AQA Glossary Flashcards

Learn all the key definitions

1
Q

Definition

A

Key word

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2
Q

An ecological factor that makes up part of the non-biological environment of an organism

A

Abiotic

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3
Q

One of a group of chemicals called neurotransmitters released by neurones. It diffuses across the synapse between adjacent neurones and so passes an impulse from one neurone to another

A

Acetylcholine

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4
Q

Change that occurs in the electrical charge across the membrane of an axon when it is stimulated and a nerve impulse passes

A

Action potential

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5
Q

Filamentous protein which is involved in contraction within cells, especially muscle cells

A

Actin

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6
Q

Energy required to bring about a reaction. The _______ ________is lowered by the presence of enzymes

A

Activation energy

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7
Q

Resistance to disease resulting from the activities of an individual’s own immune system whereby an antigen induces plasma cells to produce antibodies

A

Active immunity

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8
Q

A group of amino acids that makes up the region of an enzyme into which the substrate fits in order to catalyse a reaction

A

Active site

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9
Q

Movement of a substance from a region where it is in a low concentration to a region where it is in a high concentration. The process requires the expenditure of metabolic energy

A

Active transport

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10
Q

A hormone produced by the adrenal glands in times of stress that prepared the body for an emergency

A

Adrenaline

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11
Q

Connective with the presence of free oxygen. Aerobic respiration requires free oxygen to release energy from glucose

A

Aerobic

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12
Q

One form of a gene

A

Allele

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13
Q

The number of times an allele occurs within the gene pool

A

Allele frequency

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14
Q

A normally harmless substance that causes the immune system to produce an immune response

A

Allergen

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15
Q

The response of the immune system to an allergen. E.g. hay fever

A

Allergy

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16
Q

Connected with the absence of oxygen. Anaerobic respiration releases energy from glucose or other foods without the presence of oxygen

A

Anaerobic

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17
Q

A substance produced by a living organism that can destroy or inhibit the growth of microorganisms

A

Antibiotic

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18
Q

The development in microorganisms of mechanisms that prevent antibiotics from killing them

A

Antibiotic resistance

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19
Q

A protein produced by lymphocytes in response to the presence of the appropriate antigen

A

Antibody

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20
Q

A sequence of three adjacent nucleotides on a molecule of transfer RNA that is complementary to a particular codon on a messenger RNA molecule

A

Anticodon

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21
Q

A molecule that triggers an immune response by lymphocytes

A

Antigen

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22
Q

A chemical which reduces or prevents oxidation. Often used as an additive to prolong the shelf-life of certain foods

A

Antioxidant

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23
Q

Route through the cell walls and intercellular spaces of plants by which water and dissolved substances are transported

A

Apoplastic pathway

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24
Q

Breeding of organisms by human selection of parents/gametes in order to perpetuate certain characteristics and/or eliminate others

A

Artificial selection

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25
Q

A chronic illness in which there is resistance to air flow to the alveoli of the lungs as a result of the airways becoming inflames due to an allergic response to an allergen

A

Asthma

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26
Q

Fatty deposits in the walls of arteries, often associated with high cholesterol levels in the blood

A

Atheroma

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27
Q

Nucleotide found in all living organisms, which is produced during respiration and is important in the transfer of energy

A

ATP (adenosine triphosphate)

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28
Q

Part of the nervous system, controlling the muscles and glands that are not under voluntary control

A

Autonomic nervous system

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29
Q

A process extending from a neurone that conductions action potentials away from the cell body

A

Axon

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30
Q

A type of white blood cell that is produced and matures within the bone marrow. They produce antibodies as part of their role in immunity

A

B cell ((B lymphocyte)

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31
Q

A simple biochemical reaction to detect the presence of reducing sugars

A

Benedict’s test

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32
Q

The range and variety of genes, species and habitats within a particular region

A

Biodiversity

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33
Q

The total mass of living material, normally measured in a specific area over a given period of time

A

Biomass

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34
Q

A simple biochemical reaction to detect the presence of protein

A

Biuret test

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35
Q

A person’s body mass in kilograms divided by the square of their height in metres

A

Body mass index (BMI)

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36
Q

A biochemical pathway that forms part of the light-independent reaction of photosynthesis, during which carbon dioxide is reduced to form carbohydrate

A

Calvin cycle

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37
Q

A disease, resulting from mutations, that leads to uncontrolled cell division and the eventual formation of a group of abnormal cells called a tumour

A

Cancer

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38
Q

A chemical, form of radiation or other agent that causes cancer

A

Carcinogen

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39
Q

A (continuous series of events which make up a single heartbeat

A

Cardiac cycle

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40
Q

A type of muscle found only in the heart, can contract continuously throughout life without stimulation by nerve impulses

A

Cardiac muscle

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41
Q

The total volume of blood that the heart can pump in each minute (stroke volume X heart rate)

A

Cardiac output

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42
Q

A protein on the surface of a cell that helps to transport molecules and ions across plasma membrane

A

Carrier molecule (carrier protein)

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43
Q

A distinctive band of suberin around the endodermal cells of a plant root that prevents water passing into xylem via the cell walls

A

Casparian strip

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44
Q

Process of separating out particles of different sizes and densities by spinning them at a high speed in a centrifuge

A

Centrifugation

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45
Q

Lipid that is an important component of cell-surface membranes

A

Cholesterol

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46
Q

An enzyme that breaks down and therefore inactivates the neurotransmitter acetylcholine in the synapse

A

Cholinesterase

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47
Q

One of the two copies of a chromosome that are joined together by a single centromere prior to cell division

A

Chromatid

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48
Q

A thread-like structure made of protein and DNA by which hereditary information is physically passed from one generation to the next

A

Chromosome

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49
Q

The organisms that make up the final stage of ecological succession

A

Climax community

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50
Q

A group of genetically identical organisms formed from a single parent as a result of asexual reproduction or by artificial means

A

Clone

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51
Q

Condition in which both alleles for one gene in a heterozygous organism contribute to the phenotype

A

Co-dominance

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52
Q

A sequence of three adjacent nucleotides in mRNA that codes for one amino acid

A

Codon

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53
Q

Attraction between molecules of the same type. It is important in the movement of water up a plant

A

Cohesion

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54
Q

Fibrous protein that is the main constituent of connective tissues

A

Collagen

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55
Q

All the living organisms present in an ecosystem at a given time

A

Community

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56
Q

DNA that is made from messenger RNA in a process that is the reverse of normal transcription

A

Complementary DNA

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57
Q

A chemical process in which two molecules combine to form a more complex one with the elimination of a simple substance, usually water

A

Condensation

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58
Q

The transfer of DNA from one cell to another by means of a thin tube between the two

A

Conjugation

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59
Q

Method of maintaining ecosystems and the living organisms that occupy them

A

Conservation

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60
Q

Variation in which organisms do not fall into distinct categories but show gradations from one extreme to the other

A

Continuous variation

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61
Q

Arteries that supply blood to the cardiac muscle of the heart

A

Coronary arteries

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62
Q

Any condition affecting the coronary arteries that supply heart muscle

A

Coronary heart disease (CHD)

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63
Q

When a change in one variable is reflected by a change in the second variable

A

Correlation

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64
Q

A mechanism by which the efficiency of exchange between two substances in increased by having them flowing in opposite directions

A

Countercurrent system

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65
Q

A type of chemical bond in which two atoms share a pair of electrons, one from each atom

A

Covalent bond

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66
Q

The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are exchanged

A

Crossing over

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67
Q

Exposed non-cellular outer layer of certain animals and the leaves of plants

A

Cuticle

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68
Q

Inherited disease in which the body produces abnormally thick mucus that obstructs breathing passages and prevents secretion of pancreatic enzymes

A

Cystic fibrosis

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69
Q

Term applied to plants that shed all their leaves together at one season

A

Deciduous

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70
Q

Permanent changes due to the unravelling of the three-dimensional structure of a protein as a result of factors such as changes in temperature

A

Denaturation

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71
Q

A process, usually branched, extending from the cell body of a neurone which conducts impulses towards the cell body

A

Dendrite

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72
Q

Bacteria that converts nitrates to nitrogen gas as part of the nitrogen cycle

A

Denitrifying bacteria

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73
Q

Temporary reversal of charges on the cell-surface membrane of a neurone that takes place when a nerve impulse is transmitted

A

Depolarisation

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74
Q

A metabolic disorder in which the body is unable to regulate the level of blood glucose

A

Diabetes

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75
Q

The stage in the cardiac cycle when the heart muscle relaxes

A

Diastole

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76
Q

Any member of the class of flowering plants called Dicotyledonae

A

Dicotyledonous plants

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77
Q

The process by which cells become specialised for different functions

A

Differentiation

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78
Q

The movement of molecules or ions form a region where there are in high concentration to one where their concentration is lower

A

Diffusion

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79
Q

Cells in which the nucleus contains two sets of chromosomes

A

Diploid

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80
Q

Variation shown when the characteristics of organisms fall into distinct categories

A

Discontinuous variation

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81
Q

An enzyme that acts on a specific region of the DNA molecule to break the hydrogen bonds between the bases causing the two strands to separate and expose the nucleotide bases in that region

A

DNA helicase

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82
Q

The process in which the double helix of a DNA molecule unwinds and each strand acts as a template on which a new strand is constructed

A

DNA replication

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83
Q

An allele that is always expressed in the phenotype of an organism

A

Dominant allele

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84
Q

All conditions and resources required for an organism to survive, reproduce and maintain a viable population

A

Ecological niche

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85
Q

More of less self-contained functional unit in ecology made up of all the interacting biotic and abiotic factors in a specific area

A

Ecosystem

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86
Q

An animal that uses the environment to regulate its body temperature

A

Ecothermic

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87
Q

An organ that responds to stimulation by a nerve impulse resulting in a change or response

A

Effector

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88
Q

Negatively charged sub-atomic particle that orbits the positively charged nucleus of all atoms

A

Electron

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89
Q

A chain of carrier molecules along which electrons pass, released energy in the form of ATP as they do so

A

Electron carrier molecule

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90
Q

A disease in which the walls of the alveoli break down, reducing the surface area for gaseous exchange, thereby causing breathlessness

A

Emphysema

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91
Q

An animal maintaining its body temperature by physiological mechanisms

A

Endotherm

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92
Q

A protein or RNA that acts as a catalyst and so alters the speed of a biochemical reaction

A

Enzyme

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93
Q

The study of the spread of disease and the factors that affect this spread

A

Epidemiology

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94
Q

A cell that has a membrane-bound nucleus and chromosomes

A

Eukaryotic cell

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95
Q

Consequence of an increase in nutrients, especially in nitrates and phosphates, in fresh water lakes and rivers, that often leads to a decrease in biodiversity

A

Eutrophication

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96
Q

Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across plasma membranes

A

Facilitated diffusion

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97
Q

Reproductive cell that fuses with another gamete during fertilisation

A

Gamete

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98
Q

A technique used to separate DNA fragments of different lengths by placing them on an agar gel and passing a voltage across them

A

Gel electrophoresis

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99
Q

A section of DNA on a chromosome coding for one or more polypeptide

A

Gene

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100
Q

The total number of alleles in a particular population at a specific time

A

Gene pool

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101
Q

A section of DNA that is used to indicate the location of a gene or other section of DNA

A

Gene marker

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102
Q

A mechanism by which genetic diseases may be cured by masking the effect of the defective gene by inserting a functional gene

A

Gene therapy

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103
Q

Depolarisation of the membrane of a receptor cell as a result of a stimulus

A

Generator potential

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104
Q

Organism that has had its DNA altered as a result of recombinant DNA technology

A

Genetically modified organism (GMO)

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105
Q

The genetic composition of an organism

A

Genotype

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106
Q

A hormone produced by α cells at the islets of Langerhans in the pancreas that increases blood glucose levels by initiating the breakdown of glycogen to glucose

A

Glucagon

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107
Q

The conversion of non-carbohydrate molecules into glucose

A

Gluconeogenesis

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108
Q

The conversion of glucose to glycogen

A

Glycogenesis

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109
Q

First part of cellular respiration in which glucose is broken down anaerobically in the cytoplasm to two molecules of pyruvate

A

Glyconeolysis

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110
Q

Substance made up of a carbohydrate molecule and a protein molecule

A

Glycoprotein

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111
Q

A stack of thylakoids in a chloroplast that resembles a pile of coins, this is the site of the light-dependent reaction of photosynthesis

A

Granum

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112
Q

Gases such as methane and carbon dioxide which in the atmosphere cause more heat energy to be trapped, so raising the temperature at the Earth’s surface

A

Greenhouse gas

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113
Q

One of a pair of cells that surround a stoma in plant leaves and controls its opening and closing

A

Guard cell

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114
Q

The place where an organism normally lives which is characterised by physical conditions and the types of other organisms present

A

Habitat

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115
Q

Globular protein in blood that readily combines with oxygen to transport it around the body

A

Haemoglobin

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116
Q

Cells that only contain a single copy of each chromosome

A

Haploid

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117
Q

Condition in which the alleles of a particular gene are different

A

Heterozygous

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118
Q

An inactive, dormant state, accompanied by a very low body temperature that certain animals go into during periods of prolonged cold

A

Hibernation

119
Q

A compound of protein and lipid molecules found in blood plasma, it transports cholesterol from other cells to the liver

A

High-density lipoprotein (HDL)

120
Q

Substance released on tissue injury that causes dilation of blood vessels

A

Histamine

121
Q

The maintenance of a more or less constant internal environment

A

Homeostasis

122
Q

A pair of chromosomes, one maternal and one paternal, that have the same gene loci and therefore determine the same features.

A

Homologous chromosomes

123
Q

Condition in which the alleles of a particular gene are identical

A

Homozygous

124
Q

The totality of the DNA sequences on the chromosomes of a single human cell

A

Human genome

125
Q

International scientific project to map the entire sequence of all the base pairs of the genes in a single human cell

A

Human genome project

126
Q

Chemical bond formed between the positive charge on a hydrogen atom and the negative charge on another atom of an adjacent molecule

A

Hydrogen bond

127
Q

The breaking down of large molecules into smaller ones by the addition of water molecules

A

Hydrolysis

128
Q

A condition that results from the core body temperature rising above normal

A

Hyperthermia

129
Q

Region of the brain adjoining the pituitary gland that acts as the control centre for the autonomic nervous system and regulates body temperature and fluid balance

A

Hypothalamus

130
Q

A condition that results from the core body temperature falling below normal

A

Hypothermia

131
Q

The means by which the body protects itself from infection

A

Immunity

132
Q

A hormone produced by the β cells of the islets of Langerhans in the pancreas which decreases blood glucose levels by increasing the rate of conversion of glucose to glycogen

A

Insulin

133
Q

Differences between organisms of different species

A

Interspecific variation

134
Q

Differences between organisms of the same species

A

Intraspecific variation

135
Q

Proteins of the cell-surface membrane that completely span the phospholipid bilayer from one side to the other

A

Intrinsic proteins

136
Q

Portions of DNA within a gene that do not code for a polypeptide

A

Introns

137
Q

An atom or group of atoms that has lost or gained one or more electrons

A

Ion

138
Q

A passage across a cell-surface membrane made up of a protein that spans the membrane and opens and closes to allow ions to pass in and out of the cell

A

Ion channel

139
Q

Groups of cells in the pancreas comprising large α cells, which produce the hormone glucagon, and small β cells, which produce the hormone insulin

A

Islets of Langerhans

140
Q

Solutions that possess the same concentration of solutes and therefore have the same water potential

A

Isotonic

141
Q

Variations of a chemical element that have the same number of protons and electrons but different numbers of neutrons

A

Isotope

142
Q

Refers to experiments carried out outside the living body, e.g. test tubes

A

In vitro

143
Q

Refers to experiments that are carried out within living bodies

A

In vivo

144
Q

Energy that an object possesses due to its motion

A

Kinetic energy

145
Q

Series of aerobic biochemical reactions in the matrix of the mitochondria of most eukaryotic cells by which energy is obtained through the oxidation of acetylcoenzyme A produced from the breakdown of glucose

A

Krebs cycle

146
Q

A tough, fibrous connective tissue rich in collagen that joins bone to bone

A

Ligament

147
Q

Stage of photosynthesis in which light energy is required to produce ATP and reduced NADP

A

Light-dependent reaction

148
Q

Stage of photosynthesis which does not require light energy directly but does need the products of the light-dependent reaction to reduce carbon dioxide and so form carbohydrate

A

Light-independent reaction

149
Q

A variable that limits the rate of a chemical reaction

A

Limiting factor

150
Q

The process linking glycolysis with the Krebs cycle in which hydrogen and carbon dioxide are removed from pyruvate to form acetylcoenzyme A in the matrix of the mitochondria

A

Link reaction

151
Q

The position of a gene on a chromosome/DNA molecule

A

Locus

152
Q

A compound containing both protein and lipid molecules that occurs in blood plasma and lymph, it carries cholesterol from the liver to other cells in the body

A

Low-density lipoprotein (LDL)

153
Q

The hollow cavity inside a tubular structure such as the gut

A

Lumen

154
Q

A slightly milky fluid found in lymph vessels and made up of tissue fluid, fats and lymphocytes

A

Lymph

155
Q

Types of white blood cell responsible for the immune response, they become activated in the presence of antigens

A

Lymphocytes

156
Q

The type of nuclear division in which the number of chromosomes is halved

A

Meiosis

157
Q

Tissue found between the two layers of epidermis in a plant leave comprising an upper layer of palisade cells and a lower layer of spongey cells

A

Mesophyll

158
Q

All the chemical processes that take place in living organisms

A

Metabolism

159
Q

Tiny finger-like projections from the cell-surface membrane of some animals

A

Microvilli

160
Q

Layer made up of pectins and other substances found between the walls of adjacent plant cells

A

Middle lamella

161
Q

The temporary movement of a population of organisms from one locality to another

A

Migration

162
Q

The type of nuclear division in which the daughter cells have the same number of chromosomes as the parent cell

A

Mitosis

163
Q

Term used to describe a large area of land in which only one type of crop is grown

A

Monoculture

164
Q

One of many small molecules that combine to form a larger one known as a polymer

A

Monomer

165
Q

Fatty acid that possesses a carbon chain with a single double bond

A

Mono-unsaturated fatty acid

166
Q

Neurone that transmits action potentials from the central nervous system to an effector

A

Motor neurone

167
Q

Term used to describe a gene that has more than two possible alleles

A

Multiple alleles

168
Q

Any agent that induces a mutation

A

Mutagen

169
Q

A sudden change in the amount or the arrangement of the genetic material in the cell

A

Mutation

170
Q

A fatty substance that surrounds axons and dendrites in certain neurones

A

Myelin

171
Q

Otherwise known as a heart attack, results from the interruption of the blood supply to the heart muscle causing damage to an area of the heart with consequent disruption to its function

A

Myocardial infarction

172
Q

The think filamentous protein found in skeletal muscle

A

Myosin

173
Q

A molecule that carriers electrons and hydrogen ions during aerobic respiration

A

NAD (nicotinamide adenine dinucleotide)

174
Q

A molecule that carries electrons produced in the light-dependent reaction of photosynthesis

A

NADP (nicotinamide adenine dinucleotide phosphate

175
Q

A series of changes, important in homeostasis, that results in a substance being restored to its normal level

A

Negative feedback

176
Q

A nerve cell, comprising a cell body, axon, and dendrites which is adapted to conduct action potentials

A

Neurone

177
Q

A synapse that occurs between a neurone and a muscle

A

Neuromuscular junction

178
Q

One of a number of chemicals that are involved in communication between adjacent neurones or between nerve cells and muscles

A

Neurotransmitter

179
Q

Microorganisms that convert ammonium compounds to nitrites and nitrates

A

Nitrifying bacteria

180
Q

Incorporation of atmospheric nitrogen gas into organic nitrogen-containing compounds

A

Nitrogen fixation

181
Q

A gap in the myelin sheath that surrounds the axon of a neurone

A

Node of Ranvier

182
Q

A bell-shaped curve produced when a certain distribution is plotted on a graph

A

Normal distribution

183
Q

Complex chemicals made up of an organic base, a sugar and a phosphate. They are the basic units of which the nucleic acids DNA and RNA are made

A

Nucleotides

184
Q

The period in the oestrous cycle immediately after ovulation when the female is most fertile

A

Oestrus

185
Q

Mutated versions of proto-oncogenes that result in increased cell division leading to the growth of a tumour

A

Oncogene

186
Q

Means of treating dehydration involving giving, by mouth, a balanced solution of salts and glucose that stimulates the gut to reabsorb water

A

Oral rehydration solution (ORS)

187
Q

The passage of water from a region of high water potential to a region where its water potential is lower, through a partially permeable membrane

A

Osmosis

188
Q

Degeneration of the cartilage of the joints, causing pain and stiffness in these joints

A

Osteoarthritis

189
Q

Chemical reaction involving the loss of electrons

A

Oxidation

190
Q

A chemical reaction I which electrons are transferred from one substance to another substance. Losing electrons is oxidised, gaining electrons is reduced

A

Oxidation-reduction

191
Q

The formation of ATP in the electron transport system of aerobic respiration

A

Oxidative phosphorylation

192
Q

Long, narrow cells packed with chloroplasts that are found in the upper region of a leaf and which carry out photosynthesis

A

Palisade cells

193
Q

An organism that lives on or in a host organism. It gains a nutritional advantage and the host is harmed in some way

A

Parasite

194
Q

Resistance to disease that is acquired from the introduction of antibodies from another individual, rather than an individual’s own immune system

A

Passive immunity

195
Q

Any microorganism that causes disease

A

Pathogen

196
Q

A sugar that possesses five carbon atoms

A

Pentose

197
Q

The chemical bond formed between two amino acids during condensation

A

Peptide bond

198
Q

Mechanism by which cells engulf particles to form a vesicle or a vacuole

A

Phagocytosis

199
Q

The characteristics of an organism, often visible, resulting from both its genotype and the effects of the environment

A

Phenotype

200
Q

Plant tissue that transports the products of photosynthesis from leaves to the rest of the plant

A

Phloem

201
Q

Triglycerides in which one of the three fatty acid molecules is replaced by a phosphate molecule

A

Phospholipid

202
Q

Slitting of a water molecule by light such as occurs during the light-dependent reaction of photosynthesis

A

Photolysis

203
Q

Photograph of an image produced by a microscope

A

Photomicrograph

204
Q

A species that can colonise bare rock or ground

A

Pioneer species

205
Q

A small circular piece of DNA found in bacterial cells

A

Plasmid

206
Q

Fine strands of cytoplasm that extend through pores in adjacent plant cell walls and connect with the cytoplasm of one cell with another

A

Plasmodesmata

207
Q

The shrinkage of cytoplasm away from the cell wall that occurs as a plant cell loses water by osmosis

A

Plasmolysis

208
Q

Group of genes that are responsible for controlling a characteristic

A

Polygenes

209
Q

Large molecule made up of repeating smaller molecules

A

Polymer

210
Q

Group of enzymes that catalyse the formation of long-chain molecules from similar basic units

A

Polymerase

211
Q

Process of making many copies of a specific sequence of DNA or part of a gene

A

Polymerase chain reaction (PCR)

212
Q

Fatty acid that possesses carbon chains with many double bonds

A

Polyunsaturated fatty acid

213
Q

A group of individuals of the same species that occupy the same habitat at the same time

A

Population

214
Q

Process which results in a substance that departs from its normal level becoming further from its norm

A

Positive feedback

215
Q

The sequence of amino acids that makes up the polypeptides of a protein

A

Primary structure of a protein

216
Q

The progressive colonisation of bare rock or other barren terrain by living organisms

A

Primary succession

217
Q

An organism that synthesises organic molecules from simple inorganic ones such as carbon dioxide and water

A

Producer

218
Q

A cell that does not have a nucleus or membrane bound organelles

A

Prokaryotic cell

219
Q

Positively charged sub-atomic particle found in the nucleus of an atom

A

Proton

220
Q

The living portion of a plant cell (i.e. the nucleus and cytoplasm along with the organelles it contains)

A

Protoplast

221
Q

A number of polypeptide chains linked together, and sometimes associated with non-protein groups to form a protein

A

Quaternary structure of a protein

222
Q

A cell adapted to detect changes in the environment

A

Receptor

223
Q

The condition in which the effect of an allele is apparent in the phenotype of a diploid organism only in the presence of another identical allele

A

Recessive allele

224
Q

A nucleotide sequences that is recognised by a restriction endonuclease and to which it attaches

A

Recognition site

225
Q

General term that covers the processes by which genes are manipulated, altered or transferred from organism to organism

A

Recombinant DNA technology

226
Q

Chemical processes involving the gain of electrons

A

Reduction

227
Q

The nerve pathway in the body taken by an action potential that leads to a rapid, involuntary response to a stimulus

A

Reflex arc

228
Q

Period during which the membrane of the axon of a neurone cannot be depolarised and no new action potential can be initiated

A

Refractory period

229
Q

Return to the resting potential in the axon of a neurone after an action potential

A

Repolarisation

230
Q

The difference in electrical charge maintained across the membrane of the axon of a neurone when not stimulated

A

Resting potential

231
Q

A group of enzymes that cut DNA molecules at a specific sequence of bases called a recognition sequence

A

Restriction endonuclease

232
Q

Enzyme that joins together nucleotides to form messenger RNA during transcription

A

RNA polymerase

233
Q

Propagation of a nerve impulse along a myelinated Dendron or axon in which the action potential jumps from one node of Ranvier to another

A

Saltatory conduction

234
Q

A fatty acid in which there are no double bonds between the carbon atoms

A

Saturated fatty acid

235
Q

Also known as a saprophyte, this is an organism that obtains its food from the dead or decaying remains of other organisms

A

Saprobiotic microorganism

236
Q

A section of myofibril between two Z-lines that forms the basic structural unit of the skeletal muscle

A

Sarcomere

237
Q

Cell around a neurone whose cell-surface membrane wraps around the Dendron or axon to form the myelin sheath

A

Schwann cell

238
Q

The way in which the chain of amino acids of the polypeptides of a protein is folded

A

Secondary structure of a protein

239
Q

The recolonization of an area after an early community has been removed or destroyed

A

Secondary succession

240
Q

Process that results in the best-adapted individuals in a population surviving to breed and so pass their favourable alleles to the next generation

A

Selection

241
Q

The environmental force altering the frequency of alleles in a population

A

Selection pressure

242
Q

Breeding of organisms by human selection of parents/gametes in order to perpetuate certain characteristics and/or eliminate others

A

Selective breeding

243
Q

The means by which DNA makes exact copies of itself by unwinding the double helix so that each chain acts as a template for the next

A

Semi-conservative replication

244
Q

A neurone that transmits an action potential from a sensory receptor to the central nervous system

A

Sensory neurone

245
Q

Clear liquid that is left after blood has clotted and the clot has been removed (blood plasma without clotting factors)

A

Serum

246
Q

Inherited blood disorder in which abnormal haemoglobin leads to red cells becoming dickle-shaped and less able to carry oxygen

A

Sickle-cell anaemia

247
Q

An area of heart muscle in the right atrium that controls and coordinates the contraction of the heart (pacemaker)

A

Sinoatrial node (SAN)

248
Q

The muscle that makes up the bulk of the body and which works under conscious control

A

Skeletal muscle

249
Q

Found in the alimentary canal and the walls of blood vessels, its contraction is not under conscious control (unstriated muscle)

A

Smooth muscle

250
Q

Protein channels across cell-surface membranes that use ATP to move sodium ons out of the cell in exchange for potassium ions that move in

A

Sodium-potassium pump

251
Q

The evolution of two or more species from existing species

A

Speciation

252
Q

A group of similar organisms that can breed together to produce fertile offspring

A

Species

253
Q

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

A

Species diversity

254
Q

Selection that tends to eliminate the extremes of the phenotype range within a population. It arises when environmental conditions are constant

A

Stabilising selection

255
Q

Undifferentiated dividing cells that occur in embryos and in adult animal tissues that require constant replacement

A

Stem cell

256
Q

A detectable in the internal or external environment of an organism that produces some change in that organism

A

Stimulus

257
Q

Pore, mostly in the lower epidermis of a leaf through which gases diffuse in and out of the leaf

A

Stoma (plural stomata)

258
Q

The volume of blood pumped at each ventricular contraction of the heart

A

Stroke volume

259
Q

Matrix of a chloroplast where the light-independent reaction of photosynthesis takes place

A

Stroma

260
Q

A substance that is acted on or used by another substance or process

A

Substrate

261
Q

The formation of ATP by the direct transfer of a phosphate group from a reactive intermediate to ADP

A

Substrate-level phosphorylation

262
Q

The liquid portion of a mixture left at the top of the tube when suspended particles have been separated out at the bottom during centrifugation

A

Supernatant liquid

263
Q

Route through the cytoplasm and plasmodesmata of plant cells by which water and dissolved substances are transported

A

Symplastic pathway

264
Q

A junction between neurones in which they do not touch but have a narrow gap, the synaptic cleft, across which a neurotransmitter can pass

A

Synapse

265
Q

The stage in the cardiac cycle in which the heart muscle contracts

A

Systole

266
Q

Tough, flexible but inelastic connective tissue that joins muscles to bone

A

Tendon

267
Q

The folding of a whole polypeptide chain in a precise way, as determined by the amino acids of which it is composed

A

Tertiary structure of a protein

268
Q

The minimum intensity that a stimulus must reach in order to trigger an action potential in a neurone

A

Threshold level/value

269
Q

Formation of a blood clot within a blood vessel that may lead to a blockage

A

Thrombosis

270
Q

Series of flattened membranous sacs in a chloroplast that contain chlorophyll and the associated molecules needed for the light-dependent reaction of photosynthesis

A

Thylakoid

271
Q

The volume of air breathed in and out during a single breath when at rest

A

Tidal volume

272
Q

A group of similar cells organised into a structural unit that serves a particular function

A

Tissue

273
Q

Fluid that surrounds the cells of the body. Its supplies nutrients to the cells and removes waste products

A

Tissue fluid

274
Q

A type of white blood cell that is produced in the bone marrow but matures in the thymus gland. Coordinates the immune response and kills infected cells

A

T cell (T lympphocyte)

275
Q

Formation of messenger RNA molecules from the DNA that makes up a particular gene

A

Transcription

276
Q

Cells that convert a non-electrical signal such as sight or sound into an electrical (nervous) signal and vice versa

A

Transducer cells

277
Q

The process by which one form of energy is converted into another

A

Transduction

278
Q

The transfer of a pathogen from one individual to another

A

Transmission

279
Q

Evaporation of water from a plant

A

Transpiration

280
Q

An individual lipid molecule made up of a glycerol molecule and three fatty acids

A

Triglyceride

281
Q

The position of an organism in a food chain

A

Trophic level

282
Q

A swelling in an organism that is made up of cells that continue to divide in an abnormal way

A

Tumour

283
Q

A gene that maintains normal rates of cell division and so prevents the development of tumours

A

Tumour suppressor gene

284
Q

A plant cell that is full of water, additional entry of water is prevented by the cell wall stopping further expansion of the cell

A

Turgid

285
Q

Filtration assisted by blood pressure

A

Ultrafiltration

286
Q

A fatty acid in which there are one or more double bonds between the carbon atoms

A

Unsaturated fatty acid

287
Q

The introduction of a vaccine containing appropriate disease antigens into the body by injection or mouth in order to induce artificial immunity

A

Vaccination

288
Q

Narrowing of the internal diameter of blood vessels

A

Vasoconstriction

289
Q

Widening of the internal diameter of blood vessels

A

Vasodilation

290
Q

A carrier

A

Vector

291
Q

Protein channel across a cell-surface membrane that opens and closes according to changes in the electrical potential across the membrane

A

Voltage-gated channels

292
Q

The pressure created by water molecules. The measure of the extent to which a solution gives out water

A

Water potential

293
Q

A plant adapted to living in dry conditions

A

Xerophyte

294
Q

Dead, hollow, elongated tubes with lignified side walls and no end walls, that transport water in most plants

A

Xylem vessels