Module 2 Flashcards

Question

What are the 2 nucleic acids

Answer 1

deoxyribonucleic acid ribonucleic acid polynucleotides

Answer 2

1. phosphate group- PO4 2-, an inorganic negative acid. bonds to carbon 5 and 3 2. organic nitrogenous base containing 1 or 2 carbon rings and nitrogen 3. pentose sugar each component is joined by a strong covalent bond in 2 condensation reactions (image of phosphate, sugar and base joined)

Answer 3

Purine: Adenine and Guanine Pyrimadine: Cytosine, Uracil and Thymine (only one carbon ring- longer word but smaller molecule as its been CUT) (draw out images of the bases) purine bonds to pyrimidine so its symmetrical

Answer 4

-nucleotides are joined by phosphodiester bonds to form a sugar phosphate backbone chains of nucleotides join together to form nucleic acids only nucleotides of the same sugar can join -hydrogen bonds hold the double helix 3D structure between the bases. easily broken and reformed to allow DNA to replicate. complementary base pairing A-T 2 hydrogen bonds, C-G have 3.

Answer 5

anti-parallel strands

Answer 6

S-Pentose sugars D-deoxyribose sugar and ribose sugar on carbon 2 S-nitrogenous bases D-RNA has U instead of T S-sugar phosphate backbone D-Double/single strand S- Phosphodiester bonds/condensation reactions D-3 types of RNA-messenger, ribosomal and transfer S-nucleotides D-DNA/RNA nucleotides S-Order of nitrogenous bases forms a code on the nucleic acid (DNA+mRNA) D-DNA stores genetic information long term and bases code for aa which make proteins/RNA doesn't store code but copies it-protein synthesis D-DNA is big and stable RNA is small and unstable especially mRNA D-DNA in nucleus/ RNA in nucleolus and cytoplasm

Answer 7

- phosphorylated nucleotides that are made up of a ribose, adenine (nitrogenous base) and 3 inorganic phosphates energy storage molecules where energy can be released by breaking bonds between phosphates. -immediate store as used up as soon as made. instability of phosphate bonds in ATP means not good long term store. -A small amount of energy is needed to break (hydrolyse) the bond, but lots is released when the phosphate undergoes other reactions involving bond formation 30.6KJmol-1 - occurs simultaneously with energy requiring reactions -energy used in the breakdown of these molecules (respiration) is used to create ATP by attaching a phosphate to an ADP molecule-phosphorylation

Answer 8

* Small- moves easily in and out of cells * Water soluble- energy requiring processes occur in aqueous environments * Contains bonds between phosphates with intermediate energy- large enough for useful cellular reactions but not large enough that energy is wasted as heat * Releases energy in small quantities- for same reason as above * Easily regenerated- can be recharged with energy

Answer 9

1. The DNA helix unwinds 2. The 2 polynucleotide strands of DNA separate as the hydrogen bonds between the bases are broken by the enzyme helicase, which catalyses reactions to break them. 3. This unzips the DNA exposing the nitrogenous bases 4. Each new strand now acts as a template for the formation of a new molecule of DNA 5. Free DNA nucleotides base pair with the unpaired complementary bases. Complementary base pairing ensures exact copies are made 6. Then phosphodiester bonds form between the phosphate of one DNA nucleotide and the sugar of the next 7. The enzyme DNA polymerase catalyses the condensation reaction to covalently bond each nucleotide to the next. The sugar phosphate backbones of each new DNA strand are joined to form a DNA polymer 8. 2 genetically identical DNA molecules are formed, each containing one strand from the parent DNA and a new complementary strand- half parental DNA Is conserved. The strand that codes for a protein to be synthesised is a sense strand and rund from 5’ to 3’. The other strand is from 3’ to 5’ and is complementary to the sense strand and is also known as the antisense strand or the template strand. RNA is same bases as sense.

Answer 10

- The copying of DNA so that following cell division each new cell will have a full copy of all the original DNA. It is semi conservative replication, and produces geneticall identical sister chromatids - occurs during S phase - Must be copied accurately to conserve genetic information - Mutations are random an spontaneous changes in the sequence of bases in the DNA

Answer 11

Started growing bacteria in a medium containing heavy nitrogen isotope 15N, which the bacteria used to make nucleotides. The bacteria where then transferred to a normal 14N growth medium, and DNA samples were extracted over time and centrifuged. This separated the DNA according to density. The lowest strip contains purely 15N, the medium is hybrid DNA with 1 parental strand and 1 new DNA strand and the top is light DNA with just new strands. * Bacteria are used for this experiment as the replicate very fast so multiple generations and changes can be seen in a short period of time * Few ethical concerns * Reproduce asexually so less variation

Answer 12

A gene is a sequence of bases in DNA that codes for the codon which determine the sequence of aa in the primary structure of the polypeptide. this codes for enzymes which catalyse reactions to build a whole person. DNA contains the genetic code which codes for the synthesis of all polypeptides its contained in the nucleus to be conserved and protected Types of polypeptides are: - Structural proteins (keratin, collagen, actin, myosin) - Channel proteins - Enzymes - Cell surface receptors - Electron carriers - Haemoglobin - Antigens, immunoglobulins

Answer 13

A gene is a sequence of bases in DNA that codes for the codon which determine the sequence of aa in the primary structure of the polypeptide. this codes for enzymes which catalyse reactions to build a whole person. in-between genes is non coding DNA DNA contains the genetic code which codes for the synthesis of all polypeptides. genome is entire sequence of DNA with 25,000 genes its contained in the nucleus to be conserved and protected Types of polypeptides are: - Structural proteins (keratin, collagen, actin, myosin) - Channel proteins - Enzymes - Cell surface receptors - Electron carriers - Haemoglobin - Antigens, immunoglobulins

Answer 14

o A triplet code o Is degenerative (more than 1 codon codes for the same aa, which means mutations can be silent if the new triplet code codes for the same amino acid as the previous one) o It has punctuation o It is widespread but not universal ( most organisms have same code but different sequence of bases) o A non overlapping code (always in threes ensured by start codon) There are 4 bases arranged into triplets. 43 =64 options There are 20 amino acids 64-3 stop codons =61 61-1 met (start codon) = 60 options

Answer 15

1. The part of the DNA molecule to be transcribed unwinds and unzips as DNA helicase breaks the H bonds between bases, exposing unpaired nucleotides. Happens 3’ to 5’ of template strand. 1. Free RNA nucleotides form complementary base pairs with the unpaired bases on the template strand – hydrogen bonds. This starts at 5’ end of nucleotide and 3’ of mRNA 2. A binds with U and C binds with G, with 2 and 3 hydrogen bonds, purine to pyrimidine 3. Phosphodiester bonds (covalent) form between nucleotides to make the sugar phosphate backbone using the enzyme RNA polymerase. This occurs 5’ to 3’. 4. The template and coding strand reform hydrogen bonds, A-T ect. 5. The mRNA is complementary to the template strand and a copy of the coding strand 6. mRNA leaves to go to the ribosomes through the nuclear pore

Answer 16

- made in the nucleus and passes into the cytoplasm - it is a length of RNA that folds into hairpin shapes to form a clover leaf - it can bind to a specific amino acid in the cytoplasm where 3 exposed bases are - it can recognise the specific mRNA codon for the amino acid it carries by having 3 unpaired nucleotide bases at the other end which are anticodons for the amino acid - the other clover leaf recognises a specific activation enzyme - is the smallest RNA and there are over 20 After protein synthesis the RNA molecules are degraded in the cytoplasm- the phosphodiester bonds are hydrolysed an the RNA nucleotides are released and reused

Answer 17

1. mRNA attaches to the small subunit of a ribosome in the groove exposing 6 bases of the mRNA to the large subunit. Several ribosomes may attach to the mRNA at once forming a polysome. This means many identical polypeptides can be synthesised at once. and each makes a bit of the polypeptide all one polypeptide or several different 2. the first exposed mRNA codon is always AUG (start codon methionine) 3. the tRNA molecule with the amino acid metaphase has an anticodon complimentary to the 1st codon, and lines up in position P. 4. complimentary base pairs form H bonds between the codon and the anticodon (UAC with AUG) 5. another tRNA (pro) forms complimentary base pairs with the next codon in the ribosome at position A 6. the enzyme peptidyl transferase forms a peptide bond between the two amino acids (met and pro) 7. the first tRNA is released and leaves the ribosome without its amino acid 8. the next ribosome moves along the mRNA 3 bases exposing the next codon 9. the second tRNA molecule (pro) is now in position P 10. a new tRNA molecule pairs with the mRNA in position A bringing its amino acid (Tyr) 11. a growing polypeptide is formed in this way until a stop codon is reached 12. a stop codon (UAA, UAC or UAG) on the mRNA signals the ribosome to leave the mRNA. These work by having no tRNA with a complementary anticodon or the tRNA is codes for is not carrying an amino acid 13. a newly synthesised protein is now complete and can take up its tertiary structure ect. Needed for structure and fucntion 14. some proteins need to be activated by cAMP to take a 3D shape that is the best fit to their complementary molecule eg. By binding to an allosteric site on an enzyme

Answer 18

R-Both processes have DNA as template but both strands are used as template strands T-Has a template strand and a coding strand R-Whole molecule is unzips and unwinds and is replicated T-Only part of a DNA molecule (gene) unzips and unwinds at a time R-Activated free nucleotides to bond to, but DNA nucleotides T-Activated free nucleotides to bond to but RNA nucleotides R-Both use polymerase to form phosphodiester bonds to produce a backbone but DNA polymerase T-Both use polymerase but RNA polymerase R-Both use complimentary bases with hydrogen bonds but AT GC T- AU GC R-Product is 2 daughter strands identical to templates T-Product is 1 mRNA strand R-DNA stays in nucleus T-mRNA leaves through nuclear pore to go to cytoplasm R- both unwinds and unzips T- unwind and unzip

Answer 19

o DNA stays in nucleus o Proteins are made on ribosomes in the cytoplasm (ribosomes made in nucleolus from rRNA and protein) o Genetic code is copied to messenger RNA which can leave the nucleus by nuclear pores as its smaller taking the code to the ribosomes transported by the cytoskeleton

Answer 20

INTERPHASE Growth 1: normal cell growth and specialisation. proteins from which organelles are synthesised are produced Synthesis: DNA replication Growth 2: synthesis of organelles so there's enough in new cells. DNA starts to coil into visible chromosomes at end. MITOSIS (cytokinesis)

Answer 21

mitosis is when the nucleus splits (growth, repair and asexual reproduction) cytokinesis is when rest of cell splits and is the end of mitosis

Answer 22

by asexual reproduction or form a zygote from a female and male gamete

Answer 23

the process by which a cell develops to become more distinct in form and function

Answer 24

enzymes check replicated DNA for errors if errors are detected they are repaired or the cell destroys itself to stop mutations being passed on G1:chromosomes checked for damage and DNA repaired before S phase. If the cell doesn’t satisfy the requirements of the checkpoint, then it enters the resting state G0. s: check that all chromosomes have been replicated- the cycle will stop if not G2:another check for DNA damage that may have occurred during replication, and cycle may be delayed to repair Metaphase:check whether chromosomes have attached correctly to spindle fibres before anaphase

Answer 25

the part of the cell cycle where the cell is not undergoing cell division

Answer 26

The phase when the cell leaves the cycle either temporarily or permanently. It does this because: • Differentiation: a cell that becomes specialised to carry out a particular function is no longer able to divide so will not renter the cycle. red blood cells can't divide as they loose their nucleus in development • The DNA may become damaged so is no longer viable and cant divide so enters permanent cell arrest • The majority of normal cells only divide a limited number of times and eventually become senescent. As you age, the number of these cell in your body increases leading to age related diseases like cancer and arthritis • Lymphocytes can be stimulated to go back into the cell cycle and start dividing again in an immune response

Answer 27

homologous chromosomes are 2 chromosomes with the same sequence of genes on them- one from father and one from mother. they may have different alleles

Answer 28

DNA wrapped around histone proteins | when it becomes supercoiled it forms visible chromosomes. after G2 as they can't function when coiled

Answer 29

before cell divides the DNA replicates (synthesis) producing a chromosome made of a pair of sister chromatids held together by a centromere. they need to be kept together during mitosis so they can be segregated equally, one to each daughter cell

Answer 30

- Replacement of cells EG. outer layer of skin replacement of epidermal cells, red blood cells, intestinal lining cells - Growth of tissues by producing new extra cells – EG. epithelial tissue, plant meristem cells (stem and root growth). - Division of zygote into a multicellular organism where, all cells are genetically identical. - Formation of clones of T and B lymphocytes and plasma cells in the immune response - Asexual reproduction where mitosis produces individual organisms which are genetically identical to each other (clones) and the parent cell – EG. binary fission in bacteria(not asexual as no nucleus), budding in yeast. - The production of genetically identical cells in multicellular organisms allows certain cells to retain the ability to develop into any other type if needed as a result of damage. - Sometimes, abnormal cells divide by mitosis in an uncontrolled way giving rise to tumours, and if the cells are malignant, cancers.

Answer 31

the equator of the cell is constricted by a ring of contractile proteins (actin) in the process of cleavage to create 2 cells in plant cells, cleavage can't form as there is a cell wall and no centrioles. so vesicles from the Golgi assemble at the equator and fuse with each other and the cell surface membrane to divide the cell new sections of wall form along the new sections of membrane. if they were formed before daughter cells separated lysis would occur some vesicles remain intact to make connecting channels- plasmodesmata, through the new cell wall

Answer 32

INTERPHASE: chromosomes replicated and its checked for errors PROPHASE (plump): start- chromosomes supercoil, nucleolus starts to disappear, centrioles move to opposite poles and organise formation of microtubules that will form the spindle- spindle starts to form end- chromosomes consist of a pair of chromatids joined by a centromere, nucleolus disappears and nuclear envelope breaks down METAPHASE: (middle) start-Microtubules of the spindle attach to the centromeres from either side which are aligned in the middle. The attachment involves a protein structure on each chromatid called a kinetochore. end-The microtubules pull in opposite directions on the centromere so that they pull apart Homologous chromosomes don’t associate. ANAPHASE: (apart) start- The chromatids are pulled to opposite poles of the cell by spindle fibres which shorten, centromeres leading (V-shape). end-chromosomes reach their destination TELOPHASE: (two) start-Chromatids now called chromosomes. The spindle fibres break down. The cells start to constrict around the middle end-New nuclear envelopes and nucleolus’ form around each group of chromosomes. The chromosomes slowly uncoil I Peed on a MAT, C?

Answer 33

• The first stage is when homologous chromosomes are separated into two cells, each containing 1 full set of genes so are haploid due to reduction division • The second stage is where pairs of chromatids are separated forming 4 haploid daughter cells that are unidentical providing genetic variation PROPHASE 1: centrioles replicate and move to poles to form spindle, chromosomes condense as sister chromatids after replicating in interphase, nucleolus disappears, and nuclear envelope disintegrates. Crossing over as chiasmata form between homologous pairs of chromosomes (X X) (bivalents when they are close together, 4 chromatids- tetrad). When exchange occurs it forms recombinant chromatids. They may be different alleles of the same gene so sister chromatids are no longer identical. METAPHASE 1: bivalents line up randomly along the metaphase plate and independent assortment occurs. Microtubules attach to centromeres. ANAPHASE 1: Separation of homologous chromosomes in each bivalent by contracting microtubules. Each chromosome still has 2 sister chromatids joined together. TELOPHASE 1: usually telophase 1 and interphase 2 doesn’t occur in plants but in animals chromosomes assemble at each pole, cytokinesis occurs (leaves small cytoplasmic bridges between cells) and new nuclear membranes forms during telophase, chromosomes uncoil and a very rapid interphase may occur. PROPHASE 2: centrioles replicate and move to poles whilst new spindle fibres form at right angles to previous spindle axis. The chromosomes condense and become visible again and nuclear envelope breaks down if it reformed. No chiasmata METAPHASE 2: individual chromosomes consisting of 2 sister chromatids line up alone on the metaphase plate. Microtubules attach to centromeres. Independent assortment occurs. ANAPHASE 2: individual chromosomes are now separated into chromatids by being pulled to opposite poles after division of centromeres TELOPHASE 2: 4 haploid genetically different cells are produced as chromatids assemble at poles. Chromosomes uncoil and form chromatin again. Nuclear envelope reforms and nucleolus becomes visible. diagram

Answer 34

asexual: environmental influences Sexual: CROSSING OVER A pair of joined homologous chromosomes – a bivalent with a chiasmata may exchange DNA between non sister chromatids of homologous chromosomes during prophase 1. This creates a new combination of alleles in chromatids, but doesn’t change genetic information as chromosomes have identical sequences. They come together in a process called synapsis INDEPENDENT ASSORTMENT The random orientation of homologous chromosomes on the equator in metaphase 1 determines the direction in which the pairs of chromatids move in anaphase 1. different combo of alleles. 2n genetically different gametes could be made where n is the haploid number of chromosomes In metaphase 2 the random orientation of pairs of chromatids determines which chromosomes migrate to opposite poles of the cell. FUSION of male (spermatozoa)and female gametes(secondary oocyte) which are genetically different to produce a zygote is completely random creates a large number of allele combinations RANDOM MUTATIONS cause different bases so different polypeptides as DNA checks don't recognise damage

Answer 35

mitosis: no chiasmata form Meiosis: bivalents are formed when homologous chromosomes are paired up in prophase 1 and chiasmata may form Mitosis:Individual chromosomes line up along equator in metaphase Meiosis: Homologous pairs of chromosomes assemble along the equator in metaphase 1 Mitosis:Chromatids are pulled to opposite ends of cell Meiosis: Homologous chromosomes are pulled to the opposite poles and chromatids stay joined together in anaphase 1 first division ends up with haploid

Answer 36

measures ratio of cells in mitosis to the number of cells counted used to diagnose cancer as a measure of cell proliferation high in growing areas like tips and roots number of cells in mitosis/ total number of cells

Answer 37

a structure formed in the early development of mammals containing embryonic stem cells that will create body cells as well as placenta and umbilical cord. (totipotent) It is not yet implanted in the womb. It is made of an outer layer of cells, a fluid filled space and a group of cells called the inner cell mass, which is where the embryo cells are found

Answer 38

starts with the fertilised egg- 1 cell divides in 2 to produce 2 daughter cells then divides again and so on they can self renew by making copies of themselves and also differentiate to make specialised cells. when they divide they produce 2 stem or 2 specialised, not one of each the DNA in stem cells and the daughter specialised cell is the same, as there are lots of other molecules inside and around cells that can change the way cells behave in the case of differentiated cells specialised cells can't divide and make copies of themselves, so stem cells are needed to replace specialised cells that die, get damaged or used up(liver and T cells can)

Answer 39

embryonic found in the blastocyst | tissue/adult found in tissues of the body(foetus, baby child or adult)

Answer 40

pluripotent: Can make all types of specialized cells in the body. Embryonic stem cells are pluripotent Multipotent: Can make multiple types of specialized cells, but not all types. Tissue stem cells are multipotent as they can only make the kind of cells found in the tissue they belong to- blood cells can make cells found in blood Totopotent: can differentiate into all types of specialized cells in the body PLUS cells that are needed during development of the embryo only: placenta, yolk sac, umbilical cord. Eg. Zygote Unipotent: can only differentiate into one type of specialized cell. For example, spermatogonial stem cells (found in the testicles) are unipotent because they can only form sperm cells.

Answer 41

* To treat diseases * Understand how diseases develop * Test drugs in lab * Umbilical cord stem cells are very good because they are plentiful supply and non-invasive surgery, and can be stored in case the individual ever needs them without rejection gender, age

Answer 42

• HEART DISEASE- muscle tissue in the heart damaged from heart attack • TYPE 1 DIABETES- grow insulin producing cells to transplant into a patient with diabetes • PARKINSON'S DISEASE- Replacing dopamine producing brain cells that die causing shaking and rigidity. • ALZHEIMER'S DISEASE- brain cells destroyed from build up of abnormal proteins. Stem cells are beig grown into nerve cells. Hard because damage to brain is widespread. • MACULAR DEGENERATION- condition responsible for causing blindness in elderly and diabetics. Can grow retinal cells. • BIRTH DEFECTS- have successfully reversed birth defects in mice • SPINAL INJURIES- some movement has been restored in rats by introducing stem cells into site of spinal injuries to repair damage • BLOOD DISEASES- eg. Sickle cell disease using bone marrow and stem cells CURRENT: • BURNS- stem cells grow on biodegradable meshes to produce new skin quicker than normal graft process • DRUG TRIALS- potential new drugs can be tested on cultures of stem cells before being tested on animals and humans • DEVELOPMENTAL BIOLOGY- the study of the changes that occur as multicellular organisms grow and develop from a single cell like a fertilised egg and why things sometimes go wrong

Answer 43

• Cells from the body go through genetic reprogramming- certain genes are added to their cell so that the iPS behaves like an embryonic stem cell. These are then cultured in a lab so that they differentiate into specialised cells. From multipotent to pluripotent. Parkinson’s or Alzheimer: • Take cells like skin cells from body • Make iPS cells • Use those iPS cells to grow specialised cells needed eg. Brain cells. They wouldn’t be rejected as they would be from their own body

Answer 44

won Nobel prize for adding 4 genes and in a few weeks the cells behaved like stem cells

Answer 45

* Embryos used to be donated from left over fertility clinics, but the law has changed recently so that embryos can be specifically created in the laboratory as a source of stem cells * Usually the removal of stem cells from embryos destroys the embryos but techniques are being introduced to prevent damage- moral and religious objections as murder. There are debates over weather the embryo has rights and who owns the genetic material being used for research * The use of umbilical cord stem cells overcomes the ethical debate, but these cells are only multipotent, not pluripotent like embryonic * Adult stem cells could also be used but don’t divide as well as umbilical and are more likely to have mutations, therefore iPS is occurring * Plant stem cells don’t have the same ethical issues and are used to create drugs cheaply and unlimited supply

Answer 46

The process of physical changes by which a cell develops to become more distinct in form to carry out a particular function how the physical changes of differentiation allow an organism to perform its function

Answer 47

o Flattened biconcave shape to increase SA to vol ratio for transport of oxygen o No nuclei or many other organelles increasing space for haemoglobin o Flexible, elastic membrane to change shape to squeeze through narrow capillaries o Cytoplsam contains lots of haemoglobin (280mill molecules) pigment binds with oxygen and relases it when concentrations are low develop large numbers of ribosomes early in differentiation to make haemoglobin

Answer 48

o indentation of nucleus to make it multi-lobed so it's easier to squeeze through small gaps to get to sight of infection. May be due to flexible membrane. o development of granular cytoplasm contains many lysosomes containing hydrolytic enzymes used to attack pathogens o Flexible nuclear membrane shape allowing them to penetrate between junctions of the cells of the capillary wall and to form pseudopodia to engulf microorganisms o Called neutrophils as granules don’t stain darkly with acidic or basic dyes o Destroy foreign bodies by engulfing them by phagocytosis and secreting enzymes

Answer 49

o Responsible for transport of water and minerals throughout plants o Tissue is composed of vessel elements which are elongated dead cells o Walls strengthened with lignin providing structural support and waterproof o Wide lumen and absent end walls allows water flow without blockages o No cytoplasm as its unnecessary for strengthening and would obstruct water transport

Answer 50

o Parenchyma cells are not specialised and form a packaging tissue between other cells o Vessel elements are the main water transporting cells and have a wide lumen and end walls are perforated or completely absent. Pits allow water to move laterally, which can be helpful for avoiding blockages. Vessels are aligned so are continuous and stretch the length of the plant. o Tracheid’s transport water in angiosperms they also help strengthen tissue. Don’t have a wide lumen but have perforated end walls and pits where cell wall is very thin, and water can move easily between cells. o Fibres don’t transport water they just provide support. They have hardly any lumen and are just strips of lignin.

Answer 51

o Responsible for transport and of organic nutrients, particularly sucrose, from leaves and stems where it is made by photosynthesis to all parts of plants where it is needed o Composed of columns of sieve tube cells separated by perforated walls called sieve plates connecting cytoplasm of cells o Few organelles o Reduction of cytoplasm means they cannot support themselves so have companion cells o Plasmodesmata allows molecules to pass between plant cells through cytoplasm

Answer 52

o Sieve tube elements are the cells that transport nutrients o Companion cells help support the sieve tube elements, and have a large number of mitochondria and ribosomes so we think they play a role in transport o Phloem parenchyma also are packed between cells fibres and sclereids with thick. cell walls for support

Answer 53

o Cambium tissue in stems and roots divides to form phloem cells on the outside and xylem on the inside o Cambium is an example of meristem- undifferentiated plant tissue and is pluripotent o The production of xylem and phloem is stimulated by hormones. o The balance of different hormones can shift production between xylem and phloem o The outer cambium cells produce phloem and the inner produce xylem o The cells that become xylem lose their cytoplasm and deposit lignin in their cell walls. The end cell walls may be lost. o The cells that become phloem loos some cytoplasm and organelles and develop sieve plates at the end of cells.

Answer 54

o Made of specialised squamous epithelial cells o Very thin due to flat/squat cells and is only 1 cell thick, helping rapid diffusion across a surface o Forms lining of lungs and allows rapid diffusion of oxygen into blood

Answer 55

o Made of ciliated epithelial cells o Cells have hair like structures called cilia on one surface that move in a rhythmic manner to move substances o Lines trachea to sweep mucus away from lungs o Goblet cells are also present releasing mucus to trap any unwanted particles in air like bacteria, so they don’t reach the alveoli

Answer 56

o Male gametes that deliver genetic information to female gamete (ovum) o Have a flagellum to help with movement o Contain many mitochondria to supply the energy needed to swim o Acrosome head contains digestive enzymes released to digest the protective layers around the ovum allowing the sperm to penetrate

Answer 57

o Many chloroplasts to absorb as much light as possible for photosynthesis. They can also move within the cytoplasm in order to absorb more light o Cell is tall and thin to allow light to penetrate further before having to go through a second cell wall, as cell walls absorb or reflect some light o Rectangular box shapes can be closely packed to form a continuous layer o Thin cell wall, increasing rate of diffusion of carbon dioxide o Large vacuole to maintain turgor pressure

Answer 58

o Form small openings called stomata o Close when loose water by osmosis o Cell wall is thicker on one side so doesn’t change shape symmetrically as its volume changes

Answer 59

o Root hairs are long projections from cell penetrating between soil particles to reach more water and increases surface area for absorption of minerals and water vacuole contains cell sap with ions and sugars to lower water pot. o Present at the surfaces of roots near the growing tips

Answer 60

o Made of muscle and nerve tissue blood and connective tissue. o Have skeletal (voluntary), smooth (involuntary), cardiac (in heart). o Skeletal muscle cells are highly specialised and are multinucleate, and often referred to as muscle fibres, which group together to form a fascicle, and groups of these form muscle. o The muscle fibres contain the contractile protein myofilaments called actin and myosin which are formed into structures called myofibrils.

Answer 61

o A connective tissue composed of specialised cells called chondrocytes that produce extracellular matrix consisting of collagen fibres stiffening and strengthening the tissue, and elastin fibres giving it flexibility. o Function is to protect and strengthen, found in joints, nose, ear, rib cage, trachea. Many fish have no bone, only cartilage

Answer 62

a group of differentiated cells that work together to perform a specialised function o Plant: - Epidermis- adapted to cover plant surfaces (single layer of closely packed cells covered by waterproof waxy cuticle. Contains stomata) - Vascular- adapted for transport of water and nutrients eg. Xylem and phloem o Animal: - epithelial- adapted to cover body surfaces, internal and external - nervous- transmission of electrical impulses - muscle-adapted to contract - connective- adapted to hold other issues or as a transport medium

Answer 63

Organ: a group of different tissues that work together o Plant: the leaf carry’s out photosynthesis and gas exchange. It has xylem to bring water, phloem to take organic nutrients away, palisade and spongy parenchyma carrying out photosynthesis, epidermis waterproofing leaf and has stomata. o Animal: the heart pumps blood around the body. Cardiac muscle requires nutrients and oxygen for respiration, supplied throughout the blood. Coordination is provided by nervous tissue.

Answer 64

a number of different organs working together to carry out a major function in the body o Plant: gaseous exchange system o Animal: - Digestive system takes in food, breaks down large insoluble molecules into small soluble ones, absorbs nutrients into blood, retains water and removes undigested material. Involves oesophagus, stomach, small and large intestine, liver, pancreas, and gall bladder. - Cardiovascular system moves blood around body to provide an effective transport system for the substances it carries

Answer 65

Erythropoiesis- the process by which an erythrocyte is formed always formed from stem cells as have no nucleus so can't divide themselves Multipotent bone marrow stem cells differentiate Proerythroblast- changes to have a large nucleus containing several nucleoli surrounded but a small amount of cytoplasm so now only able to become an erythrocyte Haemoglobin then accumulates in the cytoplasm Nucleus is ejected from the cell Undergoes further changes like changing shape to biconcave disk to become a mature erythrocyte

Answer 66

1. only 1 parent required so saves time and energy finding a mate or waste of gametes- pollen that doesn't result in fertilisation 2. genetically identical offspring if an organism is well adapted its passed on 3. dispersal and spread is quick 4. rapid multiplication so large numbers of individuals can be produces very quickly to help survival

Answer 67

1. no genetic variation unless mutation so evolution my natural selection doesn't occur so unlikely to survive changes in environment 2. rapid colonisation may lead to overcrowding and exhaustion of resources

Answer 68

genetic variation through natural selection

Answer 69

requires a lot of time and energy in comparison to asexual reproduction

Answer 70

carbon, hydrogen, oxygen carbon, hydrogen, oxygen carbon, hydrogen, oxygen, nitrogen, sulfur carbon, hydrogen, oxygen, nitrogen, phosphorus

Answer 71

o Monomers are joined together to form a polymer o Anabolic o Water molecule is released o Covalent bond formed- oxygen bridge

Answer 72

o A chemical reaction that splits polymers into monomers o Catabolic o Water molecule is used o Covalent bond is broken- enzyme needed

Answer 73

monosaccharide and polysaccharide amino acid and polypeptide nucleotides and DNA+RNA

Answer 74

o Hydrogen bonds form between polar molecules o They break and reform constantly between the moving water molecules o Polar molecule occur when in a covalent bond, the electrons are not shared equally amongst atoms of different elements. When atoms spend more time closer to one atom than other, you get polar molecules, with slightly negative and slightly positive ends. o Weak individually but strong in large numbers o Shown by a dotted/dashed line o Liquid at room temp, but densest at 4 degrees Celsius

Answer 75

``` habitat solvent transport temperature regulation reactant ```

Answer 76

o High specific heat capacity due to hydrogen bonds restricting the movement of water molecules so aquatic habitats are stable. Mammals don’t have to endure rapid and extreme temperature changes, and can keep internal body temperature constant- enzymes and metabolic rate o Ice has lower density than water because of its lattice arrangement-4 hydrogen bonds to other water molecules, which provides a habitat (swim and move) and an insulating layer so organisms in water can survive. Prevents bottom of water freezing too which would kill organisms and allows currents/nutrients to circulate. o Surface tension due to cohesion between water molecules below rather than air creates a skin which insects such as pond skater can be supported on o Colourless nature means photosynthesis can occur at depth

Answer 77

o When chemical dissolves in water its free to move and react with other chemicals- cytoplasm o Water is polar so can attract other charged or polar covalent molecules EG. In blood and sap used for transport, glucose and sucrose are polar molecules o Stability to cell membrane is obtained as its hydrophobic

Answer 78

o Blood and tissue fluid transport many substances in and out of cells as is a solvent o Water helps xylem and phloem function as the hydrogen bonds that hold water molecules together give it cohesive properties, making long columns of water molecules that don’t break. Adhesion occurs between walls of xylem and water helping water get drawn up vessels- capillary action. o viscosity allows water to flow byt slows doewn water loss from pores in plants

Answer 79

o High latent heat of vaporisation so when you sweat it transfers a lot of energy when it evaporates due to hydrogen bonds being broken o Transpiration stream in plants is similar

Answer 80

number carbons | C must bond to O but H can be either side

Answer 81

Pentose sugars have 5 carbons o RNA- 5 membered ring with 4 carbons On carbon 2 there is a hydroxyl group o DNA- 5 membered ring with 4 carbons On carbon 2 there is just hydrogen

Answer 82

Hexose sugars have 6 carbons o Glucose- 6 membered ring with 5 carbons Soluble as OH group is free to interact with water o Fructose- 5 membered ring with 4 carbons- naturally found in fruit o galactose

Answer 83

water soluble | reducing sugars

Answer 84

Alpha glucose: o Down, down, up, down-OH o Hydroxyl group is below carbon 1 in alpha Beta glucose: o Up, down, up, down o Hydroxyl group is above carbon 1 in beta Animals and plants have enzymes that can only break down a glucose to release energy needed to make ATP in respiration B glucose cannot be used for energy but is used for structure and cellulose

Answer 85

o Place the sample in a boiling tube with an equal amount of benedict’s reagent. Either dissolve or grind it if not liquid. o Must heat at 80 degrees for reaction to occur for about 5 minutes o The reducing sugars will react with the blue copper sulphate solution in the benedict’s reagent reducing cu2+ ions to brick red cu+ ions. o Green- yellow-orange-brick red precipitate shows increasing quantities o For non-reducing sugars, you need to boil them with HCL it will then test positive as it is hydrolysed by the acid to form reducing sugars. You must neutralise the acid first. o Can be made quantitative by using a colorimeter- a piece of equipment used to quantitatively measure the absorbance or transmission of red light- more concentrated will be less blue as the blue benedict’s solution is used up in the reaction with the sugar. Therefore more red light is transmitted. o You put a filter in the colorimeter then calibrate it using distilled water. The solutions being tested must be filtered first to remove precipitate. o Reagent strips can be used to test the presence of reducing sugars. With the use of a colour coded chart, the concentration of the sugar can be determined. An alternative to this is to filter the precipitate, dry it and weight it, where more precipitate means more concentrated

Answer 86

form disaccharides then polysaccharides | 1-4 glycosidic bond is formed

Answer 87

maltose- 2 alpha glucose sucrose- alpha and fructose lactose- alpha/beta glucose and beta galactose reducing sugars like maltose and lactose as can donate electrons to another molecule sucrose is non reducing sugar as the glycosidic bond formation is different so must first be hydrolysed by acid in hot water bath/enzyme into its constituent where once neutralised will test positive for Benedict's

Answer 88

* Maltose and lactose both contain the same number of each element * Both bonded by 1-4 glycosidic bonds * Have 2 6 membered rings each * Have 2 CH2OH groups * Rings contain 1 oxygen atom * Lactose has 1 glucose monomer and one galactose monomer whearas maltose has 2 glucose monomers * Lactose has beta glucose maltose has alpha glucose * Beta glycosidic bonds alpha glycosidic bonds * Monomers flipped in lactose and same direction in maltose

Answer 89

cobalt chloride paper goes from blue to pink

Answer 90

iodine dissolved in potassium iodide solution o The long chains of amylose coil into a spring shape making the amylose molecule quite compact o Iodine molecules can become trapped in the coils of the spring to form an amylose-iodine complex o The formation of this complex changes the colour of iodine from brown to blue/black

Answer 91

Structure: Chain of alpha glucose monomers. Compact and stable because of coils so good storage molecule Function: Energy store in plant. Glucose made by photosynthesis is stored as starch. bond: 1-4 glycosidic bond with hydrogen bonds holding the OH groups inside coil together making it more compact shape: Linear molecule that coils due to angle of bond. properties: Slightly soluble as OH group sticks out so can make hydrogen bonds with water, but some are bonded. Less soluble than amylopectin or glycogen.

Answer 92

structure: Chains of alpha glucose monomers with other chains branched off. Compact. function: Energy store in plants eg. In potato tuber its stored in amyloplasts within cells and in chloroplasts Bond: 1-4 glycosidic bond between alpha glucose and 1-6 gylcosidic bonds to add a new strand (to join the 2 chains of amylose) shape: Branched molecule every 25 glucose subunits Properties: Slightly Soluble as OH group sticks out so can make hydrogen bonds with water

Answer 93

Structure: Similar to amylopectin but has many more branches (1-6 bonds) which make the ends more accessible to enzymes giving a quicker release of energy and makes it more compact. Function: Energy storage in animals- stored as granules in animal cells like liver and muscle cells. Large molecule so doesn’t leave liver cell where made but bonds are hydrolysed to release alpha glucose into blood Bond: 1-4 glycosidic bond between alpha glucose. These chains tend to be shorter so less likely to coil, and more compact. 1-6 gylcosidic bonds to add a new strand Shape: Branched molecule Properties: Doesn’t change osmotic potential of cell when stored as glycogen as it is insoluble. Most soluble as has the most branches so can make the most OH bonds

Answer 94

Structure: Alternating molecules of beta glucose rotate 180 degrees, preventing spiral. Bundles of microfibrils (40-70 cellulose chains) are also crosslinked by hydrogen bonds to form macrofibrils then fibres. This is a very stable and strong structure. Function: Structural support and rigidity in plants eg. Cell walls Bond: Beta glucose held together by gylcosidic bonds and chains held together by hydrogen bonds forming microfibrils. Shape: Straight chains to form microfibrils Properties: Insoluble as the OH groups are involved in hydrogen bonds so can’t make hydrogen bonds with water High tensile strength

Answer 95

o There are 20 amino acids, 8 essentials and 12 non essentials. 20x20x20 for all combo’s o Amino acids are basic monomer units of proteins made of an amino and carboxyl/organic group by condensation reactions which create dipeptides then polypeptides main peptide bonds and releasing water

Answer 96

plants can manufacture their own amino acids using nitrates from the soil and organic molecules made by photosynthesis Animals can only make non-essential amino acids from essential amino acids obtained from the diet. Can’t store excess amino acids because the amino group makes them toxic- in solution is ammonia They are transported to the liver where the amino group is removed (deamination) and then converted into urea and excreted in urine via the kidney. keto acid is respired if the R group contains C, O or H it can also be respired if if was amine it would be converted into urea

Answer 97

DO NOT HEAT o Detects presence of peptide bonds o Contains copper sulphate and alkaline potassium hydroxide o A blue ring first appears and when shaken will turn the solution purple o Relies on reduction of cu(II) ions to cu(I), which forms a violet complex with the nitrogen component of the peptide bond in an alkaline solution

Answer 98

o Protease enzymes control formation and breakage of peptide bonds in organisms o Pepsin is a type of protease and digests protein in the stomach o Protease regulates the breakdown of protein hormones, so their affects are not permanent o Older skin is less able to build the protein collagen as it lacks enough of the correct enzyme resulting in aging.

Answer 99

the sequence of aa in a polypeptide o It determines the structure and function of the protein o The sequence is coded for in the DNA in the nucleus o Held together by peptide bonds- this reaction is catalysed by the enzyme peptidyl transferase present in ribosomes, the sites of protein synthesis

Answer 100

the chain of amino acids takes one of these 2 shapes: o An alpha helix or a beta pleated sheet (chains lie parallel an appear pleated due to pattern formed by individual amino acids) o This is determined by the R groups and the order of amino acids determines where the bonds form so what shape occurs o There are hydrogen bonds between chains in both structures creating these shapes

Answer 101

the secondary structure then further coils into its final 3D shape o Determines the 3D shape of the and therefore its function- give active site This causes the following interactions between R groups: o Disulphide bonds- the amino acid cysteine contains sulfur (R group) where 2 cysteines are found close together and a covalent bond forms o Ionic bonds- R groups sometimes carry a charge and where opposite charged amino acids are close together, they form an ionic bond (affected by pH as affects charge ratio) (strongest) o Hydrogen bonds- where slightly positive groups are found near slightly negative groups (weakest). O- H+ o Hydrophobic and hydrophilic reactions- proteins are assembled in a water-based cytoplasm, so the way in which the protein folds depends on whether the R groups are hydrophilic or phobic. Hydrophilic amino acids tend to be found on the outside in globular proteins and hydrophobic in the centre o Van der waals forces- several aa have large hydrocarbon groups in their side chains which can attract or repulse each other creating weak bonds

Answer 102

o Quaternary structure: When a protein is made from more than 1 polypeptide chain or subunit- they can be the same or different. Enzymes have identical subunits whereas insulin has 2 different. o A sub unit is a single polypeptide o The polypeptides are bonded together by ionic, hydrogen and hydrophilic/phobic bonds like tertiary, but these interactions occur between different protein molecules rather than within 1 molecule

Answer 103

is formed from long parallel insoluble molecules, due to presence of a high proportion of amino acids with hydrophobic R groups in their primary structures. Linked by disulphide bonds. They contain a limited range of amino acids with small r groups and is very repetitive leading to organised structures. They make strong long molecules not folded into complex 3D shapes. EG keratin Elastin Collagen

Answer 104

is a polypeptide chain coiled and folded into a spherical shape are compact, water soluble. Form when proteins fold into their tertiary structures so that hydrophobic R groups are on the inside away from aqueous environment. Used for metabolic reactions, immunity, muscle contractions EG. Haemoglobin has 4 subunits, with 2 sets of identical subunits. Insulin Catalyse/ enzymes Similarities: a number of different types of bond stabilise the molecules and hold it in place and are both polypeptides made from combinations of 20 amino acids

Answer 105

o An analytical device for the quantitative measurement of a biological response. o Molecular recognition- It usually uses an immobilised antibody which can specifically interact with an analyte and produce physical, chemical or electrical signals that cause a change in a transducer, causing it to release an immobilised dye on a test strip or an electric current in a glucose testing machine (transduction) signal is amplified. o An analyte is a compound (e.g. glucose, urea, drug, pesticide) whose concentration is being measured. o Display- this then produces a visible qualitative or quantitative signal such as a particular colour on a test strip or reading on a machine. o A blood glucose biosensor uses FAD combined with the enzyme glucose oxidase which oxidises the glucose and the released electrons reduce the FAD (enzyme) and leads to an electrical current being generated as the transducer takes the electrons by oxidising the FAD. The current is a measure of glucose concentration. Blood is put on a test strip which is inserted into the biosensor meter which displays it as a digital figure.

Answer 106

``` Ca2+: Bone structure, Muscle contraction Synaptic transmission Amylase cofactor Na+: Nerve transmission Counter current multiplier in LOH/CD Kidney function K+: Nerve transmission Guard cell opening H+: H bonds Blood pH ETC in resp and phs Catalysis NH+ 4: Formed from deamination of amino acids Needed for production of nitrate ions by bacteria ```

Answer 107

``` NO-3:N source for plants to build AA HCO-3:CO2 transport Plasma buffer Blood pH Cl-: Cl- shift in CO2 transport Amylase cofactor Balances positive charge of K and Na ions in cells PO-3 4: In phospholipids, cell membrane ATP and nucleic acids formation Bone formation OH-:Involved in bonds pH determination catalysis of reactions ```

Answer 108

Dilution factor: volume added/total volume | serial dilution: volume added/total volume x previous answer for concentration

Answer 109

distance moved by solute/distance moved by solvent

Answer 110

o They are partially permeable barriers, controlling what passes through them. o They are involved in cell signalling (communication between cells)-target cells o Site of chemical reactions o They provide attachment sites for enzymes and other molecules involved in metabolism. E.g. Cristae in mitochondria o They can allow electrical signals to pass along them. o They produce different compartments inside cells. (compartmentalisation) e.g. In lysosomes it can provide right conditions like PH of 4.8

Answer 111

gorter and grendel in 1925 a the phospholipid bilayer 1935 Davson-danielli proposed model with proteins 1970s singer and Nicholson showed fluid mosaic model

Answer 112

o They have a polar phosphate group which is hydrophilic and faces the aqueous solution so outside o Fatty acid tails are non-polar and move away from an aqueous environment so are inside o Both tissue fluid and cytoplasm is aqueous so phospholipids firm 2 layers with hydrophobic tails facing inward attracting each other and phosphate group facing outwards interacting with aqueous environment proteins which can move freely and are randomly distributed

Answer 113

o Glycoproteins are involved in cell adhesion for aggregating cells into tight junctions in tissues. They also act as receptors for chemical signals (cell signalling). When the chemical binds to the receptor it causes a response from the cell provoking a direct response or a cascade of events o Glycolipids act as cell identity markers or antigens allowing immune system to recognise them as self or non self Also help with stability by forming hydrogen bonds with surrounding water molecules but can be receptors sometimes o Cholesterol regulates fluidity of membrane- high temps make the membrane less fluid and at low ones maintains fluidity. Is a lipid with a hydrophilic and phobic end interacting with philic and phobic ends respectively. It stops the phospholipid molecules grouping together and crystallising, by partially immobilising nearby phospholipids o Intrinsic proteins have amino acids with hydrophobic R groups keeping them in place by interacting with the hydrophobic core - channel and carrier. They span the entire phospholipid bilayer and are free to move about so have a random arrangement o Extrinsic proteins have hydrophilic R groups on outer surfaces to interact with polar heads of phospholipids or with intrinsic proteins. Can move between layers. o Channel proteins allow the movement of large or hydrophilic molecules to diffuse by providing a hydrophilic channel e.g. Glucose. They can be gated and are passive o A variety of carrier proteins allow for the controlled movement of substance through the membrane using both passive diffusion or active transport- ATP. They have specific shapes for certain molecules, and then the protein changes shape to allow molecules through. Usually for polar molecules. Can be denatured. o Receptor proteins can act as binding sites for hormones and other substances and can transmit the information to the interior of the cell.

Answer 114

o Polar molecules need channel proteins to enable them to pass through the membrane as they can’t get through the hydrophobic surface of the bilayer as they are not fat soluble o Non polar molecules diffuse/dissolve through the phospholipid bilayer eg. Steroid hormones

Answer 115

o Cell membranes are given kinetic energy when they get hot, so they vibrate o Lipids become more fluid so membranes become more fragile o Proteins are formed of coiled and folded strings of amino acids, held together by hydrogen bonds and disulphide bridges. When they get hot they untangle and break apart due to the vibrations, forming holes that destroy the structure, and the inner pigment/ cytosol can spill out as vacuole is damaged. o Carrier and channel proteins will be denatured at higher temperatures which also affects membrane permeability

Answer 116

o Slightly polar organic solvents like alcohol can denature the membrane, but weaker ones such as drinks wont dissolve the membrane but cause damage. Combination of alcohol and higher temperature can dissolve lipids. o Nonpolar alcohol molecules can enter the cell membrane and the presence of these molecules between the phospholipids disrupts the membrane

Answer 117

o Non polar signals can diffuse through the phospholipid bilayer and bind to intracellular receptors. Steroid hormones are fat soluble EG. testosterone o Polar signals must bind to membrane bound receptors (intrinsic proteins)

Answer 118

o Chemical messengers transported in the blood o Target cells are any cells with a receptor for that hormone o Hormone and receptor on target cell bind due to their complementary shape o Binding causes the target cell to respond in a certain way 1) The change in the receptor may cause the release of a second messenger inside the cell 2) The change in the target cell may result in an opening of a protein channel that was previously closed, or close one that was open 3) The change may activate an enzyme within the cell, or the membrane protein itself may be an enzyme itself which is activated EG. Insulin o Under normal circumstances there are some glucose channel proteins present, and some being held in vesicles inside the cell o When blood glucose levels rise the hormone insulin is secreted into the blood by the Pancreas o The insulin binds to its complementary receptor in the glycocalyx of target cells (liver, muscles) o This sets off a series of events that causes the vesicles to fuse with the cell surface membrane o This means many more glucose channel proteins are on the surface so there’s a greater uptake of glucose from the blood into the cell o The insulin hormone is then broken down and vesicles reform by pinching off from the plasma membrane reducing number of glucose pores to normal level Glucose is big and hydrophilic, so channel proteins are specific

Answer 119

o Eg. Beta blockers block receptors and prevent the heart from increasing the heart rate when it could be dangerous for patient o EG. For schizophrenia drugs mimic natural neurotransmitters that patients cannot produce o Viruses on the other hand enter cells by binding with receptors on cells plasma membrane EG HIV can enter cells of the immune system (T lymphocytes) which can prevent cells doing there job and may destroy the cell o Botox uses a toxin from a bacteria which binds with receptors on muscle fibres and prevents them from working causing paralysis

Answer 120

the overall movement of atoms or molecules from an area of higher concentration to an area of lower concentration, though phospholipid bilayer not through channel/carrier proteins. molecules move randomly as have kinetic energy to bump into other particles - Brownian motion move both ways but majority 1 way passive oxygen into red blood cells

Answer 121

o Other very small charged particles like water (polar) and small ions (calcium, sodium, potassium) can also diffuse directly through the lipid bilayer. (for nerve cells) but at slower rates o Larger or charged particles like glucose or amino acids are unable to pass through the lipid bilayer, and so must pass through membrane proteins to cross the membrane. This is known as FACILITATED DIFFUSION. It is still passive as the molecules are moving from an area of high concentration to an area of low concentration down a concentration gradient. This is because the hydrophobic interior or the membrane repels substances with charges.

Answer 122

o Rate is also affected by how many channel proteins are present Channel proteins: o Pores in the membrane with a specific shape that only allow a certain shaped ion or small polar molecule through. They can also be gated, so they can open or close. o Passive o They can limit a reaction o EG. Glucose into blood to cells Carrier proteins: o Specific shape so that only a certain (usually larger) molecule fits into it at the membrane surface. The molecule binding causes a change in shape of the protein that delivers the molecule to the other side of the membrane. o Active or passive Control: o Different membranes have different carrier and channel proteins in them, allowing a measure of control over what enters and leaves the cell. o NET diffusion will stop when there are an equal number of one type of particle on one side of the membrane as on the other. NB. This does NOT mean diffusion STOPS, but that molecules are entering at the same rate as they are leaving.

Answer 123

Temperature- the higher the temperature the higher the rate of diffusion as particles have more kinetic energy and move at higher speeds Conc. Gradient- the greater the difference in concentration the faster the rate as the overall movement will be larger. Stirring/ moving- provides kinetic energy SA- the larger the exchange surfaces the higher rate as more particles can interact at once and more likely to collide. Distance/ thickness- thinner means higher rate as takes less time to cross Size of molecule – small diffuses fastest

Answer 124

o Against a concentration gradient o Carried out by carrier proteins o Adenosine triphosphate (ATP) provides energy, which is generated by mitochondria in aerobic transpiration o If cells are deprived of oxygen then there is less ATP so active transport slows o Each carrier is specific to a certain substance/ substance o They can be involved in 2-way active transport – pump 1 in and 1 out at same time o Faster, allows accumulation o Inhibitors are usually to do with active transport o EG. Ions from soil to root hair cells – ions can diffuse through bilayer as they are small even though they are polar

Answer 125

1. The molecule or ion to be transported binds to receptors in the channel of the carrier protein on the outside if the cell- complementary shape 2. On the inside of the cell, ATP binds to the carrier protein and is hydrolysed into ADP and phosphate 3. Binding of the phosphate molecule to the carrier protein causes the protein to change shape opening up to the inside of the cell 4. The molecule or ion is released into the cell 5. The phosphate molecule is released from the carrier protein and recombines with ADP to form ATP 6. The carrier protein returns to original shape

Answer 126

o Primary is when ATP is directly used for the energy to transport molecules o Secondary is when energy is stored in a concentration gradient and the transport of one molecule is coupled to the transport of another down its concentration gradient and ATP is not directly involved in the transport process

Answer 127

o A form of active transport so requires ATP o Large molecules like enzymes, hormones and whole cells like bacteria are too large to move through channel or carrier proteins so are moved into and out of cell by bulk transport o Endocytosis- the bulk transport of material into cells o The 2 types are phagocytosis for solids and pinocytosis for liquids o The cell surface membrane invaginates when it comes into contact with the material to be transported. The membrane enfolds the material until eventually the membrane fuses, forming a vesicle. The vesicle pinches off and moves into the cytoplasm to transfer material for further processing within the cell- e.g. vesicles containing bacteria are taken to lysosomes where its digested by enzymes. o Some endocytosis is receptor mediated and is triggered when receptor proteins on the extracellular surface bind to specific substances o Exocytosis is where vesicles usually formed by the Golgi apparatus move towards and fuse with the cell surface membrane releasing the contents of the vesicle outside of the cell o Energy from ATP is needed for the movement of vesicles along the cytoskeleton, changing the shape of cells to engulf materials and fusion of cell membranes as vesicles form or as they meet the cell surface membrane. o Endocytosis and exocytosis can occur because the membrane is fluid so it can break and form allowing vesicles to form and break off o Examples: hormones like insulin released into blood by pancreatic cells pinocytosis: Microvilli in the gut use this process to absorb nutrients from food Phagocytosis: Uptake of lipoproteins by mammalian cells Foreign material and cell debris by neutrophils and macrophages o Plant cell vesicles carry materials to make cell wall o WBC phagocytes engulfing foreign invaders and fusion with lysosomes

Answer 128

Osmosis is the net movement of WATER particles from an area of high Ψ to an area of low Ψ by diffusion, across a partially permeable membrane. EG: water into root hair cells

Answer 129

o The amount of ‘free’ water molecules in a solution. o Pure water has the highest water potential, as all its water molecules are free to move. The Ψ of pure water = 0 kPa o Water potential is the pressure exerted by water molecules as they collide with the membrane or container measure in Pa or kPa o When substances dissolve in water, the water molecules cluster around the solute particles and are no longer free to move, so don’t count in water potential. The water potential has decreased i.e. it gets more negative. o The smaller the number (bigger no. before the -) the more concentrated, so the higher water pot. Will be the lower number before the - o Continues till reaches equilibrium- no net movement

Answer 130

o Animal cells burst in hypotonic- high water pot as they have thin (7nm) cell surface membrane and no cell walls so cant stretch or withstand the pressure increase. It will break and burst- lysis. o Crenation in hypertonic – low water pot. o Animal cells must therefore be bathed in a solution having the same osmotic strength as their cytoplasm. o We therefore need kidneys to regulate the amount of salt and water in our blood, under the control of our hypothalamus- this regulation process is called osmoregulation o Animals that live on dry land and salty sea water must conserve water but animals living in fresh water must get rid of excess water as fast as it gets in by osmosis

Answer 131

o Plants can’t control the water pot of the fluid around them e.g. roots are usually surrounded by pure water o When water enters the increased hydrostatic pressure pushes the membrane against the rigid cells walls – turgor pressure which resists the entry of more water and it becomes turgid. This provides support for plants that aren’t woody – prevents wilting o During plasmolysis, cells can die as the cytoplasm pulls away from the cell wall. The incipient point is where the cell membrane just begins to move away from the cell wall. It is assumed this is when 50% of the cells have been plasmolysed. o Flaccid is when the cell is not turgid but not yet plasmolysed. Plasmolysis is irreversible.  If you define hypertonic, isotonic or hypotonic, you must define them in terms of water pot.  The increase in pressure caused by the movement of water into a fixed volume is called hydrostatic pressure measured in kPa

Answer 132

o Transmembrane proteins that use energy to move ions and some molecules across a membrane across their concentration gradient proton pump: ATP is used to remove hydrogen ions from inside the cell to the outside, creating a large difference in proton conc. either side of the membrane, with the inside being very negative. This potential difference can be coupled to the transport of other molecules. Sodium potassium pump: A specific protein in the membrane that uses ATP to exchange sodium ions for potassium ions across the membrane. The large conc. difference can be used to drive the transport of other substances like glucose. Cotransport-sodium-glucose symport: A gradient in sodium ions drives the active transport of glucose in intestinal epithelial cells. The specific transport protein couples the return of sodium ions down its conc. gradient with the transport of glucose into the intestinal epithelial cell. The low intracellular conc. of sodium is maintained by the sodium potassium pump.

Answer 133

o Enzymes are very specific catalysts made by cells that catalyse (speed up) metabolic reactions without undergoing permanent change so it can be used again o In small quantities they reduce the need for high pressures, temperatures and extreme pH as well as high concentrations of reactants which would kill organisms. need water as need aqueous solution for movement of enzymes and substrates o Reactions that enzymes catalyse are reversible. Enzymes don’t determine the direction if the reaction, only the speed o Enzymes are globular proteins with complex tertiary structures. Some are single polypeptides, and some have 2 or more polypeptides so have quaternary structure o Enzymes form the biological molecules that make up living tissues and break down the biological molecules that provide organisms with energy and building materials EG. Polymers like cellulose forms the cell walls of plant cells and long protein molecules form the contractile filaments of muscles in animals. Different cell components are synthesised and assembled into cells, tissues, organs and organisms. Anabolic reactions needed form growth are catalysed by enzymes - structure o EG. Cells in the organs in the abdomens of fireflies make the enzyme luciferase. They also make luciferin, the only substrate to it can catalyse. When cells are stimulated by nerve impulses to release luciferin, which is broken down un the presence of ATP bound to magnesium ions. The reaction releases light. Energy is realised from large organic molecules like glucose in metabolic pathways consisting if many catabolic reactions catalysed by enzymes - function

Answer 134

o Performs its function within the cell that produces it o Many reactions that occur simultaneously inside cells at low temperatures, low concentrations and pH 7 are catalysed by intracellular enzymes o Some are free in the cytosol, nucleoplasm, mitochondrial matrix and stroma, others are fixed in place, like either side of cell surface membrane and inner membrane in mitochondria and chloroplasts. EG. Sucrase is an enzyme of the digestive system and is fixed to the cell membrane of cells lining the gut EG. Catalase acts on hydrogen peroxide, a waste product of metabolic processes in cells that is a powerful oxidising agent so very toxic. It breaks it down to oxygen and water in seconds, compared to the months it would take to degrade by itself, found in plants and animals. Some cells use hydrogen peroxide to kill pathogens, cells infected with viruses and cancer cells

Answer 135

o An enzyme that functions outside the cell which it originates o Substrates are raw materials and found in diet or environment o Catalyse reactions that occur out of cells like those involved in breakdown of food In the gut, as large molecules cannot be absorbed unless broken down into small ones o Many digestive enzymes are secreted from the cells that make them into the gut lumen EG. Amylase hydrolyses starch to maltose in mouth and pancreas in saliva and pancreatic juice. Maltase then breaks down maltose into glucose in the small intestine. Glucose can be absorbed by cells lining digestive system into bloodstream. 2 enzymes are needed as each is specific to a reaction. EG. Trypsin is a protease which breaks down protein molecules into peptides and then can be further broken into amino acids by other proteases. Released by pancreas into small intestine. Again can be absorbed into blood. EG. Some organisms rely entirely on extracellular digestion where the enzymes are secreted outside their body to digest food, like single celled organisms. Fungal hyphae secrete the enzymes onto the food then absorb the simple molecules through hyphal walls.

Answer 136

o Proposed in 1890 o The idea of the substrate fitting exactly into the active site o The active site is an area within the tertiary structure of the enzyme o The substrate acts as the key fitting into the lock of the active site of the enzyme o Interactions between the R groups within the active site and the substrate stabilise the enzyme substrate complex o The substrate is held so that the right atom groups are close enough to react o The R groups within the active site of the enzyme will also interact with the substrate forming temporary bonds which put strain on the bonds with the substrate helping the reaction along o The substrate is altered and forms a product forming an enzyme product complex o The enzyme is unchanged so releases the substrate and is a free enzyme molecule ready to accept another substrate molecule

Answer 137

o Proposed in 1959 o The lock and key theory doesn’t explain how the substrate and enzyme are able to collide successfully to form he enzyme substrate complex o As collisions are so random, it would be hard for them to collide to form the complex if the active site were a fixed shape o Proteins are not fixed structures like the other theory suggests o The active site doesn’t have a complementary shape to the substrate until it has moulded around the substrate so the 2 fit closely together and the amino acids with specific r groups within the active site are close to the substrate holding it together. The initial interaction between the enzyme and substrate is by weak chemical bonds, but they rapidly induce changes in the enzymes tertiary structure (active site) that strengthen bonding putting strain on the substrate molecule bonds so it breaks/makes bonds and creates the product(s) (break or make depends if catabolic-respiration or anabolic-photosynthesis) o This can weaken a particular bond or bonds in the substrate therefore lowering the activation energy for the reaction as les energy is required to overcome the bonds

Answer 138

o Active sites determine the specificity of an enzyme o The active site is a specific shape complementary to a substrate or part of a substrate, allowing a complementary fit o Active sites are groves or clefts, composed of as small number of amino acids within a polypeptide o The features of the active site and the type of substrate it accepts are dependent on the r groups of the amino acids o R groups can no polar which provides a hydrophobic interior to the active site accepting non-polar substrates o R groups can also be polar which means they form temporary ionic bonds with substrate molecules o Specificity comes in different degrees- either for 1 reaction or for a few of the same type or act on a particular linkage EG. Protease acts on peptide bonds

Answer 139

o Reactions that occur in organisms involve compounds that are very stable o There is an energy barrier that prevents a chemical reaction happening or only allows it to happen very slowly o EG. Hydrogen peroxide takes 6 months to decompose due to the amount of kinetic energy it has to build up. o Activation energy is the amount of energy required to overcome the barrier o This can be done by increasing temperature and or pressure or by adding a catalyst o Enzymes don’t lower the overall energy change of the reaction, they provide an alternative pathway with a lower activation energy o This allows reactions to occur without the extreme conditions that could kill cells o Once the enzyme substrate complex is formed, the activation energy is lowered as a different reaction pathway is followed. The energy of the substrate and product stay the same o This is possibly due to the tensions formed within the complex by the charges within the amino acids at the active site and the links between the amino acids and the substrate

Answer 140

o Some enzymes are inactive until they combine with a non protein substance that changes their tertiary structure to that their active site is able to bind with substrate molecules and ESC is catalysed/more likely to form. Ionic interactions and hydrogen bonds can be affected by charges too. This is a cofactor. o Some enzymes require inorganic ions to function which stabilise the enzyme structure or take part in the reaction at the active site EG. Amylases digests starch into maltose, require the presence of calcium ions and chloride ions to function correctly and form correct active site shape obtained via diet

Answer 141

o Larger organic cofactors are called coenzymes. o Some of these are bound permanently to the enzyme often in or near the active site. Others only bind temporarily to the active site during the reaction. o Many of the B groups of vitamins are used to make important coenzymes in metabolic reactions: Pantothenic acid or B5 is a component of coenzyme A Nicotinic acid or B3 is used in the synthesis of the coenzymes NAD and NADP The coenzyme FAD is based on vitamin B1- riboflavin o NAD and FAD are alternatively reduced and oxidised in the reactions of which they take part, which transfers energy in the form of hydrogen ions in respiration o NADP does a similar thing in chloroplasts during photosynthesis o Other coenzymes like ATP and coenzyme A transfer chemical groups, ATP transferring phosphate groups between respiration and energy consuming processes in cells o coenzyme A transfers the acetyl group (-CH3CO) from glucose and fatty acids during respiration. (breaks down fatty acids and carbs)

Answer 142

o Prosthetic groups are when any cofactor becomes a permanent part of an enzyme- tightly bound o These contribute to the 3D shape of the enzyme so are vital for its ability to function o Carbonic anhydrase, an enzyme found in red blood cells is important in the conversion of CO2 and water into carbonic acid (metabolism of CO2) o Its prosthetic groups is a zinc 2+ ion that forms an important part of its active site

Answer 143

o Many enzymes are produced in an inactive form, known as inactive precursor enzymes, particularly enzymes that cause damage within cells producing them or to tissues where they are released, or whose action needs to be controlled and only activated under certain conditions o Precursor enzymes often need to undergo change in shape (tertiary structure) to be activated o This can be done by adding a cofactor o Before the cofactor is added, the precursor is called an apoenzyme o When the cofactor is added its activated its called a holoenzyme o This can be brought about by the action of another enzyme like protease which cleaves certain bonds in the molecule o A change in conditions can also cause a change in tertiary structure and activates a precursor enzyme- these types are called zymogens or proenzymes o EG. When inactive pepsinogen is released into the stomach to digest proteins, the acid pH brings about the transformation into the active enzyme pepsin, protecting body tissues against the digestive action of pepsin

Answer 144

o Molecules in solution move randomly and continuously, colliding with each other (Brownian Motion) 1. Low temperatures so less kinetic energy so molecules move slower and collide with less force, so lower frequency of successful collisions (enough activation energy) so less ESC formed so less product and slower rate of reaction. 2. Increasing temperature so more kinetic energy and increasing frequency of successful collisions so more ESC formed so more product (EPC) and increasing rate of reaction 3. This is the optimum where all the active sites are occupied (unless lack of substrates). This is the highest temperature before they denature and they have the most kinetic energy, and the highest frequency of successful collisions (with enough AE), with the most ESC formed and the most/ more product with the fastest rate of reaction. Usually between 35-40 for humans and mammals, 20 for plants and 80 for bacteria, which have thermostable/philic enzymes. Psychrophilic organisms live in very cold areas and can have optimums of 5. 4. Hydrogen bonds and ionic bonds in the tertiary structure break first as the heat vibrates the molecules as they have more KE straining the bonds, so the 3D shape of the active site changes so is no longer specific/ complementary to substrate so can’t form ESC and is permanently denatured, ROR decreases rapidly and reaction stops. Usually higher than 60 but can depend how long they are left in the heat for.

Answer 145

o Enzymes adapted for the cold tend to have more flexible structures like the active site, making them less stable than enzymes that work at high temperatures. Smaller temperature changes will denature them. o Thermophiles are adapted to live in hot environments and are more stable than other enzymes due to more bonds, like hydrogen bonds and sulphur bridges, in their tertiary structures. The active sites and shapes are more resistant to change as temp rises.

Answer 146

burst phase

Answer 147

the start because the concentration of substrate molecules is higher at the start so there is more chance they will enter the active site

Answer 148

o Between 0oC and 40oC any change in tissue temp causes problems for animals o Most biochemical reactions are temp sensitive o The sensitivity is described by the temperature quotient or coeffient Q10 o The Q10 is a measure of the rate of change of a biological or chemical system as a consequence of increasing the temperature by 10°C. o A temperature increase of 10⁰C is equal to the Q₁₀ coefficient for that enzyme and can be used to compare the rate of reaction for different enzymes. o It is calculated by dividing the rate of reaction at a certain temp by the rate of reaction of the same enzyme at a temp 10oC lower o Q10 = RT/RT-10 o If a reaction is not temp sensitive, it has a Q10 of 1 o Most biological Q10 values are between 2 and 3 o A Q10 of 2 means that for every 10oC rise in temperature the rate of reaction doubles and for a value of 3 it triples o So the larger the Q10 the faster the rate of a reaction rises in response to a temperature increase o The graph produced is a curve o If there is no scale for ROR you can calculate Q10 by measuring distances using a ruler and using these as equivalent to rates

Answer 149

o pH is a measure of H+ ion concentration. (H must be small at top) o it’s a logarithmic scale so a change in 1 pH unit is x10 in conc. Of hydrogen ions o The higher the H+ concentration the lower the pH (acidic) o The H+ ions can disrupt the bonding, so active site is less effective o Ionic interactions and H bonds are primarily affected between R groups of amino acids in the active site o The active site will only be the right shape at a certain hydrogen ion concentration – optimum o In the induced fit model, the charges allow the substrate to enter and become linked with the active site allowing the enzyme substrate complex to form. Changes in the charge therefore effect the ability of the active site to successfully link with the substrate. o pH range can be wide or narrow, and optimums vary EG. Pepsin stomach acid or Trypsin alkaline small intestine or urease catalyses the hydrolysis if urease at neutral o a control for a reaction investigating the effect of pH on enzyme ROR would be no enzyme

Answer 150

neutral, saliva, starch to maltose acidic (1-2), gastric juice in stomach, protein to polypeptide alkaline (8), pancreatic juice in small intestine, proteins to polypeptides triglycerides to glycerol and fatty acids amylase, starch to maltose maltase, maltose to glucose o most intracellular enzymes have an optimum of 6.5 which is the pH of cytosol o lysosomal enzymes have a lower optimum so rarely function if released into cytosol o Buffer solutions can maintain different values of pH

Answer 151

1- The optimum o The solution contains the ideal no. of H+ ions. o The ionic bonding of the enzyme is not disrupted. o The shape of the active site is not changed it is specific and complementary o Substrate fits forming ESC then EPC o Product is released o Rate of reaction is at its maximum 2- Either side of the optimum o Change in pH either side of the optimum provides less/more H+ ions o Ionic bonding is disrupted changing the tertiary protein structure o Active site changes its 3D shape so it is no longer specific and complementary o the substrate no longer fits o Less or no ESC are formed o So less or no product formed o Mild pH change effects are reversible o Extreme pH can cause irreversible denaturation

Answer 152

o For a fixed enzyme concentration, the rate of reaction increases with increasing substrate concentration. o An increase in the number of substrate molecules results in an increase in the frequency of successful collisions between enzyme and substrate molecules. o More ESC will be formed. o Rate of reaction increases. o The rate of reaction is limited by substrate concentration. o The rate of reaction continues to increase (directly proportional) with increases in substrate concentration. o a point is reached when further increase in substrate concentration no longer produces a significant change in the rate of reaction. o The active sites of all the enzyme molecules are saturated with substrate molecules. o Any extra substrate molecule has to wait until the ESC has released the products before it can enter the active site of the enzyme. o The rate of reaction is now limited by enzyme concentration, and can only proceed at the enzyme turnover rate.

Answer 153

o If the substrate concentration is maintained at a high level and other conditions such as temperature and pH are kept constant, the rate of reaction is proportional to the enzyme concentration o As enzyme concentration increases, the frequency of successful collisions between the enzyme and substrate molecules increases. o More ESC are formed o The rate of reaction increases. o At very high enzyme concentrations, if the concentration of substrate molecules is limiting, an increase in enzyme concentration would not result in any further increase in the rate of reaction.

Answer 154

o Molecule or part of a molecule that is structurally similar to the substrate and compete with substrate for active site- enters into, binds or blocks it preventing ESC forming o Can still reach v max but may take longer, if the substrate is increased so much more than the inhibitor o Temporary o The inhibitor competes with the substrate to occupy the active site, so the substrate can’t bind. The higher the inhibitor concentration the less likely the ESC will form so the slower the rate of reaction, but doesn’t change the v max o The inhibitor doesn’t have to be exactly the same shape as the substrate o Statins inhibit an enzyme used in the synthesis of cholesterol. They are prescribed to help people reduce cholesterol levels in blood, to prevent heart disease o Aspirin irreversibly inhibits the active site of COX enzymes, preventing the synthesis of prostaglandins and thromboxane, the chemicals for producing pain and fever.

Answer 155

o The enzyme binds to an allosteric site which changes the 3D tertiary shape (conformation) of the active site preventing it from catalysing a reaction as it is no longer complementary to the substrate o This means a proportion of the enzyme molecules are out of action so the effective enzyme concentration is decreased o Can be permanent and not leave but some are reversible o The inhibitors have no structural resemblance to the substrates o Cofactors also bind to an allosteric site o You can also have allosteric activators which bind to activator sites to change the shape of an enzyme so that the substrate fits (cofactor) o Reaction hasn’t stopped so some will be reversible but doesn’t reach v max as others are irreversible o EG. Organophosphates used in insecticides and herbicides irreversibly inhibit the enzyme acetyl cholinesterase, an enzyme necessary for nerve impulse transmission, leading to muscle cramps, paralysis and death o EG. Proton pump inhibitors are used to treat long term indigestion as they irreversibly block an enzyme system responsible for secreting hydrogen ions into the stomach, preventing excess acid which can lead to stomach ulcers

Answer 156

o Enzymes must be controlled otherwise can be fatal EG. In multiple sclerosis the immune system starts destroying nerves by allowing destructive enzymes to attack nerve cells, often resulting in paralysis o Many poisons work by inhibiting the action of enzymes involved in metabolic processes E.g. Potassium Cyanide is an irreversible inhibitor of the enzyme Cytochrome C Oxidase, used in respiration reactions in cells. It forms strong covalent bonds with the enzyme. The only way to reverse the inhibition is to make new enzymes, which takes time. Is a metabolic poison as it prevents metabolic reactions occurring. o Some Enzyme Inhibitors can be used as Medicines o Infection by viruses can be treated by inhibitors to the viral enzyme Protease. This means that the viruses cant build new protein coats and so cant replicate. EG. Penicillin irreversibly inhibits a bacterial enzyme (transpeptidase) responsible for forming cross-links in bacteria cell walls halting reproduction.

Answer 157

When the end product of a metabolic pathway builds up and inhibits the first reaction as a non competitive inhibitor- negative feedback prevents excess product and waste as reaction controls itself EG.o Respiration is a metabolic pathway resulting in the production of AT. The 1st step involves the addition of 2 phosphate groups to a glucose molecule. The addition of the second phosphate group which results in the breakdown of the glucose molecule is catalysed by the enzyme phosphofructokinase (PEK). The enzyme is competitively inhibited by ATP, so it regulates its own production, so when ATP levels are high more ATP binds to the allosteric site on PEK

Answer 158

bound by a double nuclear membrane nuclear pores Chromosomes or chromatin- DNA wrapping around proteins called histones nucleolus which is a dense solid structure composed of nucleic acid and RNA RNA produces rRNA which is combined with proteins to form ribosomes contains coded genetic information in the form of DNA which provides the template for making RNA needed to make proteins so indirectly controls metabolic activities 10-20 um Diameter animals and plants

Answer 159

membrane bound organelles with a double membrane inner membrane folded into cristae creating larger SA fir enzymes used in aerobic respiration fluid interior is matrix contain own DNA with 70S ribosomes produce own enzymes and reproduce themselves resemble bacteria carry out final stages of aerobic respiration where ATP is produces- cytosol is anaerobic 1um diameter and 1um length. plants and animals metabolically active cells like muscle and nerve and liver

Answer 160

membrane bound organelles with a double outer membrane internal membranes form thylakoids, grouped into stacks called grant, joined by internal lamellae- thin flat pieces of thylakoid membrane chlorophyll pigments found in thylakoids thick fluid stroma is found in space between grand have own DNA and 70S ribosomes so can make own proteins starch granules found just outside where carbs are stored in amyloplasts grana contain green pigment chlorophyll which absorb light energy for photosynthesis 2 um diameter 10 um long plant cells

Answer 161

part of the endomembrane system containing ER and golgi network of membranes through cytoplasm enclosing a series of connected flattened sacs called cisternae these membranes join with outer nuclear membrane to form a continuous membrane ribosomes embedded in outer membrane the cells transport system ribosomes here make proteins destined for transport and secretion out of the cell 30-50nm diameter plants and animals pancreas and liver produce a lot of hormones and enzymes

Answer 162

long network of folded tube-like structures with no ribosomes makes and stores lipids like phospholipids for cell membranes and steroid hormones also makes and stores carbs contains enzymes that detoxify lipid-soluble drugs and some harmful products of metabolism 30-50nm diameter plants and animals liver produces lipids and steroid hormones

Answer 163

free in cytoplasm and and attached to RER membrane s made of ribsosomal ribonucleic acid and protein large subunit and small subunit which are separate and come together in protein synthesis 80S in eukaryotic not 70S to manufacture proteins my assembling aa if found in cytosol is use to make proteins withn the cell itself if found in RER makes proteins for usage outside cell (protein synthesis) 25nm plants and animals liver cells as protein synthesis occurs here

Answer 164

A series of membranous flattened sacs known as cisternae, separated from cytoplasm by a membrane. Similar to SER but the cisternae are not interconnected. There are 2 sections: the cis Golgi network and the trans Golgi network. vesicles delivered from RER join at cis face proteins and lipids are processed, packaged and transported. processed and modified in cis network then passed to trans network where they are packaged into vesicles ready for transport and secretion 2.5um animals and plants but fewer and larger in animals

Answer 165

a component of the cytoskeleton constructed of microtubules arranged in 9 triplets forming a cylinder occur in pairs near nucleus and form the centrosome Centrosomes help with formation and organisation of spindle fibres during cell division. 2 centrioles are found in each centrosome. Celiogenesis is the formation of cilia and flagella on the surface of cells, which help the cell move. Centrioles play a role in the positioning of these structures. 250nm length animal only

Answer 166

contain 40-50 hydrolytic enzymes acidic environment unlike neutral cytoplasm digest cellular material- food and foreign matter. may come from outside cell like bacteria or inside like damaged or old organelles part of immune system as break down pathogens ingested by phagocytic cells have a part in apoptosis 100nm animal cells liver, kidney, pancreas as have stuff to be broken down white blood cell lysosomes break down microorganisms acromosome in spr=erm to penetrate egg

Answer 167

membrane bound sac (tonoplast) within cytoplasm semi permeable membrane filled with solution of salts and sugars called cell sap in plants are large and provide structural support (turgor) store water, nutrients and waste and gets rid of them 1-10 um smaller and more and transient in animals

Answer 168

made of cellulose, a complex carb for plants and algae freely permeable fungal cells have wall of chitin which is pitted and composed of cellulose fibres to let water and dissolved substance through gives shape, supports and protects cell from pathogens and prevents is bursting when water flow in 5-20 nm thick plants

Answer 169

no centrioles of lysosomes no cell wall or chloroplasts the liquid part whereas cytoplasm includes organelles

Answer 170

1) High energy yield so acts as an important energy source to be respired 2) Act as an energy store- lipid droplets in plants and fat in adipose tissue in animals. Insoluble (don’t affect water potential of cell vital for storage of molecules) 3) Thermal insulation under skin of mammals 4) Electrical insulation around some nerve cells in vertebrates and some invertebrates as it’s a poor conductor of heat 5) Waxy cuticle around leaves and stems and waterproofing of birds feasthers 6) Forms biological membranes as are hydrophobic 7) Group of hormones called steroids are lipids 8) When oxidised during respiration, triglycerides release hydrogen molecules which combine with the oxygen to form metabolic water, relied on my desert animals to survive 9) Aids buoyancy so useful for aquatic animals like whales 10) Protection of vital organs

Answer 171

 Lipids are macromolecules (not polymers) as they are not formed of many similar monomer units.

Answer 172

 They dissolve in organic solvents like alcohol, but no in water- hydrophobic. This is because the electrons in their outer orbitals that form the bonds are more evenly distributed than in polar molecules no there are no positive or negative areas.

Answer 173

o When all the carbon atoms in a fatty acid are joined by single bonds o When combined with glycerol forms a saturated fat o Usually animal fatty acids such as stearic acid and butyric acid.

Answer 174

o Where the hydrocarbon chain has at least one double bond, forming a mono-unsaturated fatty acid. o When there are many double bonds it’s called a poly-unsaturated fatty acid (often in plants- oleic acid) o The double bond changes the shape of the hydrocarbon so that it kinks at the bond. o They hydrocarbon chains do not lie straight together and push apart, making unsaturated fatty acids liquid at room temperature so are oils.

Answer 175

o Formed by a condensation reaction between fatty acids and glycerol. o An ester bond is formed o The glycerol molecule is an alcohol o The fatty acid molecule is different depending on molecule of fat or oil formed- is a long molecule consisting of a hydrocarbon chain and a carboxyl group on the end- carboxylic acid o The carboxyl group reacts with the OH group of glycerol to form the ester bond in an esterification reaction o The methyl group(-CH3) at the other end makes the whole chain hydrophobic. o Because there are 3 -OH groups on the glycerol, 3 fatty acids bond to bond to three glycerol by 3 condensation reactions, so 3 molecules of water are lost and 3 ester bonds form in each for each triglyceride. o The chain is usually between 14 and 22 carbon atoms long

Answer 176

o Modified triglycerides containing carbon, hydrogen, oxygen and phosphorus. o Inorganic phosphate ions (PO4 3-) are found in the cytoplasm of every cell. o They have extra electrons so are negatively charged and soluble in water o One of the fatty acid chains in a triglyceride is replaced with a phosphate group o The phosphate group is usually attached to an nitrogen containing water soluble group like choline- creates a hydrophilic head o Form a layer on the surface of the water with phosphate heads in water and tails sticking out. They are called surface active agents or surfactants o Can also produce a bilayer (2 layered sheet formation) with tails pointing toward the centre of the sheet, protected from water by hydrophilic heads. o Form cell membranes due to bilayer arrangement. They can separate the aqueous environment which the cells usually exist from the aqueous cytosol within cells

Answer 177

o Lipids with a carbohydrate attatched by a glycosidic bond

Answer 178

Structure:A quaternary protein structure made from 4 polypeptides, 2 alpha, and 2 beta subunits, which create 2 alpha helixes and 2 beta pleated sheets. It is a conjugated protein, so contains a non-protein component called a prosthetic group (permanently attached to the molecule and is vital for the normal functioning of the molecule). Each subunit contains a prosthetic haem group, which contains iron II ions, which can combine with oxygen. Function: Transports oxygen around the body; picks up oxygen at the lungs and transports it to cells where it is needed for respiration and released.

Answer 179

Structure: It is a globular protein, with a quaternary structure. It is composed of 2 polypeptide chains with 21 amino acid residues in chain A and 30 amino acid residues in chain B. The chains are held together by 3 disulphide bridges in alpha helixes. Function: Hormone involved in the regulation of blood glucose concentration. Insulin’s solubility allows it to be dissolved and transported in the blood. The specific shape means that it fits into specific receptors on cell surface membranes.

Answer 180

Structure: Catalase is an enzyme and is a quaternary protein containing 4 haem prosthetic groups. Function: Catalase is an enzyme, so its main function is to speed up reactions, and its 3D structure means that it is specific to this particular reaction (active site): the iron II ions allow catalase to interact with hydrogen peroxide and speed up its break down, which is a common by-product of metabolism but can be damaging if it accumulates.

Answer 181

Structure: Have 3 polypeptide chains wound round each other in a triple helix structure to form a tough rope like protein. Every third amino acid in the polypeptide chain is glycine, which is a small amino acid, allowing 3 protein molecules to be closely packed in the triple helix. Hydrogen bonds form between the polypeptide chains forming long quaternary proteins with staggered ends, allowing proteins to join end to end forming long fibrils called tropocollagen. These fibrils cross link to produce strong fibres. Collagen also contains high amount of the amino acids proline and hydroxyproline, and the R groups in these repel each other adding to stability of collagen. Function: When multiple fibres of collagen create larger bundles, they are found in ligaments, tendons, heart, arteries, bone and cartilage providing strength and support, as well as in skin forming a mesh resistant to tearing. Also found in nervous system.

Answer 182

Structure: A quaternary protein made by linking many soluble tropoelastin protein molecules to make a very large insoluble and stable cross-linked structure. The multiple tropoelastin molecules aggregate through interactions between hydrophobic areas. The cross links are covalent bonds which involve the amino acid lysine. Tropoelastin molecules contain alternate hydrophobic and lysine rich areas. Function: A connective tissue able to stretch and recoil without breaking like small springs. Each elastin provides strength and elasticity to the skin and other tissues and organs in the body, such as walls of blood vessels and in the alveoli in lungs. They can therefore expand when needed but also return to their normal size.

Answer 183

Structure: Has lots of the sulphur containing amino acid- cysteine. It has lots of strong disulphide bridges forming strong, inflexible and insoluble materials. The amount of disulphide bond determines flexibility, so hair contains less and nails contain more Function: Found in hair, skin and nails

Answer 184

the number of phospholipids with unsaturated fatty acids in their tails unsaturated are bent so don't fit together as closely so is more fluid and allows proteins to move more easy

Answer 185

o As a mature red blood cell has no nucleus it can’t divide so new cells have to be constantly formed from multipotent stem cells in bone marrow to maintain erythrocyte count in blood