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A Level Biology OCR B (2022) > A Level Biology Definitions > Flashcards

A Level Biology Definitions Flashcards

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1
Q

action potential

A

A change in the electrical membrane potential which causes the transmission of a nerve impulse

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2
Q

activation energy

A

The energy that needs to be put in to cause a reaction. The activation energy is lowered by the presence of an enzyme (biological catalyst)

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3
Q

active immunity

A

A type of resistance developed in an organism through production of specific antibodies in response to an exposure to a pathogen (natural) or to a vaccine (artificial)

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4
Q

active site

A

A group of usually 3-12 amino acid R-groups that makes up a region on the surface of the enzyme into which a complementary substrate temporarily bonds to forming an enzyme-substrate complex

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5
Q

active transport

A

The movement of molecules from a region of low concentration to a region of high concentration against a concentration gradient requiring an input of ATP and involving transport proteins

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6
Q

acute disease

A

A disease that has a sudden onset and lasts a short time

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7
Q

adaptation

A

A trait that benefits an organism in its environment and increases its chances of survival and reproduction

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8
Q

adenosine triphosphate (ATP)

A

A phosphorylated nucleotide composed of a nitrogenous base (adenine), a pentose sugar, and three phosphate groups. The universal energy currency for cells

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9
Q

adhesion

A

The force of attraction between two different molecules e.g. water and molecule of lignin

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10
Q

adrenaline

A

A hormone secreted in response to stress

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11
Q

afferent

A

Leading towards or incoming (e.g. an afferent nerve or blood vessel is one that leads into a tissue or organ)

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12
Q

agglutination

A

The clumping together of antigen-bearing cells, microorganisms, or particles in the presence of specific antibodies

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13
Q

allele

A

A gene variant

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14
Q

alveoli

A

Small air sacs in the lungs which allow for rapid gaseous exchange

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15
Q

amino acid

A

An organic compound that has a central carbon atom to which an amine group (NH2) and carboxyl group (COOH) and variable residual group are attached. They are joined together by condensation reactions to form a polypeptide chain

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16
Q

amniocentesis

A

A procedure for sampling fetal cells from the amniotic fluid

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17
Q

anaphase

A

The stage of mitosis in which chromatids separate and are pulled towards opposite poles of the cell by the spindle

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18
Q

aneurysm

A

A localised bulge of an artery, vein, or the heart wall. The wall of the blood vessel or organ is weakened and may rupture

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19
Q

antenatal care

A

The care received by a pregnant woman

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20
Q

anther

A

The part of the plant that holds pollen

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21
Q

antibiotics

A

A substance produced by a living organism that kills or inhibits the growth of microorganisms, has no effect on viruses

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22
Q

antibodies

A

Globular protein molecules (immunoglobulins) produced by plasma cells (B lymphocytes) in response to stimulation by an antigen

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23
Q

anti-coagulant

A

A substance that prevents blood from clotting e.g. sodium citrate, heparin

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24
Q

anticodon

A

A sequence of three bases at the end of a tRNA molecule that allow complementary binding to a codon of the mRNA molecule being translated at the ribosome

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25
Q

antigen

A

A toxin or other foreign substance which induces an immune response in the body, especially the production of antibodies

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26
Q

antiparallel

A

A feature of the two strands in a DNA molecule. The 5’ (5 prime) end of one strand is directly opposite the 3’ (3 prime) end of the parallel strand. The two strands run in opposite directions

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27
Q

aorta

A

The major artery of the body, supplying oxygenated blood to the circulatory system

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28
Q

apoplast pathway

A

The transport route taken by water and dissolved substances through the cell walls and intercellular spaces of plants

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29
Q

apoptosis

A

Programmed cell death

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30
Q

artery

A

A thick-walled vessel that carries blood away from the heart

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31
Q

aseptic techniques

A

Any techniques/manipulations of equipment or materials that are designed to prevent contamination by microorganisms

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32
Q

asthma

A

A respiratory condition characterised by the inflammation and narrowing of the bronchi

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33
Q

atrio-ventricular node (AV node)

A

A patch of tissue in the septum of the heart that conducts the electrical stimulus from the atria in the heart through to the Purkyne fibres

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34
Q

atria

A

The upper chambers of the heart which receive blood returning from the organs and vessels of the body

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35
Q

autonomic nervous system

A

The branch of the motor nervous system that controls the non-conscious actions of the body. The autonomic system controls the actions of involuntary muscles and glands. Consists of two branches - the sympathetic and parasympathetic nervous systems

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36
Q

bacteriocidal

A

Describes a chemical substance that kills bacteria

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37
Q

bacteriostatic

A

Describes a chemical substance that prevents the reproduction of bacteria

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38
Q

Benedict’s test

A

A biochemical reaction to test for the presence of a reducing sugar, for example glucose. The test can be semi-quantitative of quantitative depending on the procedure used

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39
Q

benign

A

A tumour that stays in its original location and does not shed any cells into the blood plasma or lymph system

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40
Q

biodiversity

A

The variety of life, which can be measured on a genetic, species or ecosystem level

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41
Q

biosensor

A

A device which uses a living organism or biological molecules, especially enzymes or antibodies, to detect the presence of specific chemicals

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42
Q

biuret test

A

A biochemical reaction to test for the presence of proteins. It is qualitative test

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43
Q

blind trials

A

A clinical trial in which participants are unaware whether they are receiving a placebo or a medicinal drug

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44
Q

blood clot

A

A structure formed from fibrin fibres which traps red blood cells and platelets in response to the damage of a blood vessel

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45
Q

blood group

A

Also known as blood type - the classification of blood depending on which antigens are present on the plasma membrane of the erythrocytes

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46
Q

blood pressure

A

The force exerted by the blood against the walls of the blood vessels

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47
Q

B lymphocyte

A

A specialised leucocyte that is produced in the bone marrow and matures in the bone marrow. It forms plasma cells after contact with a specific antigen and produces antibodies

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48
Q

Bohr effect

A

Haemoglobin’s oxygen binding affinity is inversely related to the concentration of carbon dioxide and hence the acidity of the blood

  • an increase in blood CO2 concentration causes a decrease in blood pH which results in oxyhaemoglobin releasing oxygen
  • a decrease in carbon dioxide causes an increase in pH which results in haemoglobin picking up more oxygen
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49
Q

boosters

A

An additional dose of an immunising agent, such as a vaccine, given at a time after the initial dose to sustain the immune response elicited by the previous dose of the same agent

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50
Q

bradycardia

A

A slowness of the heartbeat, usually under 60 beats per minute in adults

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51
Q

broad-spectrum antibiotics

A

Antibiotics that are effective against a large variety of organisms

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52
Q

bronchi

A

The two main branches from the trachea that go into the lungs

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53
Q

bronchioles

A

One of the smaller subdivisions of the branched bronchial tree that connects the trachea to the alveoli

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54
Q

buffer

A

A chemical solution which has the ability to absorb or donate hydrogen ions (protons) to maintain the pH of the solution

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55
Q

bundle of His

A

Specialised cardiac muscle fibres that run from the atrioventricular node to the base of the heart

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56
Q

Calvin cycle

A

The reactions of the light-independent stage of photosynthesis

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57
Q

cancer

A

A disease usually caused by a mutation that causes uncontrolled cell division and the subsequent formation of a tumour. Some of these (primary tumour) cells may break away and be transported in the plasma or lymph system to form a secondary tumour in a different location

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58
Q

capillaries

A

Very small blood vessels where water, solutes, and respiratory gases are exchanged with body tissues

59
Q

capsid

A

The outer protein coat of a virus

60
Q

cardiac output

A

The amount of blood the heart pumps through the circulatory system in a minute

61
Q

carcinogen

A

A chemical or form of radiation that causes cancer

62
Q

cardiac monitor

A

A device for the continuous observation of cardiac function

63
Q

carrier protein

A

Protein found within a cell membrane that carries a specific molecule or ion across the membrane by active transport

64
Q

casparian strip

A

A band of impermeable suberin found in the walls of endodermal cells in plant roots

65
Q

catalyst

A

A substance that speeds up the rate of the reaction without itself being altered or used up in the chemical reaction

66
Q

cell cycle

A

The series of event that take place in a cell leading to its division to produce two daughter cells

67
Q

cell surface membrane

A

The phospholipid bilayer that forms the membrane surrounding the outside of a cell - sometimes known as the plasma membrane

68
Q

cellulose

A

A polysaccharide made from the condensation of many β-glucose molecules to form fribrils. It is used to form plant cell walls

69
Q

cell wall

A

A freely permeable structure lying outside of the cell surface membrane of plant, fungal, and bacterial cells

70
Q

centrifugation

A

The process of separating molecules and organelles on the basis of their density by spinning them at different speeds in a centrifuge

71
Q

centriole(s)

A

Two cylinders composed of microtubules which are involved in the process of mitosis and cell division in some eurykaryotic cells

72
Q

centromere

A

The region of a chromosome that joins two sister chromatids and attaches to spindle fibres during mitosis

73
Q

cerebellum

A

A structure located at the back of the brain in vertebrates, which coordinates and regulates muscle activity

74
Q

cerebrum

A

The largest part of the brain which is formed as two hemispheres

75
Q

channel protein

A

A protein pore that spans a cell membrane to enable water soluble molecules and small ions to passively cross the membrane

76
Q

chemotherapy

A

Destroying cancerous cells using drugs that affect cancerous cells more than other cells in the body

77
Q

chiasmata

A

The points at which crossing over occurs between homologous chromosomes

78
Q

chi-squared test

A

A statistical test that enables an investigator to determine whether differences exist between two sets of data

79
Q

chloroplast

A

The organelle in which photosynthesis occurs

80
Q

chordae tendinae

A

Also known as the heart strings, they are cord-like tendons that connect the papillary muscles to the tricuspid valve and the mitral valve in the heart

81
Q

chorionic villus sampling

A

A procedure for sampling fetal cells from the placenta

82
Q

chromatid

A

A DNA molecule; during prophase and metaphase of mitosis, a chromosome consists of two identical chromatids from the replication of DNA in S phase

83
Q

chromatography

A

A technique used to separate substances in a mixture according to differences in their solubility

84
Q

chromosome

A

A single DNA molecule, linear, and associated with proteins such as histones in eukaryotic cells

85
Q

chromosome mutation

A

A random change to the structure or number of chromosomes due to translocation or non-disjunction

86
Q

chronic disease

A

A disease that lasts a long time and has symptoms that worsen over time

87
Q

classification

A

The organisation of organisms into groups based on similarities in biochemistry, anatomy, behaviour and embryology

88
Q

climax community

A

The stable community of species that exists at the end of ecological succession

89
Q

clinical trials

A

A series of controlled studies in which a new medicinal drug is tested

90
Q

codominant

A

Alleles at a gene locus that are both expressed and therefore both contribute to the phenotype

91
Q

coenzyme

A

An organic non-protein molecule that binds temporarily with the substrate to the active site in order for an enzyme to function

92
Q

codon

A

A sequence of three bases on the template strand of the DNA or the mRNA that codes for one amino acid

93
Q

cofactor

A

A molecule or ion which aids the function of an enzymes - it can be an inorganic ion or a coenzyme

94
Q

cohesion

A

The attraction between water molecules due to hydrogen bonding

95
Q

cohesion-tension theory

A

A theory of intermolecular attraction that explains the process of water flow upwards (against the force of gravity) through the xylem of plants

96
Q

colony morphology

A

The characteristic of a bacterial colony, in cultures, in terms of shape, colour, edge and elevation

97
Q

colorimeter

A

A device that measures the absorbance of particular wavelengths of light by a specific solution, most commonly used to determine the concentration of a known solute in a given solution

98
Q

communicable

A

A disease or infection caused by microorganisms capable of being communicated or transmitted to another organism

99
Q

companion cells

A

A cell in the phloem tissue involved in actively loading sucrose into sieve tube elements. The companion cell is closely associated with the phloem sieve element, to which it is linked by many plasmodesmata

100
Q

compartmentalisation

A

The use of intracellular membranes to separate metabolic processes within the cell e.g. the nuclear envelope around the nucleus

101
Q

compensation point

A

The light intensity at which the rate of photosynthesis matches the rate of respiration

102
Q

competitive inhibitor

A

A molecule that has a similar shape to the natural substrate and which competes for the active site on the enzyme preventing the formation of enzymes substrate complexes and instead forming enzyme-inhibitor complexes

103
Q

complementary therapy

A

Treatments that involve procedures that are not part of mainstream medicine e.g. acupuncture, aromatherapy

104
Q

computed tomography (CT)

A

A radiographic technique that produces an image of a detailed cross section of tissue

105
Q

condensation reaction

A

A chemical process in which two molecules are combined to form a more complex molecule with the removal of a molecule of water to form a covalent bond

106
Q

correlation

A

The relationship between two variables e.g. a linear relationship

107
Q

co-transporter

A

Proteins in the cell surface membrane that allows movement of one molecule when linked to the movement of another molecule by active transport

108
Q

cotyledon

A

In seeds, the part of a plant embryo that becomes the first leaf

109
Q

countercurrent multiplier

A

Any mechanism that uses energy and countercurrent flow to establish concentration gradients

110
Q

cristae

A

Fold in inner membrane of mitochondria

111
Q

crossing over

A

The process in which homologous chromosomes exchange alleles during prophase I of meiosis

112
Q

cytokines

A

Cell signalling molecules which are used for communication between cells, allowing some cells to regulate the activity of others

113
Q

cytokinesis

A

The division of a cell to form two new cells

114
Q

cytoskeleton

A

A network of microtubules and microfilaments that give the cell shape and maintain its structure. They can attach to organelles and move organelles within the cytosol

115
Q

deamination

A

The removal of the amino group from an amino acid

116
Q

defibrillator

A

An apparatus used to control heart filbrillation by application of an electric current to the chest wall or heart

117
Q

deflection succession

A

The changes resulting from human activities (such as farming) that produce a stable community called a plagioclimax. A plagioclimax community and a climax community formed by natural, unimpeded succession have different compositions

118
Q

degenerate code

A

Situation where more than one codon codes for the same amino acid

119
Q

denaturation

A

Usually permanent change to the tertiary structure of a protein resulting in the loss of function. This can be caused by large changes in pH or high temperatures

120
Q

denitrification

A

The production of nitrogen gas from nitrates in the soil

121
Q

deoxyribonucleic acid (DNA)

A

The molecule responsible for the storage of genetic information

122
Q

depolarisation

A

The loss of the difference in charge between the inside and the outside of the plasma membrane of a muscle or nerve cell due to a change in permeability and migration of sodium ions to the interior

123
Q

diabetes mellitus

A

A condition in which a person cannot control blood glucose levels

124
Q

diaphragm

A

A sheet of muscular and fibrous tissue separating the chest cavity from the abdominal cavity. Plays an important role in ventilation

125
Q

diastole

A

Period of relaxation and repolarisation of the cardiac muscle when the chambers fill with blood

126
Q

dicotyledons

A

A plant that produces flowers and has two cotyledons (seed leaf) inside the seed, which develops wide leaves with veins

127
Q

differential staining

A

Staining processes that use more than one chemical stain, for example multiple stains can be used to distinguish between different microorganisms or structures/cellular components of a single organism

128
Q

differentiation

A

The development of unspecialised cells to form specialised cells

129
Q

diffusion

A

The movement of molecules down their concentration gradient as a result of random motion. In cells, diffusion may occur passively directly across the plasma membrane (simple) or via membrane proteins (facilicated)

130
Q

diploid

A

Cells that have two copies of each chromosome

131
Q

disaccharide

A

A dimer made from the condensation of two monosaccharides joined by a glucosidic bond

132
Q

disulfide bond

A

A S-S chemical bond between two sulfur atoms in the R group of two cysteine amino acids

133
Q

dominant

A

An allele that is expressed in the phenotype, the presence of which prevents a recessive allele from being expressed

134
Q

dopamine

A

Dopamine is a neurotransmitter (or chemical in the brain) that either increases or reduces the activity of neurons (nerve cells). A precursor to both adrenaline and noradrenaline

135
Q

double-blind trials

A

A clinical trial in which neither participants nor scientists are aware whether a placebo or medicinal drug has been issued

136
Q

double circulatory system

A

A type of blood circulation system in which the blood flows through the heart twice for each full circuit of the body

137
Q

ecosystem

A

The organisms and non-living components of a specific area, and their interactions

138
Q

efferent

A

Leading away from or outgoing (e.g. an efferent nerve or blood vessel is one that leads away from a tissue or organ

139
Q

electrocardiogram (ECG)

A

A graph showing the electrical activity in the heart during the cardiac cycle (heartbeat)

140
Q

electroencephalogram (EEG)

A

Technique where electrodes attached to the scalp detect small electrical impulses transmitted between brain cells. Impulses are recorded and monitored for abnormal readings

141
Q

electrolytes

A

Ions such as sodium, potassium, and chloride dissolved in water

142
Q

electron microscopes

A

A microscope that uses a beam of electrons to view a magnified image of an object giving it a greater resolution than a light microscope. There are two main types - scanning and transmission electron microscopes

143
Q

electron transport chain

A

A series of compounds that can transfer electrons from electron donors to electron acceptors via a series of redox reactions resulting in the transfer of protons (H+ ions) across a membrane and the generation an electrochemical proton gradient. This gradient drives the formation of ATP

A Level Biology OCR B (2022) (21 decks)

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