving individuals.

Answer 645

A change in allele frequency in the absence of natural selection.

Answer 646

The alleles present in the cells of an individual organism which code for a particular characteristic. It is also used to refer to the entire complement of alleles that an organism has.

Answer 647

A place where a species lives, expressed in one or a few words e.g. pond, lake, river, coral reef, grassland; sand dune; deciduous woodland; heathland.

Answer 648

Containing one set of chromosomes e.g. gametes produced during meiosis.

Answer 649

A mathematical equation that can be used to calculate the allele frequencies of a particular gene in a population. The principle assumes that the proportion of dominant and recessive alleles of any gene in a population remains constant from one generation to the next. p+q = 1, where p = the frequency of the dominant allele; q = frequency of the recessive allele. In a single population, the genotype frequency can be represented as p2 + 2pq + q2 = 1, where p2 = the frequency of the homozygous dominant genotype; 2pq = the frequency of the heterozygous dominant and q2 = the frequency of the homozygous recessive genotype.

Answer 650

The state of having two different alleles for a specific gene in a diploid cell.

Answer 651

Pairs of chromosomes in a diploid cell. Each chromosome within the pair, carry the same sequence of genes occupying the same loci along their length, but not necessarily the same alleles.

Answer 652

The state of having two identical alleles for a specific gene in a diploid cell.

Answer 653

When neither of two alleles of a gene dominates so there is blending of the two alleles to form an intermediate e.g. if two alleles for petal colour in flowers were red and white, all heterozygotes would be pink

Answer 654

Individuals of different species complete with one another for resources such as light, food, water, breeding sites, mates.

Answer 655

The range of differences in characteristics of organisms across different species.

Answer 656

Individuals of the same species complete with one another for resources such as light, food, water, breeding sites, mates.

Answer 657

The range of differences in characteristics of organisms within a species

Answer 658

The position of a gene on a particular DNA molecule.

Answer 659

A method of estimating abundance of motile animal species, which is based on various assumptions. Marked individuals have the same probability of being recaptured as unmarked individuals; the mark must not rub off or wash off; the mark must not harm the individual or make it more susceptible to predation; there must be no immigration into or emigration out from the population; there are no deaths or births within the population between the mark and recapture times.

Answer 660

The inheritance of a single gene which controls a specific characteristic e.g. wing length in the fruit fly, Drosophila

Answer 661

A gene has more than two types of alleles. However, as there are only two chromosomes in a homologous pair, only two of the three or more different alleles can be inherited e.g. human ABO blood groups where there are three different alleles IA; IB; IO

Answer 662

The mechanism for evolution. It is the survival to reproductive age of those organisms with characteristics best suited to their environment. This increases the chances of their alleles being passed on to subsequent generations.

Answer 663

The role of a species in an ecosystem. A niche includes a description of all a species' interactions with the different factors in its environment

Answer 664

An estimate of the area within a quadrat that a particular plant species occupies. The technique is useful where a species is particularly abundant or difficult to count.

Answer 665

The observable characteristics of an organism, which may be visual or biochemical. The environment can alter an organism's phenotype.

Answer 666

The first organisms in the process of succession to colonise an inhospitable environment. Pioneer species often reproduce asexually, produce large quantities of wind dispersed seeds or spores; germinate rapidly; can photosynthesise, fix nitrogen from the atmosphere and are tolerant of extreme conditions.

Answer 667

Cans or jars buried in the ground, filled with paper or cardboard to provide shelter and covered with a lid or stone to keep out the rain. These are used to collect ground dwelling insects, which are often nocturnal

Answer 668

Equipment used to suck up small invertebrate animals into a glass or plastic tube, when investigating local biodiversity.

Answer 669

All the members of the same species living in a particular area at the same time. In species which reproduce sexually, there is interbreeding between males and females to produce fertile offspring.

Answer 670

An organism that feeds on another organism

Answer 671

An organism that is eaten by another organism

Answer 672

The colonisation of land that has never been colonised before, followed by the progression of changes in the abiotic environment, until a climax community is established. Primary succession leads to a greater number of habitats and niches and increased biodiversity.

Answer 673

A group of organisms that always produce offspring with the same phenotype and genotype e.g. TT x TT; tt x tt

Answer 674

A square wooden or metal frame [of varying dimensions] used in ecology, to isolate a standard unit area to study the distribution and abundance of very slow moving and sessile organisms

Answer 675

The random organisation of homologous chromosomes on the spindle equator during metaphase 1 of meiosis. This also occurs with the chromatids during metaphase II of meiosis

Answer 676

The random separation of homologous chromosomes during anaphase 1 and chromatids during anaphase II of meiosis

Answer 677

An allele that is only expressed in the phenotype if it is present in the homozygous state

Answer 678

A factor that gives a greater chance of survival to some members of the population than others

Answer 679

One of the communities during a succession e.g. pioneer community; grasses, scrubland.

Answer 680

A chromosome involved in determining the sex of an organism. In humans, there are X and Y chromosomes; females have two X chromosomes; males have one X and one Y chromosome.

Answer 681

Refers to genes carried on the X chromosome e.g. haemophilia.

Answer 682

The evolution of new species from existing ones. A species is a group of individuals that have a common ancestry and so share the same genes but different alleles and are capable of breeding with one another to produce fertile offspring. Members of a species are reproductively separated from other species.

Answer 683

The type of selection that operates against the extremes of a range of phenotypes, so the population remains the same over time e.g. body mass of human children at birth.

Answer 684

A statistical test used to find out whether the means of two sets of data are significantly different. To use the t-test, both sets of data must show a normal distribution

Answer 685

The slow change in communities that occurs when new land becomes available to colonise [primary succession] or when vegetation is cleared [secondary succession]

Answer 686

Large net which is often used to catch flying insects or insects which live in long grass.

Answer 687

Speciation by reproductive differences that cause members of a population to become isolated while living in close proximity.

Answer 688

This is used in ecology when the study area includes an environmental gradient or transition in the plant and animal communities e.g. rocky shore. A line or belt transect is used to sample along the environmental gradient.

Answer 689

A genetic cross carried out with a double recessive phenotype/genotype to distinguish homozygous dominant and heterozygous dominant genotypes for a particular characteristic.

Answer 690

A piece of equipment which is used to extract small invertebrates especially arthropods from soil or leaf litter.

Answer 691

A range of differences in characteristics between organisms.

Answer 692

The phenotype of the standard form of a species as it exists in nature. The wild type is considered to be the 'normal' allele at a locus, in contrast to that produced by a 'non- standard' mutant allele.

Answer 693

A process where acetyl groups are transferred from acetyl coenzyme A to the histones surrounding DNA. Increased acetylation decreases the positive charge on histones and decreases their attraction to the phosphate groups on DNA. The DNA-histone complex becomes less condensed and the DNA is more accessible to transcription factors which then can initiate mRNA production. The gene is switched on.

Answer 694

The process where primers join to their complementary bases at the end of the DNA fragment. This occurs during the PCR when the mixture is cooled to 55oC.

Answer 695

Non-cancerous cells. Benign cells can grow slowly to a large size; nuclei appear normal. Cells are often well differentiated; cells produce adhesion molecules that make them stick together so that they remain in the tissue. Tumours are surrounded by a capsule of dense tissue and so remain a compact structure.

Answer 696

The process by which a cell develops into a specialised cell with a specific function.

Answer 697

A strand of DNA formed from an RNA template, using the enzyme, reverse transcriptase. cDNA has no introns, only exons as it has the same base sequence as the coding strand of nuclear DNA .

Answer 698

The separation of negatively charged DNA fragments by differential movement towards the anode through an agarose gel in an electric field. The degree of movement is dependent on the mass of the DNA fragments and their net charge.

Answer 699

When separated DNA strands carrying the gene/nucleotide sequence to be identified, is mixed with a DNA probe, the probe binds to the complementary base sequence on one of the DNA strands. The site where the probe binds can be identified by the radioactivity or fluorescence emitted

Answer 700

An enzyme that can be used to catalyse the formation of phosphodiester bonds between the terminal nucleotides of DNA fragments

Answer 701

An enzyme which joins DNA nucleotides together during DNA replication and the polymerase chain reaction. Taq polymerase is an example of such an enzyme. This was originally obtained from bacteria in hot springs and is thermostable.

Answer 702

A short, single stranded length of DNA that either has nucleotides labelled with a radioactive isotope e.g. 32P or fluorescently labelled to emit light under certain conditions. DNA probes are used to locate a particular gene or DNA sequence.

Answer 703

The process of determining the order of nucleotide bases in samples of DNA. This is done by detecting the nucleotide bases A, T, C and G as they are added to a template strand by a polymerase enzyme.

Answer 704

A process where an electric shock is given to stimulate cells to take up pieces of DNA such as plasmids and bacterial artificial chromosomes

Answer 705

A relatively new scientific field which involves heritable changes in gene expression without changes in the base sequence of DNA. Epigenetics provides explanations as to how environmental influences such as stress, diet, toxins can alter the genetic inheritance of an organism's offspring.

Answer 706

The chemical tags which form a second layer around DNA and histones. The epigenome determines the shape of the DNA-histone complex. The epigenome keeps genes which are inactive in a tightly packed arrangement so that the nucleotide sequence cannot be read. [epigenetic silencing]. The epigenome unwraps active genes so that the DNA is exposed and can be easily transcribed.

Answer 707

The reading frame that contains each three letters of the genetic code for a polypeptide is shifted to the left or the right. A base deletion causes a frameshift to the left by one base. A base addition or a base duplication causes a frame shift to the right by one base.

Answer 708

Any change to one or more nucleotide bases or the rearrangement of bases in a section of DNA

Answer 709

The insertion of genes into cells to correct a genetic fault. This usually involves inserting a dominant gene into an individual who has two copies of a mutant recessive allele.

Answer 710

A diagnostic tool used in paternity cases, forensic science, plant and animal breeding and medical diagnosis e.g. Huntington's disease. The technique is based on the unique pattern of variable number tandem repeats. The number and length of VNTR's is different in all individuals except identical twins. The making of a genetic fingerprint consists of five stages: extraction of DNA and its quantity increased by PCR; digestion of DNA into fragments, separation of DNA fragments by gel electrophoresis; hybridisation where DNA probes bind to the VNTR's and then development to reveal the position of the DNA probes using southern blotting techniques.

Answer 711

The minimum quantity of genetic material that contains one set of all the individual genes ; in humans this is the DNA in 22 autosomes, the X chromosome and the Y chromosome plus mitochondrial DNA. Plant genomes include the DNA in chloroplasts

Answer 712

The application of the techniques of genetics and molecular biology to the mapping of genes on chromosomes and the sequencing of genes or complete genomes of organisms and viruses.

Answer 713

The insertion of genes into cells that differentiate into gametes so that the gene inserted is transmitted to future generations. Germ line cells are the zygote, early embryonic cells and all the cells that can develop into gametes in the ovaries and testes.

Answer 714

Any method in which the base sequence in samples of DNA, including whole genomes are determined in a short period of time.

Answer 715

A family of basic proteins which due to their overall positive charge bind to DNA in the nucleus and help condense it into chromatin. In eukaryotic cell nuclei, histones pack and order DNA into structural units called nucleosomes. When the DNA-histone complex is loosely packed/ less condensed, the DNA is accessible to transcription factors so that mRNA can form. Condensation of the DNA-histone complex inhibits transcription.

Answer 716

In glass'. The polymerase chain reaction.

Answer 717

The transfer of DNA fragments to a host cell using a vector.

Answer 718

A type of pluripotent stem cell that is produced from unipotent stem cells, which can be almost any adult body cell. The unipotent cells are genetically altered in the laboratory using protein transcription factors, to acquire the characteristics of embryonic stem cells. IPS cells are capable of self- renewal and could potential replace embryonic stem cells in medical research and treatment.

Answer 719

A group of bases become separated from the DNA sequence and re-join at the same position but in the inverse [back to front] order. The base sequence of this portion is reversed and affects the amino acid sequence that results.

Answer 720

Cancerous cells. Malignant cells can grow rapidly to a large size; nuclei appear larger and darker than normal. Cells become de- differentiated; cells do not produce adhesion molecules so that they break away/metastasise to other tissues to form secondary tumours. Tumours are not surrounded by a capsule of dense tissue, so can grow finger-like projections into the surrounding tissue

Answer 721

Used to identify whether a gene has been taken up by bacterial cells. They all involve a second separate gene on the plasmid such as resistance to an antibiotic; it may make a fluorescent protein which can be seen easily or it may produce an enzyme [e.g. lactase] whose action can be identified.

Answer 722

A process where methyl [CH3] groups are added to cytosine bases of DNA. Methylation usually inhibits transcription in two ways. It prevents the binding of transcription factors to DNA. It also attracts proteins that condense the DNA -histone complex so that the DNA is inaccessible to transcription factors.

Answer 723

These are found in mature mammals and can differentiate into a limited number of specialised cells of a particular type e.g. stem cells in the bone marrow can produce any type of blood cell. Examples of multipotent cells are adult stem cells and umbilical cord blood stem cells

Answer 724

Substances that increase the natural mutation rate in genes. Substances include high energy ionising radiation and short wavelength radiation such as X rays and UV light. Chemicals e.g. nitrogen dioxide; benzopyrene.

Answer 725

A mutation of a proto-oncogene, which then becomes permanently activated [switched on]. This occurs when a) the receptor protein on the cell surface membrane is permanently activated so that cell division is triggered in the absence of growth factors. b) the oncogene may code for a growth factor which is produced in excessive amounts, stimulating repeated cell division.

Answer 726

A sequence of nucleotides in double stranded DNA that is the same when read in one direction on one strand and read in the opposite direction on the complementary strand.

Answer 727

Circular lengths of DNA found in bacteria, which are separate from the main bacterial DNA. Many plasmids contain genes for antibiotic resistance. Plasmids can be used as vectors to transport DNA into host cells.

Answer 728

These are found in the embryos and can differentiate into almost any type of cell. Examples of pluripotent stem cells include embryonic and foetal stem cells. Pluripotent stem cells can divide in unlimited numbers and can be used to treat human disorders such as Parkinson's disease; macular degeneration; type 1 diabetes; skin grafts for burns and wounds.

Answer 729

An automated process that amplifies selected regions of DNA using alternate stages of polynucleotide separation [denaturation of DNA] and the replication of new DNA strands catalysed by DNA polymerase.

Answer 730

Short sequences of nucleotides used in the polymerase chain reaction. Primers have a set of bases complementary to those at one end of each of the two DNA fragments. Primers provide the starting sequences for DNA polymerase to begin DNA copying because DNA polymerase can only attach DNA nucleotides to the end of an existing chain.

Answer 731

The binding site for RNA polymerase to attach to a region of DNA, to enable the synthesis of mRNA during transcription.

Answer 732

All the proteins in a specific type of cell or organism at a given time, under specified conditions.

Answer 733

Proto-oncogenes stimulate a cell to divide when growth factors attach to a protein receptor on its cell surface membrane. This activates genes that cause the DNA to replicate and the cell to divide.

Answer 734

A type of DNA formed by combining DNA from two different sources such as human and plasmid

Answer 735

An enzyme which cuts across DNA molecules at specific sequences of bases, known as restriction sites, within the DNA molecule.

Answer 736

An enzyme that uses an RNA template to assemble a deoxynucleotide triphosphate molecules to form complementary DNA [cDNA].

Answer 737

Sometimes referred to as 'silencing RNA'. These are used in molecular biology to prevent translation after mRNA has formed. siRNAs are small sections of double stranded RNA. One of the two siRNA strands combine with an enzyme and the siRNA guides the enzyme to a mRNA molecule. When base pairing between the siRNA and mRNA occurs, the enzyme cuts the mRNA into smaller sections and can no longer be translated into a polypeptide.

Answer 738

The insertion of genes into body cells to correct a genetic fault in the individual concerned. The gene that has been inserted cannot be transmitted to the individual’s children as it is not in the cells that give rise to gametes/ sex cells

Answer 739

Occur when restriction endonuclease enzymes cut DNA in a staggered fashion. This leaves an uneven cut in which each DNA strand has exposed unpaired bases.

Answer 740

A region on a section of DNA which releases RNA polymerase and ends transcription.

Answer 741

A computer controlled machine used in the polymerase chain reaction that varies temperatures precisely over a period of time.

Answer 742

These can divide and produce any type of body cell e.g. zygote. Totipotent cells only occur for a limited time in early mammalian embryos.

Answer 743

A specific molecule e.g. oestrogen, which can move from the cytoplasm into the nucleus. Each transcription factor has a site which binds to a specific base sequence on DNA to trigger transcription of that base sequen

Answer 744

The process where 'naked DNA' [i.e. DNA fragments or plasmids] are taken up by a living recipient cell [i.e. bacterial cells] and recombined with the recipient cell's genome. Plasmids and bacterial cells are mixed together in a medium containing calcium ions. Calcium ions and changes in temperature make the bacterial membrane permeable, allowing plasmids to pass through the cell surface membrane into the cytoplasm.

Answer 745

The resulting organism which occurs when the DNA of two different organisms has been combined in a process called recombinant DNA technology. Sometimes referred to as a genetically modified organism.

Answer 746

A group of bases become separated from the DNA sequence on one chromosome and become inserted into the DNA sequence of a different chromosome. This affects the development of certain forms of cancer and also reduced fertility.

Answer 747

Slow down cell division, repair mistakes in DNA and trigger apoptosis [programmed cell death]. Tumour suppressor genes have the opposite role from proto-oncogenes.

Answer 748

These are found in mature mammals but they can only differentiate into a single type of cell. They are derived from multipotent stem cells and are made in adult tissue e.g. cardiomyocytes.

Answer 749

DNA bases which are non-coding. In every individual [except identical twins] the number and length of VNTR's is unique. The probability of two individuals having identical VNTR sequences is very small. However, the more closely related two individuals are, the more similar the VNTR sequences will be. This forms the basis of genetic fingerprinting , a diagnostic tool used in paternity cases, forensic science, plant and animal breeding and medical diagnosis e.g. Huntington's disease.

Answer 750

Any structure that is used to deliver a gene into a host organism in genetic engineering. Examples include viruses, plasmids and liposomes.