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OCR Biology A-level Definitions > Definitions (all of them - brace yourself) > Flashcards

Definitions (all of them - brace yourself) Flashcards

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1
Q

electron micrograph

A

photograph of an image seen using an electron microscope

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2
Q

magnification

A

the number of times larger an image appears, compared with the size of the object

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3
Q

organelles

A

small structures within cells, each of which has a specific function

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4
Q

photomicrograph

A

photograph of an image seen using an optical microscope

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5
Q

resolution

A

the clarity of an image; the higher the resolution, the clearer the image

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6
Q

eyepiece graticule

A

a measuring device - it is placed in the eyepiece of a microscope and acts as a ruler when you view an object under the microscope

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7
Q

stage graticule

A

a precise measuring device - it is a small scale that is placed on a microscope stage and used to calibrate the value of eyepiece divisions at different magnifications

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8
Q

condensation reaction

A

reaction that occurs when two molecules are joined together with the removal of water

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9
Q

hydrogen bond

A

a weak interaction that can occur whenever molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom

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10
Q

hydrolysis reaction

A

reaction that occurs when a molecule is split into two smaller molecules with the addition of water

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11
Q

monomer

A

a small molecule which binds to many other identical molecules to form a polymer

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12
Q

polymer

A

a large molecule made from many smaller molecules called monomers

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13
Q

carbohydrates

A

a group of molecules containing C, H and O

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14
Q

glycosidic bond

A

a bond formed between two monosaccharides by a hydrolysis reaction

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15
Q

lipids

A

a group of substances that are soluble in alcohol rather than water - they include triglycerides, phospholipids, glycolipids and cholesterol

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16
Q

macromolecule

A

a very large, organic molecule

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17
Q

phospholipid

A

a molecule consisting of glycerol, two fatty acids and one phosphate group

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18
Q

amino acids

A

monomers of all proteins, and all amino acids have the same basic structure

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19
Q

peptide bond

A

a bond formed when two amino acids are joined by a condensation reaction

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20
Q

primary structure

A

the sequence of amino acids found in a molecule

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21
Q

quaternary structure

A

protein structure where a protein consists of more than one polypeptide chain

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22
Q

secondary structure

A

the coiling or folding of an amino acid chain, which arises often as a result of hydrogen bond formation between different parts of the chain - the main forms of secondary structure are the helix and the pleated sheet

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23
Q

tertiary structure

A

the overall three-dimensional shape of a protein molecule. Its shape arises due to interactions including hydrogen bonding, disulfide bridges, ionic bonds and hydrophobic interactions

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24
Q

fibrous protein

A

has a relatively long, thin structure, it is insoluble in water and metabolically inactive, often having a structural role within an organism

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25
Q

globular protein

A

has molecules of a relatively spherical shape, which are soluble in water, and often have metabolic roles within the organism

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26
Q

prosthetic group

A

a non-protein component that forms a permanent part of a functioning protein molecule

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27
Q

double helix

A

shape of DNA molecule, due to coiling of the two sugar-phosphate backbone strands into a right-handed spiral configuration

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28
Q

nucleotide

A

molecule consisting of a five-carbon sugar, a phosphate group and a nitrogenous base

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29
Q

polynucleotide

A

large molecule containing many nucleotides

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30
Q

DNA polymerase

A

enzyme that catalyses formation of DNA from activated deoxyribose nucleotides, using single-stranded DNA as a template

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31
Q

helicase

A

enzyme that catalyses the breaking of hydrogen bonds between the nitrogenous pairs of bases in a DNA molecule

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32
Q

semi-conservative replication

A

how DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand - one old strand is conserved in each new molecule

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33
Q

gene

A

a length of DNA that codes for a polypeptide or for a length of RNA that is involved in regulating gene expression

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34
Q

polypeptide

A

a polymer made of many amino acid units joined together by peptide bonds

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35
Q

transcription

A

the process of making messenger RNA from a DNA template

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36
Q

translation

A

formation of a protein, at ribosomes, by assembling amino acids into a particular sequence according to the coded instructions carried from DNA to the ribosome by mRNA

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37
Q

active site

A

indented area on the surface of an enzyme molecule, with a shape that is complementary to the shape of the substrate molecule

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38
Q

substrate

A

molecule that is altered by an enzyme catalysed reaction

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39
Q

cofactor

A

a substance that has to be present to ensure that an enzyme catalysed reaction takes place at the appropriate rate - some cofactors (prosthetic groups) are part of the enzyme structure, and others (mineral ion cofactors and organic coenzymes) form temporary associations with the enzyme

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40
Q

enzyme-product complex

A

enzyme molecule with product molecule(s) in its active site - the two are joined temporarily by non-covalent forces

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41
Q

enzyme-substrate complex

A

enzyme molecule with substrate molecule(s) in its active site - the two are joined temporarily by non-covalent forces

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42
Q

competitive inhibition

A

inhibition of an enzyme, where the inhibitor molecule has a similar shape to that of the substrate molecule and competes with the substrate for the enzyme’s active site - it blocks the active site and prevents formation of enzyme-substrate complexes

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43
Q

inhibitor

A

a substance that reduces or stops a reaction

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44
Q

non-competitive inhibition

A

inhibition of an enzyme, where the competitor molecule attaches to a part of the enzyme molecule but not the active site - this changes the shape of the active site, which prevents ES complexes forming, as the enzyme active site is no longer complementary in shape to the substrate molecule

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45
Q

glycolipid

A

(phospho)lipid with a chain of carbohydrate molecules attached

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46
Q

glycoprotein

A

protein with a chain of carbohydrate molecules attached

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47
Q

diffusion

A

movement of molecules from an area of high concentration of that molecule to an area of low concentration; it may or may not be across a membrane; it does not involve metabolic energy (ATP)

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48
Q

facilitated diffusion

A

movement of molecules from an area of high concentration of that molecule to an area of low concentration, across a partially permeable membrane via protein channels of carriers; it does not involve ATP

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49
Q

osmosis

A

passage of water molecules down their water potential gradient, across a partially permeable membrane

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50
Q

water potential

A

measure of the tendency of water molecules to diffuse from one region to another

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51
Q

active transport

A

the movement of substances against their concentration gradient across a cell membrane, using ATP and protein carriers

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52
Q

endocytosis

A

bulk transport of molecules, too large to pass through a cell membrane even via a channel of carrier proteins, into a cell

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53
Q

exocytosis

A

bulk transport of molecules, too large to pass through a cell membrane even via channel of carrier proteins, out of a cell

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54
Q

chromatids

A

replicates of chromosomes

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55
Q

cytokinesis

A

division of the cytoplasm of a cell following mitosis

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56
Q

mitosis

A

type of cell division that maintains the chromosome number; each new daughter cell contains the same genetic info as the parent cell - they are also genetically identical to each other

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57
Q

haploid

A

having only one set of chromosomes, represented by the symbol n

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58
Q

homologous chromosomes

A

matching chromosomes, containing the same genes at the same places (loci) - they may contain different alleles for some of the genes

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59
Q

meiosis

A

type of nuclear division that results in the formation of cells containing half the number of chromosomes of the parent cell

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60
Q

differentiation

A

process by which stem cells become specialised into different types of cell

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61
Q

epithelial cells

A

cells that constitute lining tissue

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62
Q

erythrocyte

A

red blood cell

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63
Q

neutrophil

A

type of white blood cell that is phagocytic

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64
Q

stem cell

A

unspecialised cell able to express all of its genes and divide by mitosis

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65
Q

guard cells

A

in leaf epidermis, cells that surround stomata

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66
Q

palisade cells

A

closely-packed photosynthetic cells within leaves

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67
Q

root-hair cells

A

epidermal cells of young roots with long hair-like projections

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68
Q

tissue

A

group of cells that work together to perform a specific function/set of functions

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69
Q

meristem

A

area of unspecialised cells within a plant that can divide and differentiate into other cell types

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70
Q

organ

A

collection of tissues working together to perform a function/related functions

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71
Q

phloem

A

tissue that carries products of photosynthesis, in solution, within plants

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72
Q

xylem

A

tissue that carries water and mineral ions from the roots to all parts of the plant

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73
Q

stem cell

A

unspecialised cell able to express all of its genes and divide by mitosis

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74
Q

gamete

A

sex cell, e.g. ovum/spermatozoon (LOL if that’s what you wanna call it…)

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75
Q

mesenchyme

A

connective tissue

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76
Q

mesoderm

A

the middle of the three layers in the early embryo; gives rise to connective tissue, muscles and part of the gonads (ovaries and testes)

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77
Q

ossification

A

process of changing cartilage to bone by depositing calcium phosphate

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78
Q

surface area to volume ratio

A

the SA of an organism divided by its volume, expressed as a ratio

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79
Q

alveoli

A

tiny folds of the lung epithelium to increase the SA

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80
Q

bronchi and bronchioles

A

smaller airways leading into the lungs

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81
Q

diaphragm

A

a layer of muscle beneath the lungs

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82
Q

intercostal muscles

A

muscles between the ribs - contraction of the external intercostal muscles raises the ribcage

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83
Q

trachea

A

the main airway leading from the back of the mouth to the lungs

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84
Q

cartilage

A

a form of connective tissue

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85
Q

ciliated epithelium

A

a layer of cells that have many hair-like extensions called cilia

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86
Q

elastic fibres

A

protein fibres that can deform and then recoil to their original size

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87
Q

goblet cells

A

cells that secrete mucus

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88
Q

smooth muscle

A

involuntary muscle that contracts without the need for conscious thought

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89
Q

vital capacity

A

the greatest volume of air that can be expelled from the lungs after taking the deepest possible breath

90
Q

buccal cavity

A

the mouth

91
Q

filaments

A

slender branches of tissue that make up the gill - they are often called primary lamellae

92
Q

lamellae (sometimes known as secondary lamellae)

A

folds of the filament to increase SA - they are also called gill plates

93
Q

operculum

A

a bony flap that covers and protects the gills

94
Q

spiracle

A

an external opening or pore that allows air in or out of the tracheae

95
Q

tracheal fluid

A

the fluid found at the ends of the tracheoles in the tracheal system

96
Q

tracheal system

A

a system of air-filled tubes in insects

97
Q

double circulatory system

A

one in which the blood flows through the heart twice for each circuit of the body

98
Q

single circulatory system

A

one in which the blood flows through the heart once for each circuit of the body

99
Q

arteries

A

vessels that carry blood away from the heart

100
Q

arterioles

A

small blood vessels that distribute blood from an artery to the capillaries

101
Q

capillaries

A

very small vessels with very thin walls

102
Q

veins

A

vessels that carry blood back to the heart

103
Q

venules

A

small blood vessels that collect blood from capillaries and lead into the veins

104
Q

hydrostatic pressure

A

the pressure that a fluid exerts when pushing against the sides of a vessel or container

105
Q

lymph

A

the fluid held in the lymphomatic system, which is a system of tubes that returns excess tissue fluid to the blood system

106
Q

oncotic pressure

A

the pressure created by the osmotic effects of the solutes

107
Q

plasma

A

the fluid portion of the blood

108
Q

tissue fluid

A

the fluid surrounding the cells and tissues

109
Q

atrio-ventricular valves

A

valves between the atria and the ventricles, which ensure that blood flows in the correct direction

110
Q

cardiac muscle

A

specialised muscle found in the walls of the heart chambers

111
Q

semilunar valves

A

valves that prevent blood re-entering the heart from the arteries

112
Q

bradycardia

A

a slow heart rhythm

113
Q

ectopic heartbeat

A

an extra beat or an early beat of the ventricles

114
Q

electrocardiogram

A

a trace that records the electrical activity of the heart

115
Q

fibrillation

A

uncoordinated contraction of the atria and ventricles

116
Q

myogenic muscle

A

muscle that can initiate its own contraction

117
Q

purkyne tissue

A

consists of specially adapted muscle fibres that conduct the wave of excitation from the AVN down the septum to the ventricles

118
Q

sino-atrial node (SAN)

A

the heart’s pacemaker - it is a small patch of tissue that sends out waves of electrical excitation at regular intervals in order to initiate contractions

119
Q

tachycardia

A

a rapid heart rhythm

120
Q

affinity

A

a strong attraction

e.g. i have an affinity for Heppy but she can’t know because that would make our friendship weird because I’m gay and she’s not

121
Q

dissociation

A

releasing oxygen from oxyhaemoglobin

122
Q

fetal haemoglobin

A

the type of Hb usually found only in the fetus

123
Q

carbonic anyhydrase

A

the enzyme that catalyses the combination of carbon dioxide and water

124
Q

chloride shift

A

the movement of chloride ions into the erythrocytes to balance the charge as hydrogencarbonate ions leave the cell

125
Q

bohr effect

A

the effect that extra carbon dioxide has on the Hb, explaining the release of more oxygen

126
Q

haemoglobinic acid

A

the compound formed by the buffering action of Hb as it combines with excess hydrogen ions

127
Q

dicotyledonous plants

A

plants with two seed leaves and a branching pattern of veins in the leaf

128
Q

meristem

A

a layer of dividing cells, here it is called the pericycle

129
Q

phloem

A

transports dissolved assimilates

130
Q

vascular tissue

A

consists of cells specialised for transporting fluids by mass flow

131
Q

xylem

A

transports water and minerals

132
Q

companion cells

A

the cells that help to load sucrose into the sieve tubes

133
Q

sieve tube elements

A

make up the tubes in the phloem tissue that carry sap up and down the plant - the sieve tube elements are separated by sieve plates

134
Q

xylem vessels

A

the tubes which carry water up the plant

135
Q

plasmodesmata

A

gaps in the cell wall containing cytoplasm that connects two cells

136
Q

potometer

A

a device that can measure the rate of water uptake, as a leafy stem transpires

137
Q

transpiration

A

the loss of water vapour from the aerial parts of a plant, mostly through the stomata in the leaves

138
Q

adhesion

A

the attraction between water molecules and the walls of the xylem vessel

139
Q

cohesion

A

the attraction between water molecules caused by hydrogen bonds

140
Q

hydrophyte

A

a plant adapted to living in water or where the ground is very wet

141
Q

xerophyte

A

a plant adapted to living in dry conditions

142
Q

assimilates

A

substances that have become part of the plant

143
Q

sink

A

a part of the plant where certain materials are removed from the transport system

144
Q

source

A

a part of the plant that loads materials into the transport system; for example, the leaves photosynthesis and the sugars made are moved to other parts of the plant

145
Q

translocation

A

the transport of assimilates throughout a plant

146
Q

callose

A

a large polysaccharide deposit that blocks old phloem sieve tubes

147
Q

antigen-presenting cell

A

a cell that isolates the antigen from a pathogen and places it on the plasma membrane so that it can be recognised by other cells in the immune system

148
Q

clonal selection

A

selection of a specific B or T cell that is specific to the antigen

149
Q

cytokines

A

hormone-like molecules used in cell signalling to stimulate the immune response

150
Q

neutrophil

A

a type of white blood cell that engulfs foreign matter and traps it in a large vacuole (phagosome) which fuses with lysosomes to digest the foreign matter

151
Q

opsonins

A

proteins that bind to the antigen on a pathogen and then allow phagocytes to bind

152
Q

antibodies

A

specific proteins released by plasma cells that can attach to pathogenic antigens

153
Q

B memory cells

A

cells that remain in the blood for a long time, providing long-term immunity

154
Q

clonal expansion

A

an increase in the number of cells by mitotic cell division

155
Q

interleukins

A

signalling molecules that are used to communicate between different white blood cells

156
Q

plasma cells

A

derived from B lymphocytes, these are cells that manufacture antibodies

157
Q

T helper cells

A

cells that release signalling molecules to stimulate the immune response

158
Q

T killer cells

A

cells that attack and destroy our own body cells that are infected by a pathogen

159
Q

T memory cells

A

cells that remain in the blood for a long time, providing long-term immunity

160
Q

T regulator cells

A

cells that are involved with inhibiting or ending the immune response

161
Q

agglutinins

A

antibodies that cause pathogens to stick together

162
Q

anti-toxins

A

antibodies that render toxins harmless

163
Q

opsonins

A

antibodies that make it easer for phagocytes to engulf the pathogen

164
Q

active immunity

A

where the immune system is activated and manufactures its own antibodies

165
Q

artificial immunity

A

immunity that is achieved as a result of medical intervention

166
Q

natural immunity

A

immunity achieved through normal life processes

167
Q

passive immunity

A

immunity achieved when antibodies are passed to the individual through breast feeding or injection

168
Q

vaccination

A

a way of stimulating an immune response so that immunity is achieved

169
Q

antibiotic

A

a chemical which prevents the growth of microorganisms

170
Q

personalised medicine

A

the development of designer medicines for individuals

171
Q

synthetic biology

A

the re-engineering of biology - this could be the production of new molecules that mimic natural processes, or the use of natural molecules to produce new biological systems that do not exist in nature

172
Q

biodiversity

A

a measure of variation found in the living world

173
Q

habitat

A

where an organism lives

174
Q

species

A

a group of organisms that can freely interbreed to produce fertile offspring

175
Q

allele

A

a version of a gene

176
Q

locus

A

the position of a gene on a chromosome

177
Q

polymorphic gene locus

A

a locus that has more than two alleles

178
Q

species evenness

A

a measure of how evenly represented the species are

179
Q

species richness

A

a measure of how many different species are present

180
Q

monoculture

A

a crop consisting of one strain of one species

181
Q

keystone species

A

one that has a disproportionate effect upon its environment relative to its abundance

182
Q

soil depletion

A

the loss of soil fertility caused by removal of minerals by continuous cropping

183
Q

conservation in situ

A

carrying out active management to maintain the biodiversity in a natural environment

184
Q

conservation ex situ

A

conservation outside the normal habitat of the species

185
Q

CITES

A

the Convention on International Trade in Endangered Species

186
Q

countryside stewardship scheme

A

a scheme to encourage farmers to manage parts of their land in a way that promotes conservation

187
Q

phylogeny

A

the study of the evolutionary relationships between organisms

188
Q

interspecific variation

A

the differences between species

189
Q

intraspecific variation

A

the variation between members of the same species

190
Q

correlation coefficient

A

a measure of how closely two sets of data are correlated - a value of 1 means perfect correlation

191
Q

standard deviation

A

a measure of the spread around a mean

192
Q

students t-test

A

a test used to compare two means

193
Q

cell signalling

A

the way in which cells communicate with each other

194
Q

effector

A

a cell, tissue or organ that brings about a response

195
Q

homeostasis

A

maintaining a constant internal environment despite changes in external and internal factors

196
Q

negative feedback

A

the mechanism that reverses a change, bringing the system back to the optimum

197
Q

positive feedback

A

the mechanism that increases a change, taking the system further away from the optimum

198
Q

sensory receptors

A

cells/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials

199
Q

ectotherm

A

an organism that relies on external sources of heart to maintain body temperature

200
Q

endotherm

A

an organism that uses heat from metabolic reactions to maintain body temperature

201
Q

excretion

A

the removal of metabolic waste from the body

202
Q

metabolic waste

A

a substance that is produced in excess by the metabolic processes in the cells; it may become toxic

203
Q

ornithine cycle

A

a series of biochemical reactions that convert ammonia to urea

204
Q

nephron

A

the functional unit of the kidney

205
Q

ultrafiltration

A

filtration of the blood at a molecular level under pressure

206
Q

antidiuretic hormone (ADH)

A

a hormone that controls the permeability of the collecting duct walls

207
Q

osmoreceptors

A

a sensory receptor that detects changes in water potential

208
Q

glomerular filtration rate (GFR)

A

the rate at which fluid enters the nephrons

209
Q

monoclonal antibodies

A

antibodies made from one type of cell - they are specific to one complementary molecule

210
Q

renal dialysis

A

a mechanism used to artificially regulate the concentrations of solutes in the blood

211
Q

pacinian corpuscle

A

a pressure sensor found in the skin

212
Q

sensory receptors

A

cell/sensory nerve endings that respond to a stimulus in the internal or external environment of an organism and can create action potentials

213
Q

transducer

A

a cell that converts one form of energy into another - in this case to an electrical impulse

214
Q

motor neurones

A

neurones that carry an action potential from the cns to the effector

215
Q

myelinated neurone

A

has an individual later of myelin around it

216
Q

non-myelinated neurone

A

has no individual layer of myelin

217
Q

relay neurones

A

join sensory neurones to motor neurones

218
Q

sensory neurones

A

neurones that carry an action potential from the sensory receptor to the CNS

219
Q

action potential

A

a brief reversal of the potential across the membrane of a neurone causing a peak of +40mV compared to the resting potential of -60mV

220
Q

positive feedback

A

a mechanism that increases a change taking the system further away from the optimum

221
Q

resting potential

A

the potential difference across the membrane while the neurone is at rest

OCR Biology A-level Definitions (1 decks)

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