Biology all definitions. Flashcards
1
Q
Antibiotic condition.
A
A non-living feature of an ecosystem.
2
Q
Abundance.
A
The number of individuals of one species in a particular area.
3
Q
Acetylation.
A
Attachment of an acetylene group to something (usually histones).
4
Q
Acetylcholine (ACh).
A
A type of neurotransmitter that binds to cholinergic receptors.
5
Q
Acetyl CoEnzyme A.
A
A type of co-enzyme involved in respiration. It transfers acetate from one molecule to another.
6
Q
Actin.
A
The thin myofilament protein in muscle fibres.
7
Q
Actin - myosin cross bridge.
A
The bond formed when a myosin head binds to an actin filament.
8
Q
Activation energy.
A
Energy that needs to be supplied to start up a reaction.
9
Q
Activator.
A
A transcription factor that increases the rate of transcription.
10
Q
Active site.
A
The part of an enzyme where a substrate molecule binds.
11
Q
Active transport.
A
Movement of molecules and ions across plasma membranes, usually against a concentration gradient, requiring ATP.
12
Q
Adaptation.
A
A characteristic that increases an organisms chances of survival.
13
Q
Adenosine diphosphate (ADP).
A
A molecule made up of adenine, a ribose sugar and two phosphate groups. ATP is synthesises from ADP and a phosphate group.
14
Q
Adrenaline.
A
A hormone secreted from adrenal gland that has many affects, including increasing the blood glucose concentration.
15
Q
Affinity for oxygen.
A
The tendency a molecule has to bind with oxygen.
16
Q
Agglutination.
A
The clumping together of cells for example pathogens and red blood cells.
17
Q
Acquired immunodeficiency syndrome (AIDS).
A
A condition caused by HIV in which the immune system deteriorates and eventually fails.
18
Q
Allele.
A
An alternative version of the same gene.
19
Q
Allele frequency.
A
How often an allele occurs in a population.
20
Q
Allopatric speciation.
A
Where speciation occurs as a result of geographic isolation.
21
Q
Alveolus.
A
A microscopic air sac in the lungs where gas exchange occurs.
22
Q
Amino acids.
A
A monomer of proteins.
23
Q
Ammonification.
A
The process in which nitrogen compounds from dead organisms or waste material are turned into ammonium compounds by sacrobionts.
24
Q
Antibiotic.
A
Medicine designed to kill or inhibit the growth of bacteria.
25
Antibiotic resistance.
When bacteria are able to survive in the presence of antibiotics.
26
Antibody.
A protein produced by B-cells in response to the presence of a pathogen.
27
Antidiuretic hormone (ADH).
A hormone that regulates the water potential of the blood by controlling the permeability of the cells of the distal convoluted tubule and collecting duct in the kidney.
28
Antigen.
A protein that can trigger an immune response.
29
Antigenic variation.
Where pathogens change their antigens.
30
Antigen- presenting cell.
An immune system cell that processes and presents antigens on its surface to activate other immune system cells.
31
Antimicrobial substances.
A substance designed to kill microorganisms.
32
Arteriole.
A blood vessel that branches off an artery.
33
Aseptic technique.
A technique used to prevent the unwanted growth or transfer of microorganisms.
34
Atheroma.
A fibrous plaque cause by the buildup and hardening of white blood cells, lipids and collective tissue.
35
Adenine triphosphate (ATP) .
A molecule made up of adenine, a ribose sugar and three phosphate groups. It is the immediate source of energy in a cell.
36
ATP hydrolase.
An enzyme which catalyses the hydrolysis of ATP into ADP and inorganic phosphate (Pi).
37
ATP - phosphocreatine system.
A system that generates ATP very quickly by phosphorylating ADP using a phosphate group from phosphocreatine.
38
ATP synthase.
An enzyme which catalyses the synthesis of ATP from ADP and Pi.
39
Atrioventricular node (AVN).
A group pf cells in the heart wall that is responsible for passing waves of electrical activity from the SAN onto the bundle of His.
40
Atrioventricular valve (AV)
A valve in the heart linking the ratio to the ventricles.
41
Attachment protein.
A protein on the surface of a virs that lets the virus cling onto a suitable host cell.
42
Autonomic nervous system.
A division of the peripheral nervous system that controls unconscious activities.
43
Autoradiography.
A techniques that reveals the location of radioactive tracers.
44
Autosomal linkage.
When two genes are located on the same autosome and are inherited by the offspring together.
45
Autosome.
A chromosome that isn't a sex chromosome.
46
Base.
A nitrogen - containing molecule that forms part of a DNA nucleotide.
47
B - cell.
A type of white blood cell involved in the immune response which produces antibodies.
48
Benedicts test.
A biochemical test for the presence of sugars.
49
Benign tumour.
Non-cancerous tumour.
50
Bile salt.
A type of salt produced by the liver to aid the digestion of lipids.
51
Binary fission.
The process by which prokaryotic cells replicate.
52
Binomial system.
The system used in classification for naming organisms using two-part latin names.
53
Biodiversity.
The variety of living organisms in an area.
54
Biomass.
The mass of living material in an organism.
55
Biotic condition.
A living feature of an ecosystem.
56
Biuret test.
A biochemical test for the presence of polypeptides and proteins.
57
Bohr effect.
An effect by which an increase of carbon dioxide in the blood results in a reduction of haemoglobin's affinity for oxygen.
58
Bundle of His.
A group of muscle fibres in the heart, responsible for conducting waves of electrical activity from the AVN to the Purkyne tissue.
59
Cancer.
A tumour that invades surrounding tissue.
60
Capillary bed.
A network of capillaries.
61
Capsid.
The protein coat surrounding a virus's genetic material.
62
Capsule.
A layer of secreted slime surrounding some prokaryotic cells.
63
Cardiac cycle.
An ongoing sequence of contraction and relaxation of the atria and ventricles that keeps blood continuously circulating the body.
64
Cardiac output.
The volume of blood pumped by the heart per minute.
65
Cardiomyocyte.
A heart muscle cell.
66
Cardiovascular disease.
Any disease associated with the heart and blood vessels.
67
Carrier.
A person carrying an allele that is not expressed in their phenotype, but that can be passed on to their offspring.
68
Carrier protein.
A protein in a cell membrane that allows the facilitated diffusion of large molecules.
69
Carrying capacity.
The maximum stable popoluation size of a species that an ecosystem can support.
70
Catalyst.
A chemical that speeds up a chemical reaction without being used up.
71
Complementary DNA (cDNA).
A DNA copy of mRNA made using reverse transcriptase.
72
Cell cycle.
The process that all body cells from multicellular organisms use to grow and divide.
73
Cell fractionation.
A method that separates the organelles in a cell.
74
Cell surface membrane.
The membrane found on the surface of animal cells which regulates the movement of substances in and out of the cell.
75
Cellular immune response.
The immune response that involves T-cells and the other immune system cells they interact with.
76
Cellulose.
A polysaccharide made of long, unbranched chains of B-glucose.
77
Cell wall.
The outermost cell layer found in plant, algal and fungal cells.
78
Centromere.
The point at which two strands of a chromosome are joined together.
79
Channel protein.
A protein that forms a pore in a cell membrane and allows the facilitated diffusion of charged particles.
80
Chemical mediator.
A chemical messenger that acts locally.
81
Chemiosmosis.
The process of electrons flowing down the electron transport chain and creating a proton gradient across a membrane to drive ATP synthesis.
82
Chlorophyll.
A photosynthetic pigment found in chloroplasts.
83
Chloroplast.
An organelle present in plant and algal cells where photosynthesis occurs.
84
Cholesterol.
A type of lipid present in cell membranes.
85
Cholinergic synapse.
A synapse that uses the neurotransmitter acetylcholine.
86
Chromatid.
One 'arm' of the double stranded chromosome.
87
Chromosome.
A thread like structure made up of one long DNA molecule.
88
Chromosome non-disjunction.
Failure of the chromosomes to separate properly during meiosis and mitosis.
89
Classification.
The act of arranging organisms into groups.
90
Climax community.
The largest and most complex community of plants and animals an ecosystem can support.
91
Codominant allele.
An allele whose characteristic appears together with another allele in the phenotype because neither allele is recessive.
92
Codon.
A base triplet in DNA or mRNA that codes for an amino acid.
93
Coenzyme.
A molecule that aids the function of an enzyme. They work by transferring a chemical group from one molecule to another.
94
Community.
All the populations of different species in a habitat.
95
Compensation point.
The point at which the rate of photosynthesis in a plant exactly matches its rate of respiration.
96
Competitive inhibitor.
A molecule that has a similar shape to a substrate and blocks an enzymes active site.
97
Complementary base pairing.
Hydrogen bonding between specific pairs of bases on opposing polynucleotide strands.
98
Condensation reaction.
A reaction that releases a molecule of water when it links molecules together.
99
Conservation.
The protection and management of species and habitats in a sustainable way.
100
Co-ordinator.
Part of the nervous system which formulate an appropriate response to a stimulus before sending impulses to an effector.
101
Coronary artery.
An artery supplying the heart muscle with blood.
102
Coronary heart disease.
When the coronary arteries have lots of atheroma in them, which restricts blood flow to the heart.
103
Co-transporter.
A type of carrier protein that binds two molecules at the same time.
104
Courtship behaviour.
Behaviour carried out by organisms to attract a mate of the right species.
105
Crossing over.
When chromatids twist around each other and bits of them swap over during meiosis.
106
Cytokinesis.
The division of the cytoplasm during cell division.
107
Cytoplasm.
A gel-like substance where chemical reactions in a cell happen.
108
Cytotoxic T cell.
A T-cell which kills abnormal or foreign cells.
109
Dehydrogenase.
An enzyme that transfers hydrogen and electrons from one molecule to another.
110
Denatured.
The point at which an enzyme no longer functions as a catalyst.
111
Denitrification.
The process in which nitrates in the soil are converted into nitrogen gas by denitrifying bacteria.
112
Deoxyribose.
The pentose sugar in DNA.
113
Depolarisation.
A decrease in the potential difference across a cell's membrane, making it less negative than the resting potential.
114
Diabetes (Type 1)
A condition in which blood glucose concentration can't be controlled properly because the body doesn't produce any insulin.
115
Diabetes (Type 2).
A condition in which blood glucose concentration can't be controlled properly because the body doesn't produce enough insulin or the body's cells don't respond properly to insulin.
116
Dicotyledonous plant.
A type of flowering plant.
117
Differential reproductive success.
The fact that in any population, some individuals are more likely to survive and reproduce than others.
118
Diffusion.
Net movement of particles form an area of higher concentration to an area of lower concentration.
119
Digestion.
The process of breaking down food into substances that can be used by the body.
120
Dihybrid inheritance.
The inheritance of two characteristics which are controlled by different genes.
121
Dipeptidase.
An endopeptidase enzyme that hydrolyses peptide bonds within a protein.
122
Dipeptide.
A molecule formed from two amino acids.
123
Diploid.
When a cell contains two copies of each chromosome.
124
Directional selection.
Where individuals with alleles for a single extreme phenotype are more likely to survive, reproduce and pass on their alleles.
125
Disaccharide.
A molecule formed from two monosaccharides.
126
Disruptive selection.
Where individuals with alleles for phenotypes at the extreme ends of a range are more likely to survive, reproduce and pass on their alleles.
127
DNA (deoxybribonucleic acid)
The molecule in cells that stores genetic information.
128
DNA helicase.
An enzyme that breaks the hydrogen bonds between two polynucleotide DNA strands during DNA replication.
129
DNA polymerase.
An enzyme that joins together the nucleotides on a new strand of DNA during DNA replication.
130
DNA probe.
A short, single strand of DNA that has a complementary base sequence to part of a target gene.
131
DNA sequencing.
A technique used to determine the order of bases in a section of DNA.
132
Dominant allele.
An allele whose characteristic is always expressed in the phenotype even when there's only one copy.
133
Double-helix.
The structure of a DNA molecule, two separate strands wound together in a spiral.
134
Ecosystem.
All the organisms living in a community plus all the non living conditions in the area in which they live.
135
Effector.
A cell that brings about a response to a stimulus, to produce an effect.
136
Electrochemical gradient.
A concentration gradient of ions.
137
Electron transport chain.
A chain of proteins down which excited electrons flow.
138
Emulsion test.
A biochemical test for the presence of lipids.
139
Endopeptidase.
An enzyme that hydrolyses peptide bonds within a protein.
140
Endoplasmic reticulum.
A system of membranes enclosing a fluid-filled space. Involved with lipid and protein processing.
141
Endothelium.
The inner lining of a blood vessel.
142
Enzyme.
A biological catalyst or a protein that speeds up the rate of chemical reactions.
143
Enzyme-substrate complex.
The intermediate formed when a substrate molecule binds to the active site.
144
Epigenetic control of gene expression.
The attachment or removal of chemical groups to or from DNA or histone proteins which determines whether a gene is switched on or off.
145
Epistasis.
When an allele of one gene masks the expression of the alleles of another gene (s).
146
Eukaryote.
Organism made up of a cell containing a nucleus.
147
Eutrophication.
The process whereby nutrients build up in water, leading to the growth of large quantities of algae. This results in the death of plants, and the decomposition of dead plant matter causes the oxygen content of the water to fall, killing aquatic organisms.
148
Evolution.
Gradual change in a species over time or the change in allele frequency in a population over time.
149
Exchange organ.
An organ specialised to exchange substances.
150
Exocytosis.
The process by which a cell secretes substances using vesicles.
151
Exon.
A section of DNA within a gene that codes for amino acid.
152
Exopeptidase.
An enzyme that hydrolyses the peptide bonds at the end of proteins to remove single amino acids.
153
Expiration.
Breathing out.
154
Extracellular digestion.
When food is broken down outside a cell. Sacrobionts feed using extracellular digestion.
155
Facilitated diffusion.
The diffusion of particles through carrier proteins or channel proteins in the plasma membrane.
156
FAD.
A type of coenzyme involved in respiration. It transfers hydrogen from one molecule to another.
157
Fast twitch muscle fibre.
A muscle fibre that contracts very quickly but also gets tired quickly.
158
Fertilisation.
When a haploid sperm fuses with a haploid egg to generate a diploid zygote.
159
Flagellum.
A long, hair like structure that rotates to move a cell.
160
Fluid mosaic model.
Model describing the arrangement of molecules in a cell membrane.
161
Foreign antigen.
An antigen not normally found in the body.
162
Founder effect.
The reduction in genetic diversity that occurs when just a few organisms from a population start a new colony.
163
Frameshift mutation.
A mutation that changes the number of bases in the DNA code, causing a shift in the base triplets that follow, so that the triplet code is read in a different way.
164
Functional RNA.
RNA molecules that aren't mRNA.
165
Gamete.
A sex cell.
166
Gas exchange.
The process of taking in gases that are needed for life processes and getting rid of waste gases.
167
Gas exchange surface.
A boundary between the outside environment and the internal environment of an organism, over which gas exchange occurs.
168
Gel electrophoresis.
A technique that allows DNA fragments to be separated on a gel according to size.
169
Gene
A section of DNA that codes for a protein which results in a characteristic.
170
Gene expression.
The transcription of a gene into mRNA and translation of the mRNA into a protein.
171
Gene pool.
The complete range of alleles present in a population.
172
Generator potential.
The change in potential difference across a cell membrane due to the presence of a stimulus.
173
Gene technology.
Techniques that allow the study and alteration of genes and their functions.
174
Gene therapy.
Possible treatment option for genetic disorders and some cancers that involves altering defective genes inside cells.
175
Genetic bottleneck.
An event that causes a big reduction in a population and reduces genetic diversity.
176
Genetic code.
The sequence of base triplets in mRNA which code for specific amino acids.
177
Genetic disorder.
An inherited disorder caused by an abnormal gene or chromosome.
178
Genetic diversity.
The number of different alleles of genes in a species or population.
179
Genetic drift.
The process whereby an allele becomes more common in a population due to chance.
180
Genetic engineering.
Recombinant DNA technology.
181
Genetic fingerprint.
A DNA gel that shows the number of times repetitive, non-coding base sequences are repeated at different loci in an individual.
182
Genetic pedigree diagram.
A diagram that shows how an inherited trait runs in a group of related individuals.
183
Genome.
All the genetic material in an organism.
184
Genotype.
The genetic constitution of an organism.
185
Geographical isolation.
When a physical barrier, divides a population of a species.
186
Germ line therapy.
Gene therapy that involves altering the alleles in sex cells.
187
Gill.
The respiratory organ of a fish.
188
Gill filament.
A thin plate in a fish's gill.
189
Glomerular filtrate.
The fluid present in the nephrons of the kidney, following ultrafiltration of the blood to the Bowman's capsule.
190
Glomerulus.
A bundle of capillaries looped inside the Bowman's capsule of a nephron. Where ultrafiltration takes place.
191
Glucagon.
A hormone secreted by the pancreas that has an important role in raising blood glucose concentration.
192
Gluconeogenesis.
The conversion of glycol or amino acids to glucose, activated by glucagon.
193
Glycogen.
A polysaccharide made from a long, very branched chain of a-glucose.
194
Glycogenesis.
The conversion of glucose to glycogen, activated by insulin.
195
Glycogenolysis.
The conversion of glycogen to glucose, activated by glucagon.
196
Glycolipid.
A lipid that has a carbohydrate attached.
197
Glycolysis.
The first stage of aerobic respiration (glucose converted into pyruvate).
198
Glycoprotein.
A protein that has a carbohydrate attached.
199
Glycosidic bond.
A bond formed between monosaccharides.
200
Golgi apparatus.
A group of fluid-filled flattened sacs. Involved with processing and packaging lipids and proteins, and making lysosomes.
201
Golgi vesicle.
A small, fluid filled sac produced by the Golgi apparatus, which stores and transports lipids and proteins.
202
Granum.
A structure in chloroplasts formed from the stacking of thylakoid membranes.
203
Gravitropism.
The growth of a plant in response to gravity.
204
Gross primary production (GPP).
The total amount of chemical energy converted from light energy by plants in a given area.
205
Guard cell.
A cell that controls the opening and closing of stomata.
206
Habitat.
The place where an organism lives within an ecosystem.
207
Haemoglobin.
An oxygen-carrying protein found in red blood cells.
208
Haploid.
When a cell contains one copy of each chromosome.
209
Hardy - Weinberg principle.
A model that predicts that the frequency of alleles in a population won't change from one generation to the next provided that certain conditions are met.
210
What is the equation and what do the letters stand for, in the Hardy-Weinberg principle?
The equation: p^2 + 2pq + q^2 = 1
p^2 = the frequency of the homozygous dominant genotype.
2pq = the frequency of the heterozygous genotype.
q^2 = the frequency of the homozygous recessive genotype.
The equation: p + q = 1
p = the frequency of the dominant allele.
q = the frequency of the recessive allele.
211
Helper T cell.
A T-cell that releases chemical signals to activate other immune system cells.
212
Herd immunity.
Where unvaccinated people are protected because the occurrence of the disease is reduced by the number of people who are vaccinated.
213
Hereditary mutation.
A mutation that's inherited from your parents.
214
Heterozygous.
When an organism carries two different alleles at the same locus.
215
Histone.
A protein that DNA wraps around to form chromatin, which makes up chromosomes.
216
HIV (human immunodeficiency virus).
A virus that affects the human immune system.
217
Homeostasis.
The maintenance of a stable internal environment.
218
Homologous pair.
A pair of matching chromosomes - each chromosomes contains the same genes but could have different alleles.
219
Homozygous.
When an organism carries two copies of the same allele at the same locus.
220
Host cell.
A cell inside which a virus replicates or a cell that is used to carry recombinant DNA.
221
Humoral immune response.
The immune response that involves B-cells, clonal selection and the production of antibodies.
222
Hydrolysis.
A chemical reaction that uses a water molecule when it breaks bonds between molecules.
223
Hydrophyllic.
Attracts water.
224
Hydrophobic.
Repels water.
225
Hydrostatic pressure.
The pressure exerted by a liquid.
226
Hyperpolarisation.
An increase in the potential difference across a cell's membrane, making it more negative than the resting potential.
227
Hypothalamus.
A part of the brain that controls body temperature and monitors the water potential of the blood.
228
Immunity.
The ability to respond quickly to an infection.
229
Immunological comparison.
Using antibodies to determine how similar proteins are.
230
Independent segregation.
The random division of maternal and paternal chromosomes into daughter cells during meiosis.
231
Index of diversity.
A measure of biodiversity that takes into account the number of species present in a community and the abundance of each species.
232
Indoleacetic acid (IAA).
An auxin produced in the tips of shoots and roots in flowering plant.
233
Inorganic ion.
An ion that doesn't contain carbon.
234
Inspiration.
Breathing in.
235
Insulin.
A hormone secreted by the pancreas that has an important role in lowering blood glucose concentration.
236
Interphase.
A period of the cell cycle in which the cell grows and DNA is replicated.
237
Interspecific competition.
Competition between organisms of different species for the same resources.
238
Intraspecific competition.
Competition between organisms for the same species for the same resources.
239
Intron.
A section of DNA within a gene that does not code for amino acids.
240
In vitro cloning.
When a gene copies are made outside of a living organism.
241
In vivo cloning.
When gene copies are made within a living organism.
242
Iodine test.
A biochemical test for the presence of starch.
243
iPS (induced pluripotent stem) cell.
A type of pluripotent stem cell made in the lab reprogramming a specialised adult body cell to express certain transcription.
244
Kinesis.
Non-directional movement in response to a stimulus.
245
Krebs cycle.
The third stage of aerobic respiration. It is a series of oxidation - reduction reactions that produces reduced coenzymes and ATP.
246
Lamella. (chloroplast).
A thin, flat piece of thylakoid membrane found in chloroplasts.
247
Lamella. (fish).
A tiny structure found on the gill filament in a fish.
248
Leaching.
The process in which water-soluble compounds in the soil are washed away.
249
Ligase.
An enzyme that joins together the sticky ends of DNA fragments.
250
Light dependent reaction.
The first step of photosynthesis. Light energy is absorbed by photosynthetic pigments and converted to ATP and reduced NADP.
251
Light independent reaction.
The second step of photosynthesis. ATP and NADP are used to make glucose from carbon dioxide.
252
Link reaction.
The second stage of aerobic respiration where pyruvate is converted into acetyl coenzyme A.
253
Lipase.
An enzyme that catalyses the hydrolysis of lipids.
254
Loading of oxygen.
The action of an oxygen molecule binding with a haemoglobin molecule.
255
Locus.
The position on a chromosome where a particular allele is found.
256
Loop of Henle.
Part of the kidney nephron responsible for establishing the water potential gradient, which allow water to be reabsorbed by the kidney.
257
Lymphatic system.
A network of tubes which transports excess tissue fluid back into the circulatory system.
258
Lysosome.
A round organelle that contains digestive enzymes called lysozymes.
259
Magnification.
How much bigger an image from a microscope is compared to the specimen.
260
Malignant tumour.
A tumour that invades and destroys surrounding tissues.
261
Marker gene.
A gene that can be inserted into transformed cells in order to identify them.
262
Mark-release-recapture.
A method used to estimate the population size of motile organisms.
263
Mass transport system.
A system that carries substances to and from individual cells.
264
Medulla.
A part of the brain that controls heart rate.
265
Meiosis.
A type of cell division where a parent cell divides to create four genetically different haploid cells.
266
Memory cell.
A white blood cell that remains in the body and remembers how to respond to infections.
267
Meristem.
A growing region of a plant.
268
Mesophyll cell.
A type of plant cell present in a leaf and the main gas exchange surface in a plant.
269
Metabolic rate.
The rate at which energy is used by an organism.
270
Methylation.
Attachment of a methyl group to something.
271
Micelle.
A microscopic structure composed of monoglycerides, fatty acids and bile slats.
272
Microarray.
A glass slide with microscopic spots of different DNA probes attached to it in rows.
273
Microfibril.
A strong fibre formed by chains of cellulose linked together by hydrogen bonds.
274
Microvillus.
A fold in the cell surface membrane that increases the surface area.
275
miRNA.
Small, single-stranded RNA molecules that can interfere with the translation of genes.
276
Mitochondrion.
An oval-shaped organelle with a double-membrane. The site of aerobic respiration.
277
Mitosis.
Cel division where a parent cell divides to produce two genetically identical daughter cells.
278
Monoclonal antibody.
An antibody produced from a single group of genetically identical B-cells.
279
Monomer.
Small, basic molecular unit.
280
Monosaccharide.
A monomer of carbohydrates.
281
mRNA.
A type of RNA that is the template for protein synthesis. It carries genetic code from the DNA in the nucleus into the cytoplasm.
282
Multipotent stem cell.
A stem cell only able to develop into a few types of cell.
283
Mutagenic agent.
Something that increases the rate of DNA mutations.
284
Mutation.
A change in the base sequence of an organisms DNA.
285
Mycorrhiza.
A symbiotic relationship between a fungus and the roots of a plant.
286
Myelin sheath.
A layer of Schwann cells around a neurone that acts as an electrical insulator and speeds up conduction of nervous impulses.
287
Myocardial infraction.
A heart attack.
288
Myofibril.
A long, cylindrical organelle within a muscle fibre that's highly specialised for contraction.
289
Myogenic contraction.
When muscle cells are able to contract and relax without receiving signals from nerves.
290
Myosin.
The protein that makes up the thick myofilaments in myofibrils.
291
NAD.
A type of coenzyme involved in respiration. It transfers hydrogen from one molecule to another.
292
NADP
A coenzyme involved in photosynthesis, transferring hydrogen from one molecule to another.
293
Natural selection.
The process whereby an allele becomes common in a population because it codes for a characteristic that makes an organism more likely to survive, reproduce and pass on its genes.
294
Negative feedback mechanism.
A mechanism that restores a level back to normal in a system.
295
Nephron.
One of the filtering units of the kidney, responsible for removing waste products from the blood and involved in controlling the water potential of the blood.
296
Net primary production (NPP).
The energy available to plants for growth and reproduction (after respiratory loss has been deducted from GPP) and the energy available to the next trophic level in a food chain.
297
Net production.
The energy in consumers that is avaliable to the next trophic level in a food chain.
298
Neurotransmitter.
A chemical that transmits a nerve impulse across a synapse.
299
Niche.
The role of a species within its habitat.
300
Nitrification.
The process in which ammonia and ammonium ions in the soil are changed into nitrogen compounds by nitrifying bacteria.
301
Nitrogen fixation.
The process in which nitrogen gas in the atmosphere is turned into nitrogen-contains compounds, such as ammonia.
302
Nodes of ranvier.
A tiny area of bare cell membrane on the surface of a myelinated neurone, where depolarisation can take place.
303
Non-competitive inhibitor.
A molecule that binds away from an enzymes active site and alters the shape of the active site so the substrate can no longer bind.
304
Non-reducing sugar.
A class of monosaccharides and disaccharides.
305
Nucleic acid.
A polymer made from nucleotides.
306
Nucleolus.
A structure within a nucleus that makes ribosomes.
307
Nucleotide.
The monomer that makes up polynucleotides consisting of a pentose sugar, a phosphate group and a nitrogenous organic base.
308
Nucleus.
An organelle that contains chromosomes and controls a eukaryotic cells activities.
309
Oestrogen.
A hormone released by ovaries that stimulates the uterus lining to thicken in the menstrual cycle.
310
Oncogene.
A mutated proton-oncogene that stimulates cells to divide uncontrollably.
311
Organ.
A group of different tissues that work together to perform a particular function.
312
Organ system.
A group of organs that work together to carry out a particular function.
313
Organelle.
A part of a cell.
314
Osmoreceptor.
A cell in the hypothalamus which monitors the water potential of the blood.
315
Osmoregulation.
The regulation of the water potential of the blood.
316
Osmosis.
Diffusion of water molecules across a partially permeable membrane from an area of higher water potential to an area of lower water potential.
317
Oxidation.
A chemical reaction where a molecule loses electrons, and may have lost hydrogen or gained oxygen.
318
Oxidative phosphorylation.
The final stage of aerobic respiration. Energy carried out by electrons, from reduced coenzymes, used to make ATP.
319
Oxygen dissociation curve.
A curve on a graph that shows how saturated with oxygen haemoglobin is at any given partial pressure.
320
Oxyhaemoglobin.
The molecule formed when oxygen binds to haemoglobin.
321
Pacinian corpuscle.
A type of receptor found in your skin which detects mechanical stimuli.
322
Palindromic sequence.
A sequence of DNA bases that consists of antiparallel base pairs.
323
Partially permeable membrane.
A membrane that lets some molecules through it but not others.
324
Pathogen.
An organism that causes disease.
325
PCR (polymerase chain reaction).
A technique used to make millions of identical copies of a DNA fragment in a few hours.
326
Peptidase.
An enzyme that catalyses the hydrolysis of proteins.
327
Peptide bonds.
A bond formed between amino acids.
328
329
Phagocyte.
A type of white blood cell that carries out phagocytosis.
330
Phagocytosis.
The engulfment of pathogens.
331
Phenotype.
The expression of the genetic constitution of an organism and its interaction with the environment.
332
Phenotypic ratio.
The ratio of different phenotypes in the offspring of a genetic cross.
333
Phloem.
A tissue in plants that transports organic substances from their source to their sink.
334
Phospholipid .
A lipid containing one molecule of glycerol attached to two fatty acids and a phosphate group. Main component of the cell membrane.
335
Phosphorylation.
The prices of turning an atom or a molecule into an ion using light energy.
336
Photoionisation.
The process of turning an atom or a molecule into an ion using light energy.
337
Photolysis.
The splitting of a water molecule using light energy into H, e- and O.
338
Photophorylation.
The process of adding phosphate to a molecule using light energy.
339
Photoreceptor.
A receptor in the eye that detects light.
340
Phototropism.
The growth of a plant in response to light.
341
Phylogeny.
the evolutionary history of groups of organisms.
342
Pioneer species.
The first species to colonise an area during succession.
343
Plagioclimax.
The climax community produced when succession is artificially stopped by human activities.
344
Plasma cell.
A type of B-cell that produces antibodies.
345
Plasmid.
A small loop of DNA in a cell, which is not part of the chromosomal DNA.
346
Plasmodesma.
A small channel in a plant cell wall that connects neighbouring plant cell.
347
Pluripotent stem cell.
A stem cell that can develop into any type of cell, apart from cells tat make up the placenta.
348
Polymer.
A large complex molecule composed of long chains of monomers.
349
Polynucleotide.
A molecule made up of lots of nucleotides joined together in a long chain.
350
Polypeptide.
A molecule formed from more than two amino acids.
351
Polysaccharide.
A molecule formed from more than two monosaccharides.
352
Population.
All the organisms of one species in a habitat.
353
Positive feedback mechanism.
A mechanic that amplifies a change away from the normal level in a system.
354
Posterior pituitary gland.
Part of the pituitary gland which secretes hormones such as ADH.
355
Potential difference.
The voltage across a cell membrane.
356
Potometer.
A special piece of apparatus used to estimate transpiration rates.
357
Precise results.
A result close to the mean.
358
Predation.
Where an organism kills and eats another organism.
359
pre-mRNA.
mRNA containing both introns and exons.
360
Primary immune response.
The immune response triggered when a foreign antigen enters the body for the first time.
361
Primary succession.
Succession that happens on newly formed or exposed land with no soil.
362
Primer.
A short piece of single stranded DNA, that is complementary to the new bases at the start of the DNA fragment that wants to be copied.
363
Prokaryote.
Single celled organism without a nucleus or membrane bound organelles.
364
Promoter region.
A DNA sequence that tells the enzyme RNA polymerase where to start producing mRNA.
365
Proteome.
The full range of proteins an organism is able to produce.
366
Proto-oncogene.
A gene that produces proteins that make cells divide.
367
Purkyne tissue.
Fine muscle fibres in the heart that carry waves of electrical activity into muscular walls of the right and left ventricles.
368
Receptor.
A cell, or protein on a cell surface membrane, that detects a stimulus.
369
Recessive allele.
An allele whose characteristic only appears in the phenotype if there are two copies present.
370
Recognition sequence.
A specific palindromic sequence in DNA recognised by a restriction endonuclease.
371
Recombinant DNA.
The name for DNA formed by joining together DNA from different organisms.
372
Recombinant DNA technology.
When DNA from different organisms is joined together by isolating a fragment from a donor organism and inserting it into the DNA of a host organism. Also known as genetic engineering.
373
Reducing sugars.
A class of monosaccharides and disaccharides.
374
Reduction.
A chemical reaction where molecule gains electrons and may have gained a hydrogen or lost in oxygen.
375
Reflex.
A rapid involuntary response to a stimulus.
376
Refractory period.
The period following an action potential in which a neuron cell membrane can't be excited.
377
Repolarisation.
The return of a cell membrane into its resting potential.
378
Repressor.
A transcription factor that inhibits or decreases the rate of transcription.
379
Reproductive isolation.
When changes in audio frequency mean that some individuals of the same species can no longer into breed to produce fertile offspring.
380
Resolution.
How well a microscope distinguishes between two points close together.
381
Respiratory loss.
The amount of energy lost to the environment as heat when organisms respire.
382
Resting potential.
The potential difference across a cell membrane when its cell is at rest.
383
Restriction endonucleases enzyme.
An enzyme that recognises specific recognition sequences and cuts DNA at these places.
384
Restriction map.
A diagram of a piece of DNA showing where different recognition sites of restriction enzymes are found
385
Retina.
The part of the eye containing photoreceptor cells which light is focused onto.
386
Reverse transcriptase.
An enzyme that makes a DNA copy of RNA.
387
Ribosome.
An organelle found in the cell cytoplasm that assembles proteins.
388
Ribulose phosphate carboxylase. (rubisco)
An enzyme which catalyses the formation of glycerate three phosphate from carbon dioxide and RUBP in the independent reaction of photosynthesis.
389
RNA.
A type of nucleic acid similar to DNA but containing ribose instead of deoxyribose sugar and uracil instead of thymine
390
RNA interference.
The mechanism by which siena OR mirna affects translation.
391
RNA polymerase.
An enzyme that synthesises RNA from DNA.
392
Rod (eye).
A photoreceptor cell found in the eye that gives information in black and white.
393
Saltatory conduction.
The process in Myelinated neurons by which a nervous impulse travels between nodes of ranvier.
394
Saprobiont.
A microorganism that feeds on the remains of dead plants and animals using extra cellular digestion to break down the remains.
395
Saprobiotic nutrition.
Obtaining nutrients from dead organic matter using extracellular digestion.
396
Sarcomere.
A short contractile unit that's a part of a myofibril, made up of overlapping myosin and actin filaments.
397
Sarcoplasmic reticulum.
A network of internal membranes that runs through the sarcoplasm. It stores and releases calcium ions that are needed for muscle contraction.
398
Saturated fatty acid.
A fatty acid with no double bonds between its carbon atoms.
399
Schwann cell.
The type of cell that makes up the myelin sheath around neurones.
400
Secondary immune response.
The immune response triggered when a foreign antigen enters the body for the second time.
401
Secondary succession.
Succession that happens on land cleared of all plants but where the soil remains.
402
Second messanger.
A chemical that's produced inside a cell in response to a signal outside the cell. The chemical relays the signal to the inside of the cell.
403
Selective reabsorption.
The reabsorption of useful substances along the kidney nephron back into the blood.
404
Semi-conservative replication of DNA.
Replication of DNA in which half of the new molecules of DNA are from the original piece of DNA.
405
Semi-lunar valve.
A valve in the heart linking the ventricles to the aorta and pulmonary artery.
406
Serial dilution.
The creation of a set of solutions that decrease in concentration by the same factor each time.
407
Sex-linked characteristic.
When the allele that codes for the characteristic is located on a sex chromosome. (x or y).
408
Sink (translocation).
A part of a plant where substances are used up.
409
Sino-atrial node.
A group of cells in the wall of the right atrium that set the rhythm of the heartbeat by sending out regular waves of electrical activity to the atrial walls.
410
siRNA.
A double-stranded RNA molecule that can interfere with the transcription and translation of genes.
411
Sister chromatid.
One of two identical copies of a chromosome joined together in the middle.
412
Sliding filament theory.
The theory that myosin and actin filament slide over one another to make sarcomeres contract.
413
Slow twitch muscle fibre.
A muscle fibre that contracts slowly and can work for a long time without becoming fatigued.
414
Somatic gene therapy.
Gene therapy that involves altering the alleles in body cells.
415
Source (translocation).
A part of a plant where substances needed by a plant are produced.
416
Specialised cell.
A cell adapted to carry out specific functions.
417
Speciation.
The development of a new species from an existing species.
418
Species.
A group of similar organisms that can reproduce to give fertile offspring.
419
Species richness.
The number of different species in a community. A measure of biodiversity.
420
Specific base pairing.
Same def as complementary.
421
Spiracle.
A pore on the surface of an insect.
422
Splicing.
The process by which introns are removed from pre-mRNA strands and exons are joined to from mRNA.
423
Stabilising selection.
Where individuals with alleles for characteristics towards the middle of the range are more likely to survive, reproduce and pass on their alleles.
424
Standard deviation.
A measure of the spread of values about the mean.
425
Starch.
A carbohydrate molecule made up of two polysacchrides - amylase and amylopectin.
426
Stem cell therapy.
Using stem cells to treat or cure medical disorders.
427
Sticky ends.
A small tail of unpaired DNA fragment.
428
Stimulus.
A change in an organisms internal or external environment.
429
Stoma.
A pore in the epidermis of a plant leaf.
430
Stroke volume.
The volume of blood pumped during each heartbeat.
431
Stroma.
A thick fluid found in chloroplasts.
432
Substrate.
A substance that interacts with an enzyme.
433
Succession.
The process by which an ecosystem changes over time.
434
Sugar-phosphate backbone.
Alternating sugar and phosphate groups joined together in a polynucleotide chain.
435
Summation.
The process in which the effect of a neurotransmitter released from many neurones.
436
Supercoiling.
The way that DNA is condensed to fit in the cell in prokaryotes.
437
Surface area: volume ratio.
An organism or structures surface area in relation to its volume.
438
Survival curve.
A graph which shows the percentage of all the individuals that were born in a population that are still alive at any given age.
439
Sympatric speciation.
Where speciation occurs without populations of species being geographically isolated.
440
Synapse.
Junction between a neurone and another neurone, or between a neurone, or between a neurone and an effector cell.
441
Target cell.
A cell that has specific receptors for a particular type of chemical, such as a hormone or neurotransmitter.
442
Taxis (tactic response).
Directional movement in response to a stimulus.
443
Taxon.
A group within a classification hierarchy.
444
T-cell.
A type of white blood cell involved in the immune response. Some types activate B-cells and some kill pathogens directly.
445
Temporary mount.
A method of preparing a microscope slide in which the specimen is suspended in a drop of liquid.
446
Terminator region.
A DNA sequence that tells the enzyme RNA polymerase where to stop producing mRNA.
447
Thylakoid membrane.
A membrane found inside chloroplasts, staked up to form grana.
448
Tissue.
A group of similar cells working together to perform a particular function.
449
Tissue fluid.
The fluid that surrounds cells in tissues.
450
Totipotent stem cell.
A stem cell able to develop into any type of body cell.
451
Toxin.
A harmful molecules released by some pathogens.
452
Trachea (insects).
A pipe that branches off the trachea in an insect and is used for gas exchange.
453
Transcription.
The first stage of protein synthesis, in which a copy of mRNA is made from DNA.
454
Transcription factor.
A protein molecule that controls the transcription of a gene.
455
Transect.
A line used to help find out how non-motile or slow-moving organisms are distributed across an area.
456
Transformed cell.
A host cell that has taken up recombinant DNA.
457
Transformed organism.
An organism hat has had its gene altered by recombinant DNA technology.
458
Translation.
The second stage of protein synthesis, in which amino acids are joined together by ribosomes to make a protein.
459
Translocation.
The movement of solutes to where they're needed in a plant.
460
Transpiration.
The evaporation of water from a plants surface.
461
Triglyceride.
A lipid containing one molecule of glycerol attached to three fatty acids.
462
Triplet.
A series of three bases which codes for one amino acid in a protein.
463
tRNA.
A type of RNA involved in translocation. It carries the amino acids used to make proteins to the ribosomes.
464
Trophic level.
A stage in a food chain.
465
Tropism.
The response of a plant to a directional stimulus.
466
Tropomyosin.
A protein found between actin filaments attached to another protein. Together the two proteins help myofilaments move past each other.
467
Tumour.
A mass of abnormal cells.
468
Tumour suppressor gene.
A gene that slows the rate of cell division by producing proteins that stop cells dividing or cause them to self-destruct.
469
Ultracentrifugation.
A method where cell components are separated out using a centrifuge.
470
Ultrafiltration.
The filtering of the blood that takes place under a high pressure, as blood passes from the glomerulus into the Bowman's capsule.
471
Uncertainty.
The amount of error measurements might have.
472
Unipotent stem cell.
A stem cell that can only differentiate into one type of cell.
473
Unloading of oxygen (from haemoglobin).
The action of an oxygen molecule being released from a haemoglobin molecule.
474
Unsaturated fatty acid.
A fatty acid with at least one double bond between its carbon atoms.
475
Vaccination.
The administering of a vaccine containing antigens to give immunity.
476
Vacuole.
An organelle that contains cell sap.
477
Vector (gene tech).
Something used to transfer DNA into a cell.
478
Ventilation.
Breathing in and out.
479
Virus.
An acellular structure that invades and reproduces inside the cells of other organisms.
480
Visual acuity.
The ability to tell apart points that are close together.
481
Water potential.
Measure of the potential energy in water.
482
Xerophyte.
A plant specially adapted for life in a warm, dry or windy habitat.
483
Xylem.
A tissue in plants that transports water and mineral ions up a plant from the roots to the leaves.
484
Zygote.
The diploid cell formed when two gametes fuse during fertilisation.
