definitions Flashcards
(584 cards)
1
Q
What is active immunity?
A
Resistance in an organism that has developed through the production of specific antibodies in response to a pathogen. It provides long-lasting immunity as memory cells are produced.
2
Q
What are agglutinins?
A
Chemicals that cause pathogens to aggregate together, aiding phagocytosis. Antibodies can act as agglutinins.
3
Q
What is an antibiotic?
A
A chemical or compound produced by a living organism that kills or prevents the growth of bacteria.
4
Q
What are antibiotic-resistant bacteria?
A
Bacteria that mutate to become resistant to an antibiotic, survive and reproduce very rapidly, passing on their antibiotic resistance.
5
Q
What are antibodies?
A
Immunoglobulins produced by B-lymphocytes in response to a specific antigen, triggering an immune response.
6
Q
What is an antigen?
A
A chemical present on the surface of a cell that induces an immune response.
7
Q
What is an antigen-presenting cell?
A
A macrophage that displays foreign antigens.
8
Q
What are anti-toxins?
A
Chemicals produced by white blood cells that neutralise toxins released by pathogens.
9
Q
What is artificial active immunity?
A
The production of antibodies by the immune system following the exposure to a weakened, attenuated or dead pathogen, e.g: by vaccination.
10
Q
What is artificial passive immunity?
A
The immunity acquired from the administration of specific antibodies from another organism, e.g: by vaccination.
11
Q
What is athlete’s foot?
A
A form of ringworm in humans that affects the feet, resulting in cracking and scaling of the skin.
12
Q
What is an autoimmune disease?
A
A condition in which the immune system attacks and destroys healthy body tissue, e.g: arthritis, lupus.
13
Q
What are bacteria?
A
Prokaryotic cells that have cell walls but lack organelles. Some bacteria are pathogenic, producing toxins that damage host cells.
14
Q
What is bacterial meningitis?
A
A severe form of meningitis caused by bacterial infection of the meninges. Complications include septicaemia; a symptom is a rash of purple discolouration that does not fade when a glass is pressed against it.
15
Q
What are B effector cells?
A
A type of B lymphocyte that divides to form plasma cells.
16
Q
What is black sigatoka?
A
A fungal disease in tomatoes caused by Mycosphaerella fijiensis, the hyphae of which penetrate and digest host leaf cells, turning them black.
17
Q
What are B lymphocytes?
A
Lymphocytes that mature in the bone marrow. There are three main types; plasma cells, B effector cells and B memory cells.
18
Q
What are B memory cells?
A
B lymphocytes that provide immunological memory.
19
Q
What is callose?
A
A plant polysaccharide that contains β-1,3 and β-1,6 linkages between glucose molecules. It is deposited between the cell walls and cell membrane in cells adjacent to infected cells, serving as a defence against pathogens.
20
Q
What are chitinases?
A
Enzymes that degrade chitin in fungal cell walls.
21
Q
What is clonal expansion?
A
The mass proliferation of specific antibody-producing cells.
22
Q
What is clonal selection?
A
The identification of an antibody-producing cell with complementary receptors to the shape of a specific antigen.
23
Q
What is Clostridium difficile?
A
A type of bacteria found in the gut of some individuals which is resistant to most antibiotics.
24
Q
What is a communicable disease?
A
A disease that is caused by a pathogen and transmitted directly between organisms.
25
What are cytokines?
Cell-signalling molecules produced by mast cells in damaged tissue. They attract white blood cells to the site of damage.
26
What is direct transmission?
The transfer of a pathogen directly from one organism to another via direct contact, ingestion or the sharing of contaminated needles.
27
What is an epidemic?
A rapid rise in the incidence of a communicable disease at a local or national level.
28
What are expulsive reflexes?
Coughs or sneezes initiated upon irritation of the respiratory tract. They remove microorganism-containing mucus from the gaseous exchange system.
29
What are fungi?
Eukaryotic, often multicellular organisms that may cause disease. They digest and destroy cells, and produce spores that can spread rapidly between organisms.
30
What are glucanases?
Enzymes produced by plants that decompose glucans, polysaccharides found in oomycete cell walls.
31
What is histamine?
A chemical produced by mast cells in damaged tissue. It makes blood vessels dilate and causes their walls to become leakier.
32
What is Human Immunodeficiency Virus (HIV)?
An infectious virus that destroys T helper cells, weakening the immune system of the body. HIV makes an individual more susceptible to opportunistic infections and can lead to AIDS.
33
What is indirect transmission?
The transfer of a pathogen indirectly between organisms via fomites, vectors, droplet infection or soil contamination.
34
What is inflammation?
A localised response of vascular tissue to pathogens, damage or irritants. It is characterised by pain, redness, heat and swelling.
35
What is influenza?
A common viral infection caused by the family of viruses, Orthomyxoviridae, that destroys ciliated epithelial cells in the gaseous exchange system, exposing the airways to secondary infection.
36
What are interleukins?
Cytokines produced by T helper cells that stimulate B cells.
37
What are lymphocytes?
White blood cells that contribute to the specific immune response.
38
What is a lysosome?
A membrane-bound organelle that contains hydrolytic enzymes.
39
What is malaria?
A disease caused by the protoctista Plasmodium that lives within two hosts, mosquitoes and humans. It causes recurrent episodes of fever and can be fatal.
40
What are mast cells?
Specialised cells in connective tissue that are important in the inflammatory response, releasing histamines and cytokines.
41
What is MRSA?
A type of bacteria that is resistant to the antibiotic methicillin.
42
What are mucous membranes?
The membranes lining body cavities that secrete a sticky mucus.
43
What is natural active immunity?
The production of antibodies by the immune system following infection.
44
What is natural passive immunity?
The immunity acquired by an infant mammal when antibodies are transferred through the placenta and the colostrum from the mother.
45
What are non-specific defences?
Defenses that are always present and are the same for all organisms, e.g: skin, blood clotting, inflammation, mucous membranes and expulsive reflexes.
46
What are opsonins?
Chemicals that bind to and tag foreign cells, making them easily recognisable to phagocytes.
47
What is passive immunity?
Resistance in an organism acquired via the transfer of antibodies. It provides short-term immunity as no memory cells are produced.
48
What is a pathogen?
A disease-causing microorganism. Includes bacteria, viruses, fungi and protoctista.
49
What is penicillin?
The first conventional, effective and safe antibiotic derived from the mould Penicillium chrysogenum. It was discovered by Alexander Flemming.
50
What is personalised medicine?
A form of medical care that enables doctors to provide healthcare that is customised to an individual's genotype.
51
What are phagocytes?
Specialised white blood cells that engulf and destroy pathogens. There are two types: neutrophils and macrophages.
52
What is phagocytosis?
The process by which phagocytes engulf and destroy pathogens.
53
What is a phagolysosome?
A vesicle within a phagocyte formed by the fusion of a phagosome and lysosome.
54
What is a phagosome?
The vacuole inside a phagocyte in which a foreign particle is engulfed.
55
What are plasma cells?
B lymphocytes that produce antibodies specific to a particular antigen.
56
What is potato blight?
A disease caused by the fungi-like protoctist Phytophthora infestans whose hyphae penetrate host cells, causing the collapse and decay of the leaves, fruit and tubers.
57
What is the primary immune response?
The response of the immune system to a pathogen when it is first encountered. A small number of antibodies are produced slowly.
58
What is protoctista?
A group of eukaryotic, single-celled microorganisms that may cause disease.
59
What is ring rot?
A bacterial disease in tomatoes, potatoes and aubergines that results in damage to the leaves, fruit and tubers. It is caused by the Clavibacter michiganensis bacterium.
60
What is ringworm?
A fungal disease that affects mammals, causing grey-white, circular, crusty lesions on the skin.
61
What is the secondary immune response?
The response of the immune system to a pathogen when it is encountered for a second (third, fourth…etc.) time. Immunological memory gives a rapid production of a large number of antibodies.
62
What is synthetic biology?
The design and construction of new biological entities, as well as the reconstruction of pre-existing natural biological systems.
63
What are T helper cells?
T lymphocytes with CD4 receptors on the cell surface membrane. These bind to antigens on antigen-presenting cells and secrete interleukins.
64
What are T killer cells?
T lymphocytes that produce perforin, destroying pathogens with a specific antigen.
65
What are T lymphocytes?
Lymphocytes that mature in the thymus gland. There are four main types: T helper cells, T killer cells, T memory cells and T regulatory cells.
66
What are T memory cells?
T lymphocytes that provide immunological memory.
67
What is tobacco mosaic virus (TMV)?
A virus that infects many species of plants, in particular tobacco plants. It damages the leaves, flowers and fruit, and stunts plant growth.
68
What are T regulator cells?
T lymphocytes that regulate the immune response by suppressing other T cells and maintaining tolerance to self-antigens.
69
What is tuberculosis (TB)?
A bacterial disease, caused by Mycobacterium tuberculosis and M. bovis, that damages lung tissue and weakens the immune system.
70
What is vaccination?
The deliberate exposure of an individual to antigens from a pathogen to provide artificial active immunity.
71
What is a vector?
A living or non-living agent that transmits a pathogen between organisms.
72
What are viruses?
Non-living infectious agents that invade host cells and take over cell metabolism, replicating within them.
73
What is adaptation?
A feature of an organism that increases its chance of survival in its environment. An adaptation may be anatomical, physiological or behavioural.
74
What is a belt transect?
A line along a sampled area upon which quadrats are placed at intervals to determine the abundance and distribution of organisms in an ecosystem.
75
What is the binomial system?
The universal system of naming organisms. It is made up of two parts; the first gives the genus and the second, the species e.g. Homo sapiens.
76
What is biodiversity?
The variety of living organisms in an ecosystem.
77
Who is Charles Darwin?
The scientist who developed the theory of evolution by natural selection.
78
What is classification?
The organisation of organisms into groups.
79
What is a community?
All of the populations of different species living together in a habitat.
80
What is conservation?
The maintenance of ecosystems and biodiversity by humans in order to preserve the Earth’s resources.
81
What is continuous variation?
When a characteristic can have any value within a given range e.g. height, mass, heart rate.
82
What is the Convention on Biological Diversity (CBD)?
A treaty that promotes the sustainable use of and maintenance of biodiversity. One of three Rio Conventions.
83
What is the Convention on International Trade in Endangered Species (CITES)?
A treaty that regulates the trade of plants and wild animals across international borders.
84
What is convergent evolution?
The process by which unrelated species evolve similar traits due to exposure to similar environments or selection pressures.
85
What is the Countryside Stewardship Scheme (CSS)?
A scheme in England (1991-2014) that aimed to provide financial incentives to farmers to enhance and conserve the environment.
86
What is discontinuous variation?
When a characteristic can only take certain values e.g. sex, eye colour, blood group.
87
What is a domain?
The highest taxonomic rank. There are three domains; Archaea, Bacteria and Eukaryota.
88
What is evolution?
The gradual change in the allele frequencies within a population over time. Occurs due to natural selection.
89
What is ex situ conservation?
A type of conservation that takes place outside of an organism’s natural habitat e.g. zoos, botanic gardens, seed banks.
90
What is a fossil?
The remains of dead organisms found in rocks which are millions of years old.
91
What is fungi?
A biological kingdom consisting of mushrooms, yeasts and moulds.
92
What is genetic biodiversity?
A measure of the variety of genes that make up a species.
93
What is habitat biodiversity?
A measure of the number of different habitats found within an area.
94
What is in situ conservation?
A type of conservation that takes place within an organism’s natural habitat e.g. wildlife reserves, marine conservation zones.
95
What is interspecific variation?
Differences between members of different species.
96
What is intraspecific variation?
Differences between members of the same species.
97
What is a keystone species?
A species which has an unexpectedly large effect on the environment and is crucial for the maintenance of biodiversity.
98
What is kick-sampling?
A method used to sample organisms living on the bed of a river. It involves disturbing an area of river bed before placing a net downstream to capture released organisms.
99
What is a kingdom?
The second highest taxonomic rank. There are five kingdoms: Prokaryotae, Protoctista, Fungi, Plantae and Animalia.
100
What is a line transect?
A line along a sampled area. The species touching the transect at regular intervals are recorded to determine the abundance and distribution of organisms in an ecosystem.
101
What is monoculture?
The growth of one crop in a given area.
102
What is natural selection?
The process by which the frequency of ‘advantageous’ alleles gradually increases in a population’s gene pool over time.
103
What is non-random sampling?
A sampling method in which a sample is not chosen randomly. Three types; opportunistic, stratified and systematic.
104
What is opportunistic sampling?
A type of non-random sampling that involves drawing a sample from part of the population that is conveniently available.
105
What is a phylogenetic tree?
A diagram used to show the evolutionary relationships between organisms.
106
What is phylogeny?
The evolutionary relationships between individuals or groups of organisms.
107
What is a pitfall trap?
A device used to catch small ground surface invertebrates. It consists of a container buried beneath the ground and a roof structure.
108
What are pooters?
A device used in the collection of small insects. It consists of two tubes, one connecting the holding chamber to a mouthpiece (with a filter) and the other to an inlet tube.
109
What are prokaryotae?
A biological kingdom consisting of unicellular prokaryotes (bacteria).
110
What is the proportion of polymorphic gene loci?
A measure of genetic biodiversity.
111
What is protoctista?
A biological kingdom consisting of unicellular eukaryotes.
112
What is a quadrat?
A square grid of known area used in sampling to determine the abundance of organisms in a habitat. There are two types; point quadrats and frame quadrats.
113
What is random sampling?
A sampling technique used to avoid bias e.g. creating a square grid and generating random coordinates.
114
What is a seed bank?
A storage of seeds to preserve genetic material.
115
What are selection pressures?
Environmental factors that drive evolution by natural selection and limit population sizes e.g. competition, predation and disease.
116
What is Simpson’s Index of Diversity (D)?
A measurement of diversity that considers both species richness and evenness.
117
What is Spearman’s rank correlation coefficient?
A statistical test used to determine the relationship between two variables.
118
What is species biodiversity?
A measure of species richness and species evenness.
119
What is species evenness?
The number of individuals of each species living together in a community.
120
What is species richness?
The number of different species found within an area.
121
What is stratified sampling?
A type of non-random sampling in which populations are divided into subgroups and samples are taken from each.
122
What is stratified sampling?
A type of non-random sampling in which populations are divided into strata and a random sample is taken from each, proportional to its size.
123
What is Student’s t-test?
A statistical test used to analyse whether there is a significant difference between the means of data values of two populations.
124
What are sweep nets?
A funnel-shaped net used to catch insects and other small animals.
125
What is systematic sampling?
A type of non-random sampling in which samples are taken from different regions of a habitat.
126
What is a taxon?
Each group within a phylogenetic classification system.
127
What is taxonomic hierarchy?
The arrangement of organisms into successive levels of classification known as taxonomic groups.
128
What is the three-domain system?
A method of classification in which organisms are categorised into three domains and six kingdoms. Developed by Carl Woese.
129
What is a Tullgren funnel?
A device used to extract living organisms from a soil sample.
130
What is variation?
The differences between individuals due to genes, the environment or a combination of both.
131
132
What is an allele?
A version of a gene.
133
What is allopatric speciation?
A form of speciation that occurs when two populations become geographically isolated due to a physical barrier.
134
What is apoptosis?
Programmed cell death, important for pruning surplus cells and tissues in development.
135
What is artificial selection?
See ‘selective breeding’.
136
What is autosomal linkage?
When two or more genes are positioned on the same autosome and are often inherited together.
137
What is an autosome?
A chromosome that is not an X or Y chromosome.
138
What is bioinformatics?
The development of computer tools and software required to organise and analyse unprocessed biological data.
139
What is the chi-squared (X²) test?
A statistical test used to determine whether a pattern of inheritance is statistically significant.
140
What is chlorosis?
A condition in which plant leaf cells produce insufficient chlorophyll, resulting in pale or yellow leaves.
141
What is codominance?
When both alleles for a gene in a heterozygous organism equally contribute to the phenotype.
142
What is computational biology?
The use of computational techniques to analyse large amounts of biodata and build theoretical models of biological systems.
143
What is continuous variation?
A type of variation that cannot be categorised, producing a continuous range in which a characteristic can take any value.
144
What are degrees of freedom in the chi-squared test?
The number of categories minus one.
145
What is deletion in genetics?
A form of gene mutation in which one or more nucleotide bases are removed from a DNA sequence.
146
What is dihybrid inheritance?
The determination of a trait by the inheritance of two genes.
147
What is directional selection?
A type of selection that favours one extreme phenotype and selects against all other phenotypes.
148
What is discontinuous variation?
A type of variation that can be categorised, where a characteristic can only appear in discrete values.
149
What is disruptive selection?
A type of selection that favours individuals with extreme phenotypes and selects against those with phenotypes close to the mean.
150
What is a DNA barcode?
A short sequence of DNA used to identify a species.
151
What is DNA ligase?
An enzyme that joins the sugar-phosphate backbone of two DNA segments.
152
What is DNA profiling?
A technique used to determine the patterns in the non-coding DNA of an individual.
153
What is DNA sequencing?
Determining the entire DNA nucleotide base sequence of an organism.
154
What is a dominant allele?
An allele that is always expressed, represented by a capital letter.
155
What is electrophoresis?
A type of chromatography that separates nucleic acid fragments or proteins by size using electric current.
156
What is electroporation?
A method of transformation using a small electric current to transfer recombinant plasmids into bacterial cells.
157
What is epistasis?
A relationship between genes at different loci, where the allele of one gene affects the expression of a different gene.
158
What is etiolation?
A condition in plants characterised by weak stems and small, pale leaves due to insufficient exposure to light.
159
What is evolution?
The gradual change in the allele frequencies within a population over time due to natural selection.
160
What is an exon?
A sequence of DNA that codes for an amino acid sequence.
161
What is the founder effect?
A type of genetic drift in which a few individuals of a species break off from the population and form a new colony.
162
What is a gene mutation?
A change to at least one nucleotide base in DNA or the arrangement of bases.
163
What is gene therapy?
A therapeutic technique in which a faulty allele is replaced with a functional allele to treat or prevent disease.
164
What is a genetically modified organism (GMO)?
An organism that has had its genome altered.
165
What is a genetic bottleneck?
A drastic reduction in population size leading to reduced genetic diversity within a population.
166
What is genetic drift?
Random variations in allele frequencies in small populations due to mutations.
167
What is genetic engineering?
The modification of the genome of an organism by inserting a desired gene from another organism.
168
What is a genome?
The complete genetic material of an organism.
169
What is a genotype?
An organism’s genetic composition, describing all alleles.
170
What is germ line cell gene therapy?
A type of gene therapy in which a faulty allele is replaced with a functional allele in germ cells or a very early embryo.
171
What is the Hardy-Weinberg principle?
A model predicting that the ratio of dominant and recessive alleles in a population will remain constant under certain conditions.
172
What is heterozygous?
When someone has two different alleles of a gene.
173
What is high-throughput sequencing?
Large-scale approaches to DNA sequencing that enable many clusters of DNA fragments to be sequenced simultaneously.
174
What are homeobox genes?
A group of regulatory genes responsible for the development of body plans in different organisms.
175
What is homozygous?
When someone has two identical alleles of a gene.
176
What is a Hox gene?
A type of homeobox gene present in animals.
177
What is inbreeding?
The formation of offspring from the breeding of closely related individuals.
178
What is insertion in genetics?
A form of gene mutation in which one or more nucleotide bases are added to a DNA sequence.
179
What is an intron?
A non-coding sequence of DNA.
180
What is the lac operon?
A group of three structural genes required for the metabolism of lactose.
181
What is mature mRNA?
The final mRNA product that has had introns removed and undergone other post-transcriptional changes.
182
What is mitosis?
A form of cell division that produces two genetically identical diploid daughter cells.
183
What is monogenic inheritance?
The determination of a trait by the inheritance of a single gene.
184
What are multiple alleles?
When a gene has more than two potential alleles.
185
What is a mutagen?
An agent that increases the rate of gene mutations above normal levels.
186
What is an operon?
A group of genes that are expressed together and controlled by the same regulatory mechanism.
187
What is a phenotype?
An organism’s observable characteristics due to interactions of the genotype and the environment.
188
What is the Polymerase Chain Reaction (PCR)?
An in vitro technique used to rapidly amplify fragments of DNA.
189
What is post-transcriptional control?
The level of gene regulation in which primary mRNA can be modified, controlling translation.
190
What is post-translational control?
The level of gene regulation in which proteins can be modified post-synthesis.
191
What is pre-mRNA?
The product of transcription before any post-transcriptional regulation.
192
What is a recessive allele?
An allele that is only expressed in the absence of a dominant allele.
193
What is recombinant DNA?
A combination of DNA from two different organisms.
194
What is a regulatory gene?
A gene that codes for the production of proteins involved in DNA regulation.
195
What is a repressor protein?
A protein that binds to the operator, altering the transcription rate.
196
What are restriction endonucleases?
Enzymes that cut DNA molecules at recognition sequences, creating sticky ends.
197
What is Sanger sequencing?
The first method of DNA sequencing that involved the formation of DNA fragments of varying lengths.
198
What are selection pressures?
Factors that affect an organism’s ability to survive in an environment.
199
What is selective breeding?
The process by which humans artificially select organisms with desirable characteristics.
200
What is sex-linkage?
The presence of a gene on an X or Y chromosome.
201
What is sexual reproduction?
A form of reproduction involving the random fusion of male and female gametes.
202
What is somatic cell gene therapy?
A type of gene therapy in which a faulty allele is replaced with a functional allele in affected somatic cells.
203
What is speciation?
The formation of new species due to the evolution of two reproductively separated populations.
204
What is stabilising selection?
A type of selection that favours individuals with phenotypes close to the mean and selects against extreme phenotypes.
205
What are sticky ends?
The staggered cut formed by restriction endonucleases in double-stranded DNA.
206
What is a structural gene?
A gene that codes for the production of proteins or enzymes that are not involved in DNA regulation.
207
What is substitution in genetics?
A form of gene mutation in which one nucleotide base is exchanged for another.
208
What is sympatric speciation?
A form of speciation that occurs when two populations within the same area become reproductively isolated.
209
What is synthetic biology?
The design and construction of new biological entities, as well as the reconstruction of pre-existing natural biological systems.
210
What is a thermocycler?
A machine controlled by a computer that varies temperatures at predetermined time intervals.
211
What is transcriptional control?
The level of gene regulation in which genes are switched ‘on’ or ‘off’.
212
What are transcription factors?
Proteins that help to switch genes ‘on’ or ‘off’ by controlling the binding of RNA polymerase to DNA.
213
What is a transgenic organism?
An organism that contains recombinant DNA.
214
What is translational control?
The level of gene regulation in which translation can be initiated or stopped.
215
What is a vector in genetics?
A carrier used to transfer a gene from one organism to another.
216
What is artificial twinning?
The artificial production of monozygotic twins from the manual splitting of the early embryo.
217
What are aseptic techniques?
A range of techniques used to culture microorganisms under sterile conditions.
218
What is batch fermentation?
An industrial method of fermentation that runs for a set period of time.
219
What is bioremediation?
The use of microorganisms to remove soil and water pollution.
220
What is biotechnology?
The field of biology involving the use of living systems to produce or transform materials.
221
What is brewing?
The production of beer from the steeping of barley in water and fermentation with yeast.
222
What are clones?
Genetically identical offspring produced as a result of cloning.
223
What is cloning?
A method of producing genetically identical offspring by asexual reproduction.
224
What is continuous fermentation?
An industrial method of fermentation in which culture broth is continuously removed.
225
What is culture in biology?
The growth of living matter in vitro in suitable conditions.
226
What is cutting in horticulture?
A small section of the root or stem of an adult plant used to produce natural clones.
227
What is enucleation?
The removal of the nucleus.
228
What is fermentation?
A type of anaerobic respiration that does not involve an electron transport chain.
229
What is immobilised aminoacylase?
An immobilised enzyme used to produce pure samples of L-amino acids.
230
What are immobilised enzymes?
Enzymes attached to an inert, insoluble material over which the substrate passes.
231
What is immobilised glucoamylase?
An immobilised enzyme used to breakdown dextrins into glucose.
232
What is immobilised glucose isomerase?
An immobilised enzyme used to convert glucose to fructose.
233
What is immobilised lactase?
An immobilised enzyme that hydrolyses lactose to glucose and galactose.
234
What is immobilised penicillin acylase?
An immobilised enzyme used to produce semi-synthetic penicillins from natural penicillins.
235
What is micropropagation?
The production of large numbers of clones from one parent plant using tissue culture.
236
What are monozygotic twins?
Identical twins formed from one fertilised egg that splits to form two embryos.
237
What is natural cloning?
A form of asexual reproduction that takes place in plants.
238
What is penicillin?
The first conventional, effective and safe antibiotic derived from the mould Penicillium chrysogenum.
239
What is somatic cell nuclear transfer (SCNT)?
The production of an embryo from the transfer of the nucleus of an adult animal cell to an enucleated egg cell.
240
What is tissue culture?
The growth of cells or tissues outside of an organism in an artificial culture medium.
241
What are abiotic factors?
The non-living aspects of an ecosystem.
242
What is abundance in ecology?
The number of individuals per species in a specific area at any given time.
243
What is ammonification?
The production of ammonium compounds when decomposers feed on organic nitrogen-containing molecules.
244
What is Azotobacter?
A type of nitrogen-fixing bacteria that lives freely in the soil.
245
What is a belt transect?
A line along a sampled area upon which quadrats are placed at intervals.
246
What is biomass?
The total mass of organic material in a specific area over a set time period.
247
What are biotic factors?
The living components of an ecosystem.
248
What is the carbon cycle?
The cycle through which carbon moves between living organisms and the environment.
249
What is carrying capacity?
The maximum population size that can be indefinitely supported by an environment.
250
What is a climax community?
The stable community of organisms that exists at the final stage of ecological succession.
251
What are the living components of an ecosystem?
The living components of an ecosystem include food availability, pathogens, predators, and other species.
252
What is the carbon cycle?
The cycle through which carbon (in the form of carbon dioxide) moves between living organisms and the environment, involving respiration, photosynthesis, and combustion.
253
What is conservation?
The maintenance of ecosystems and biodiversity by humans in order to preserve the Earth’s resources.
254
What are consumers?
Organisms that feed on other organisms to obtain energy.
255
What are decomposers?
Organisms that release enzymes which catalyse the breakdown of dead plant and animal material into simpler organic matter.
256
What is deflected succession?
Changes to the natural flow of succession due to human activity that result in a stable community known as a plagioclimax.
257
What is denitrification?
The conversion of nitrate ions to nitrogen gas by denitrifying bacteria.
258
What are denitrifying bacteria?
Anaerobic microorganisms, found in waterlogged soils, responsible for the reduction of nitrate ions to nitrogen gas.
259
What is distribution in ecology?
The spread of living organisms in an ecosystem.
260
What is ecological efficiency?
The efficiency of energy or biomass transfer between trophic levels.
261
What is an ecosystem?
The community of organisms (biotic) and non-living (abiotic) components of an area and their interactions.
262
What is a food chain?
Describes the feeding relationships between organisms and the resulting stages of biomass transfer. It takes the form: producer ⟶ primary consumer ⟶ secondary consumer ⟶ tertiary consumer.
263
What is interspecific competition?
A type of competition that takes place between members of different species.
264
What is intraspecific competition?
A type of competition that takes place between members of the same species.
265
What is a limiting factor?
A variable that limits the rate of a particular process.
266
What is a line transect?
A line along a sampled area. The species touching the transect at regular intervals are recorded to determine the abundance and distribution of organisms in an ecosystem.
267
What is nitrification?
The conversion of ammonium ions to nitrate ions by nitrifying bacteria, taking place in two stages.
268
What are nitrifying bacteria?
Aerobic microorganisms found in the soil responsible for the oxidation of ammonium ions to nitrate ions.
269
What is Nitrobacter?
A genus of nitrifying bacteria that oxidises nitrites into nitrates.
270
What is the nitrogen cycle?
The cycle through which nitrogen moves between living organisms and the environment, involving ammonification, nitrification, nitrogen fixation, and denitrification.
271
What is nitrogen fixation?
The conversion of atmospheric nitrogen gas into ammonia by nitrogen-fixing bacteria in the soil or root nodules of legumes.
272
What are nitrogen-fixing bacteria?
Microorganisms responsible for the conversion of atmospheric nitrogen gas into nitrogen-containing compounds. They can be free-living or mutualistic.
273
What is Nitrosomonas?
A genus of nitrifying bacteria that oxidises ammonium compounds into nitrites.
274
What are peat bogs?
Areas of peat soil in wetland habitats formed by the accumulation of partially decayed organic matter. They store carbon and are commonly referred to as ‘carbon sinks’.
275
What are pioneer species?
Species that can survive in hostile environments and colonise bare rock or sand, e.g., lichens.
276
What is plagioclimax?
A stage in succession in which artificial factors prevent the formation of a natural climax community.
277
What is a population?
All organisms of the same species living with one another in a habitat at the same time.
278
What is a predator?
An organism that eats other organisms.
279
What is preservation?
The restriction of human interference in an area in order to protect and maintain the ecosystem.
280
What is prey?
An organism that is eaten by predators.
281
What is primary succession?
A type of succession in which pioneer species colonise a newly formed or exposed area of land.
282
What are producers?
Photosynthetic organisms at the start of the food chain that manufacture biomass for all living things.
283
What is a quadrat?
A square grid of known area used in sampling to determine the abundance of organisms in a habitat.
284
What is Rhizobium?
A type of nitrogen-fixing bacteria that lives inside the root nodules of leguminous plants.
285
What is succession?
Describes changes in the community of organisms occupying a certain area over time.
286
What does sustainable mean?
The ability to maintain something for future generations.
287
What is a sustainable resource?
A resource that can be continuously renewed; it will not diminish or run out.
288
What is a trophic level?
The position of an organism in a food chain.
289
What are alveoli?
Tiny air sacs that serve as the primary gaseous exchange surface. They consist of a thin epithelial cell layer, collagen and elastic fibres.
290
What is breathing rate?
The number of breaths per minute.
291
What are bronchi?
Divisions of the trachea that lead into the lungs. They are small tubes supported by incomplete rings of cartilage.
292
What are bronchioles?
Many small divisions of the bronchi. They contain smooth muscle to restrict airflow to the lungs but do not have cartilage. They are lined with a thin layer of ciliated epithelial cells.
293
What is cartilage?
Strong, flexible connective tissue that supports the walls of the trachea and bronchi, preventing collapse. It is found in an incomplete ring shape.
294
What are ciliated epithelial cells?
Specialised cells with tiny hair-like cilia found lining the trachea that waft bacteria-containing mucus up to the back of the throat, where it is swallowed.
295
What is countercurrent flow?
An adaptation for gaseous exchange in bony fish. Blood in the gill filaments and water moving over the gills flow in opposite directions, maintaining a steep oxygen concentration gradient.
296
What are elastic fibres?
Fibres of elastin that allow the alveoli to stretch as air is drawn in and recoil back to normal size, expelling air. They are also found in the trachea, bronchi and bronchioles.
297
What is an exchange surface?
A surface over which materials are exchanged from one region to another. An effective exchange surface has a large surface area, thin layers, a good blood supply, and ventilation to maintain a steep diffusion gradient.
298
What happens during expiration?
During expiration (exhalation) the diaphragm relaxes and reverts to a dome. The external intercostal muscles relax, moving the ribs down and in. The volume of the thorax decreases and thoracic pressure exceeds air pressure. Air moves out of the trachea.
299
What are gill filaments?
The main site of gaseous exchange in fish, over which water flows. They are found in large stacks, known as gill plates, and have gill lamellae which provide a large surface area for exchange.
300
What are gill lamellae?
The fine branches of the gill filaments. They are adapted for gaseous exchange by having a large surface area and good blood supply.
301
What are gill plates?
Large stacks of gill filaments.
302
What are gills?
The organs of gaseous exchange in fish. They are contained in a gill cavity and are made up of gill lamellae, gill filaments and gill plates.
303
What are goblet cells?
Specialised cells that secrete mucus onto the trachea lining. The mucus traps harmful substances and microorganisms, preventing their entry into the lungs.
304
What happens during inspiration?
During inspiration (inhalation) the diaphragm contracts and flattens and the external intercostal muscles contract, moving the ribs up and out. The volume of the thorax increases and thoracic pressure falls below air pressure. Air moves into the trachea.
305
What are internal intercostal muscles?
Muscles found between the ribs which are responsible for forced exhalation.
306
What is the mammalian gaseous exchange system?
A complex system found in mammals in which oxygen and carbon dioxide gases are exchanged.
307
What is an operculum?
A flap that covers the gills of bony fish. It protects the gills and helps to maintain a constant stream of water over them.
308
What is smooth muscle?
An involuntary muscle found in the walls of the trachea and bronchi. It constricts the lumen of the bronchi by contracting, reducing airflow to the lungs.
309
What are spiracles?
Small, external openings along the thorax and abdomen of most insects, through which air enters, and air and water leave the gaseous exchange system. Spiracle sphincters open and close the spiracles to control gas exchange.
310
What is a spirometer?
A device used to examine patterns of breathing and determine different aspects of lung volume.
311
What is the surface area to volume ratio?
The surface area of an object divided by its volume. The larger the surface area to volume ratio, the smaller the object.
312
What is tidal volume?
The volume of air that moves into and out of the lungs during a normal breath.
313
What is the trachea in mammals?
The primary airway which carries air from the nasal cavity down into the chest. It is a tube supported by incomplete rings of cartilage.
314
What are tracheae in insects?
Large tubes that run from the spiracles, into and along an insect’s body. They are supported by spirals of chitin. The tracheae divide further into smaller tracheoles.
315
What is tracheal fluid?
A fluid found at the ends of the tracheoles. The amount of fluid affects the surface area available for gaseous exchange and water loss.
316
What are tracheoles?
Divisions of the tracheae that run throughout the tissues of an insect, forming a complex network. They are the main site of gas exchange and are completely permeable to gases.
317
What is ventilation?
The movement of fresh air into the lungs and stale air out of the lungs via inspiration and expiration.
318
What is vital capacity?
The largest volume of air that can be breathed in following the strongest possible exhalation.
319
What is affinity?
The tendency of one substance to bind with another substance.
320
What is the aorta?
The artery that takes oxygenated blood away from the heart to the body.
321
What is an arteriole?
A type of blood vessel that connects the arteries and capillaries. The walls of the arterioles contain large amounts of smooth muscle, some elastic fibres and some collagen.
322
What is an artery?
A type of blood vessel that carries blood away from the heart to the tissues, under high pressure. The walls of the arteries contain collagen, smooth muscle and elastic fibres.
323
What is atrial fibrillation?
An arrhythmia that involves the rapid contraction of the atria, preventing complete ventricular filling.
324
What is atrial systole?
The stage of the cardiac cycle in which the atria contract, pushing blood into the ventricles. The AV valves are pushed open fully and the atria are emptied of blood.
325
What is the atrioventricular node (AVN)?
A group of cells located between the atria that slow down the wave of excitation and pass it between the ventricles, along the bundle of His.
326
What are atrioventricular (AV) valves?
The valves found between the atria and ventricles. They prevent the backflow of blood from the ventricles into the atria. There are two types of atrioventricular valves: bicuspid and tricuspid.
327
What are bicuspid valves?
The atrioventricular valves found between the left atrium and left ventricle.
328
What is blood?
The transport medium in the mammalian circulatory system. It consists of plasma, red blood cells, white blood cells and platelets.
329
What is the Bohr effect?
The loss of affinity of haemoglobin for oxygen as the partial pressure of carbon dioxide increases.
330
What is bradycardia?
A slow resting heart rate below 60 bpm.
331
What is the bundle of His?
A collection of Purkyne fibres which run from the AVN down to the apex of the ventricles.
332
What are capillaries?
Microscopic blood vessels that form a large network through the tissues of the body and connect the arterioles to the venules. They are the site of exchange of substances between the blood and the tissues.
333
What is carbonic anhydrase?
An enzyme that catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid.
334
What is the cardiac cycle?
Describes the sequence of events involved in one complete contraction and relaxation of the heart. There are three stages: atrial systole, ventricular systole and diastole.
335
What is cardiac output?
The volume of blood pumped by the heart through the circulatory system in one minute. It is calculated using the equation: cardiac output = heart rate × stroke volume.
336
What is the chloride shift?
The process by which chloride ions move into the erythrocytes in exchange for hydrogen carbonate ions which diffuse out of the erythrocytes. This maintains the electrochemical equilibrium of the cell.
337
What is the circulatory system?
The transport system in animals.
338
What is a closed circulatory system?
A circulatory system in which the blood pumped by the heart is contained within blood vessels. The blood does not come into direct contact with the cells. Closed circulatory systems are found in animals, e.g. vertebrates.
339
What is diastole?
The stage of the cardiac cycle in which the heart muscle relaxes. The atria and ventricles fill with blood.
340
What is a double circulatory system?
A circulatory system in which the blood flows through the heart twice in two circuits. Blood is pumped from the heart to the lungs before returning to the heart. It is then pumped around the body, after which it returns to the heart again. Double circulatory systems are found in mammals.
341
What is an ectopic heartbeat?
Additional heartbeats outside of the normal heart rhythm.
342
What is an electrocardiogram (ECG)?
A technique used to indirectly measure the spread of electrical activity through the heart by measuring tiny changes in the skin's electrical conductivity. This produces a trace which is used to detect abnormalities in heart rhythm.
343
What is haemoglobin?
The red pigment found in erythrocytes that binds reversibly with four oxygen molecules to form oxyhaemoglobin. It is a globular protein that consists of four polypeptide chains, each with a prosthetic haem group.
344
What is haemoglobinic acid?
The product formed when haemoglobin accepts free hydrogen ions. This enables haemoglobin to act as a buffer, reducing changes in blood pH.
345
What is heart rate?
The number of times the heart beats in one minute.
346
What is hydrostatic pressure?
The pressure exerted on the sides of a vessel by a fluid.
347
What is the inferior vena cava?
The vein that returns deoxygenated blood to the heart from the lower body.
348
What is lymph?
Modified tissue fluid that drains into the lymphatic system. It carries less oxygen and fewer nutrients than tissue fluid, but also contains fatty acids.
349
What is myogenic?
Describes cardiac muscle tissue that initiates its own contraction, without outside stimulation from nervous impulses.
350
What is oncotic pressure?
The movement of water into the blood by osmosis due to the tendency of plasma proteins to lower the water potential of the blood.
351
What is an open circulatory system?
A circulatory system in which the transport medium pumped by the heart is not contained within vessels, but moves freely. The transport fluid comes into direct contact with the cells. Open circulatory systems are found in invertebrates, e.g. insects.
352
What is the oxygen dissociation curve?
A graph that describes the relationship between the partial pressure of oxygen and the percentage saturation of haemoglobin in the blood.
353
What is plasma?
The main component of the blood that carries red blood cells. It is a yellow liquid that contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste.
354
What are pulmonary arteries?
The arteries that carry deoxygenated blood away from the heart to the lungs.
355
What are pulmonary veins?
The veins that carry oxygenated blood from the lungs to the heart.
356
What is Purkyne tissue?
Specialised cardiac muscle fibres which make up the bundle of His and conduct the wave of excitation through the septum, from the AVN down to the apex of the ventricles.
357
What are semilunar valves?
A pair of valves found between the ventricles and arteries. They prevent the backflow of blood from the arteries into the ventricles.
358
What is the septum?
The wall of muscle which separates the left side of the heart from the right side of the heart, preventing oxygenated and deoxygenated blood from mixing.
359
What is a single circulatory system?
A circulatory system in which the blood travels one circuit; blood flows through the heart and is pumped around the body before returning to the heart. Single circulatory systems are found in fish.
360
What is the sinoatrial node (SAN)?
A group of cells in the wall of the right atrium that generate electrical activity, causing the atria to contract. The SAN is often referred to as the heart’s pacemaker.
361
What is stroke volume?
The volume of blood pumped by the left ventricle of the heart in a single contraction.
362
What is the superior vena cava?
The vein that returns deoxygenated blood to the heart from the head and upper body.
363
What is tachycardia?
A rapid resting heart rate over 100 bpm.
364
What is tissue fluid?
The fluid that surrounds the cells of animals. It has the same composition of plasma but does not contain red blood cells or plasma proteins.
365
What are tricuspid valves?
The atrioventricular valves found between the right atrium and right ventricle.
366
What is a vein?
A type of blood vessel that carries blood towards the heart under low pressure. They have a wide lumen, a smooth inner lining and valves. The walls of the veins contain large amounts of collagen, smooth muscle and little elastic fibre.
367
What is ventricular systole?
The stage of the cardiac cycle in which the ventricles contract, pushing blood into the arteries. The semi-lunar valves are pushed open fully.
368
What is a venule?
A type of blood vessel that connects the capillaries and veins. The walls of the venules contain small amounts of collagen and smooth muscle.
369
What is active loading?
The process by which hydrogen ions are actively pumped out of companion cells using ATP, before diffusing down a concentration gradient, back into the cells via co-transporter proteins, whilst carrying sucrose.
370
What is adhesion in water movement?
The formation of hydrogen bonds between carbohydrates in the xylem vessel walls and water molecules. This contributes to the capillarity of water and transpiration pull.
371
What is the apoplast route?
One of two pathways by which water and minerals move across the root. Water moves through intercellular spaces between cellulose molecules in the cell wall.
372
What is the Casparian strip?
A waterproof strip surrounding the endodermal cells of the root that blocks the apoplast pathway, forcing water through the symplast route.
373
What is cohesion in water movement?
The formation of hydrogen bonds between water molecules. This contributes to the capillarity of water and transpiration pull.
374
What is the cohesion-tension theory?
The model that explains the movement of water from the soil to the leaves, in a continuous stream.
375
What are companion cells?
The active cells of the phloem located adjacent to the sieve tube elements. They retain their nucleus and organelles, producing ATP for metabolic processes in both themselves and the sieve tube elements.
376
What are dicotyledonous plants?
Plants that produce seeds that contain two cotyledons. They have two primary leaves.
377
What are hydrophytes?
Plants that are adapted to live and reproduce in very wet habitats, e.g. water lilies.
378
What is phloem?
A living plant transport vessel responsible for the transfer of assimilates to all parts of the plant. The phloem consists of sieve tube elements and companion cells.
379
What are plasmodesmata in phloem?
Small pores between adjacent sieve tube elements and companion cells that allow communication and the exchange of materials.
380
What is a potometer?
An apparatus used to measure water uptake from a cut shoot.
381
What are root hair cells?
Specialised cells responsible for the uptake of water and minerals from the soil. They have long hair-like extensions known as root hairs, which are adapted as exchange surfaces.
382
What are sieve plates?
The perforated end walls of sieve tube elements that allow plant assimilates to flow between cells unimpeded.
383
What are sieve tube elements?
The main cells of the phloem. They are elongated cells.
384
What are small pores between adjacent sieve tube elements and companion cells?
They allow communication and the exchange of materials.
385
What are sieve tube elements?
The main cells of the phloem. They are elongated cells laid end-to-end with sieve plates between and contain few organelles.
386
What are sinks in plants?
The regions of a plant that remove assimilates, e.g., roots, meristem, fruits.
387
What are sources in plants?
The regions of a plant that produce assimilates, e.g., leaves, storage organs.
388
What is the symplast route?
One of two pathways by which water and minerals move across the root. Water enters the cytoplasm through the plasma membrane and moves between adjacent cells via plasmodesmata.
389
What is translocation?
The movement of organic compounds in the phloem, from sources to sinks.
390
What is transpiration?
Water loss from plant leaves and stems via diffusion and evaporation. The rate of transpiration is affected by light, temperature, humidity, air movement and soil-water availability.
391
What is the transpiration stream?
The flow of water from the roots to the leaves in plants, where it is lost by evaporation to the environment.
392
What is a vascular bundle?
The vascular system in herbaceous dicotyledonous plants, consisting of two transport vessels, the xylem and the phloem.
393
What is a vascular system?
A network of transport vessels in animals and plants.
394
What are xerophytes?
Plants that are adapted to live and reproduce in dry habitats where water availability is low, e.g., cacti and marram grass.
395
What is xylem?
A non-living plant transport vessel responsible for the transfer of water and minerals from the roots to the shoots and leaves.
396
What is abscisic acid (ABA)?
A plant hormone that stimulates stomatal closing, maintains seed dormancy, and triggers cold protective responses.
397
What is abscission?
The shedding of leaves in plants.
398
What is acetylcholine?
A type of neurotransmitter that is used for communication between neurones.
399
What is actin?
A type of protein filament found in myofibrils, forming thin filaments consisting of two long twisted chains.
400
What is the actin-myosin binding site?
A site on actin that is normally blocked by tropomyosin, which becomes exposed during muscle contraction.
401
What is an actin-myosin cross-bridge?
The cross-bridge formed when a myosin head attaches to the myosin binding site on an actin filament.
402
What is adenylyl cyclase?
An enzyme that catalyses the conversion of ATP to cAMP.
403
What are adrenal glands?
Glands located on the top of the kidneys that produce adrenaline and steroid hormones.
404
What is adrenaline?
A hormone secreted by the adrenal glands under stressful conditions, serving as a ‘primary messenger’.
405
What is an afferent arteriole?
The larger diameter arteriole that carries blood to the glomerulus for ultrafiltration.
406
What are alkaloids?
A group of nitrogenous compounds found in plants that affect the metabolism of animals or insects.
407
What is the all-or-nothing principle?
The principle that describes how any generator potential reaching or exceeding the threshold potential produces an action potential of equal magnitude.
408
What are alpha cells (α cells)?
Cells in the pancreas that secrete glucagon into the blood to raise glucose concentration.
409
What are anisotropic (A) bands?
The darker bands in a myofibril, consisting of overlapping actin and myosin filaments.
410
What are anabolic steroids?
A class of performance-enhancing drugs structurally similar to testosterone, used illegally by athletes.
411
What is the anterior pituitary gland?
The region of the pituitary gland that produces and secretes hormones.
412
What is antidiuretic hormone (ADH)?
A hormone released from the posterior pituitary gland that increases the reabsorption of water in the kidney tubules.
413
What is aquaporin?
A membrane channel used for the selective transport of water in and out of the cell.
414
What is the autonomic nervous system?
A branch of the nervous system that carries nerve impulses to muscles and glands, controlling involuntary activities.
415
What are auxins?
A class of plant hormones that control cell elongation, produce tropisms, and prevent abscission.
416
What is an axon?
An extension from a nerve cell that carries impulses away from the cell body.
417
What are beta cells (β cells)?
Cells in the pancreas that secrete insulin into the blood to lower glucose concentration.
418
What are bile canaliculi?
Vessels that collect bile produced by hepatocytes.
419
What is the blinking reflex?
The involuntary blinking of the eyelid when an object is held close to the eye.
420
What is cardiac muscle?
A myogenic muscle found in the walls of the heart.
421
What is the central nervous system (CNS)?
The brain and spinal cord.
422
What is the cerebellum?
The region of the brain that controls muscle coordination and non-voluntary movement.
423
What is the cerebrum?
The largest region of the brain responsible for voluntary and some involuntary responses.
424
What is a cholinergic synapse?
A synapse that uses the neurotransmitter acetylcholine.
425
What is creatine phosphate?
A compound stored in muscles that serves as a phosphate reserve for ATP regeneration.
426
What is cutting?
A small section of the root or stem of an adult plant.
427
What is cyclic AMP (cAMP)?
A ‘second messenger’ involved in the action of adrenaline that activates protein kinase.
428
What is a dendron?
An extension from a nerve cell that carries impulses towards the cell body.
429
What is depolarisation?
The rapid influx of sodium ions into the cell, causing it to lose its negative charge.
430
What is an ectotherm?
An organism dependent on its environment to maintain its body temperature.
431
What is an effector?
An organ, tissue, or cell that produces a response to a stimulus.
432
What is an efferent arteriole?
The smaller diameter arteriole that carries blood away from the glomerulus after ultrafiltration.
433
What is endocrine signalling?
A type of signalling that uses hormones secreted by endocrine cells into the blood.
434
What is an endotherm?
An organism that can regulate its own body temperature without relying on external heat sources.
435
What is ethene?
A plant hormone that stimulates the ripening of fruit and promotes abscission.
436
What is an excitatory postsynaptic potential (EPSP)?
An impulse that stimulates an action potential in the postsynaptic neurone.
437
What is excretion?
The process of removing metabolic waste from an organism.
438
What is the fight or flight response?
The physiological reaction of the body in response to a potentially dangerous situation.
439
What is geotropism?
A plant’s growth response to gravity.
440
What are gibberellins?
Plant hormones that control stem elongation and trigger the growth of the pollen tube.
441
What is the glomerular filtration rate (GFR)?
A method of measuring kidney function assessing the amount of blood plasma filtered per unit of time.
442
What is a glomerulus?
The bundle of blood vessels at the beginning of a kidney nephron where ultrafiltration takes place.
443
What is haemodialysis?
A type of dialysis where a patient’s blood is fed into a dialysis machine to remove waste.
444
What is the hepatic artery?
The main artery supplying the liver tissue with oxygenated blood from the heart.
445
What is the hepatic portal vein?
The main vein carrying blood rich in nutrients from the small intestine and pancreas to the liver.
446
What is the hepatic vein?
The main vein taking deoxygenated blood away from the liver back to the heart.
447
What is homeostasis?
Maintaining a constant internal environment around an optimum despite external change.
448
What are hormonal weedkillers?
Hormones that alter plant metabolism, promoting rapid growth that is unsustainable.
449
What are hormones?
Cell signalling molecules produced by endocrine glands that travel to target cells.
450
What is hyperpolarisation?
The drop in membrane potential below the resting potential after repolarization.
451
What is the hypothalamus?
The region of the brain that serves as the control centre for the autonomic nervous system.
452
What is the H-zone?
The lighter region in the centre of each A band in a myofibril.
453
What is an inhibitory postsynaptic potential (IPSP)?
An impulse that inhibits the next neurone from generating an action potential.
454
What are the Islets of Langerhans?
Regions of the pancreas containing α and β cells.
455
What are isotropic (I) bands?
The lighter bands in a myofibril, consisting of non-overlapping actin and myosin filaments.
456
What is the knee-jerk reflex?
A type of spinal reflex involving the sudden involuntary movement of the lower leg.
457
What is a Kupffer cell?
A specialized type of macrophage located in the liver that removes pathogens and dead cells.
458
What is the loop of Henle?
A large hairpin shaped loop in the kidney tubule used to regulate water and salt concentration.
459
What is negative tropism?
The growth of a plant away from a stimulus.
460
What are neurotransmitters?
Chemicals used for communication between neurones and their target cells.
461
What is the medulla oblongata?
The region of the brain that regulates autonomic activities such as ventilation and heart rate.
462
What is metabolic waste?
Products produced in metabolic reactions that have no benefit to the organism.
463
What is Mimosa pudica?
A plant that exhibits rapid leaf-folding in response to touch as a protective mechanism.
464
What are monoclonal antibodies?
Antibodies produced by plasma cells that are identical clones of the same parent cell.
465
What is a motor neurone?
A neurone that carries nerve impulses from the CNS to the effectors.
466
What is myelination?
The formation of a myelin sheath around nerve cells by Schwann Cells.
467
What are myofibrils?
Tiny contractile muscle fibres that group together to form muscles.
468
What is myogenic?
Describes cardiac muscle tissue that initiates its own contraction.
469
What is myosin?
A type of protein filament found in myofibrils, forming thick filaments with bulbous heads.
470
What is negative feedback?
The product of a process that counteracts change to maintain equilibrium.
471
What is a neuromuscular junction?
An excitatory synapse formed between a motor neurone and a muscle fibre.
472
What are nodes of Ranvier?
Unmyelinated sections of nerve cells that allow for the propagation of an action potential.
473
What is an osmoreceptor?
A type of receptor in the hypothalamus that detects water concentration in blood plasma.
474
What is a Pacinian corpuscle?
A type of sensory receptor that detects changes in pressure on the skin.
475
What is the pancreas?
An organ with both exocrine and endocrine functions involved in digestion and blood glucose control.
476
What is paracrine signalling?
A type of signalling occurring between adjacent cells.
477
What is the parasympathetic nervous system?
A branch of the autonomic nervous system that is active under normal, resting conditions.
478
What is the peripheral nervous system (PNS)?
Pairs of nerves that originate from the CNS and carry nerve impulses into and out of the CNS.
479
What is peritoneal dialysis?
A type of dialysis where fluid is placed inside the abdomen to remove waste substances.
480
What are pheromones?
Cell-signalling molecules produced by an organism that affect the social behaviour of others.
481
What is photoperiodism?
A plant’s growth response to seasonal changes in the length of daylight.
482
What is phototropism?
A plant’s growth response to light.
483
What is the pituitary gland?
A small, hormone-producing gland located at the base of the brain.
484
What is positive feedback?
A process that causes an increase in change away from the normal.
485
What is positive tropism?
The growth of a plant towards a stimulus.
486
What is the posterior pituitary gland?
The region of the pituitary gland that stores and secretes hormones produced by the hypothalamus.
487
What is a postsynaptic neurone?
The neurone after the synapse that contains specific receptor proteins.
488
What is a presynaptic neurone?
The neurone before the synapse that releases neurotransmitters into the synaptic cleft.
489
What is a receptor?
A specialized structure that detects a specific type of stimulus.
490
What is a reflex?
A rapid, automatic response to a sensory stimulus by the body.
491
What is a reflex arc?
The pathway of neurones involved in a reflex action.
492
What is a relay neurone?
A neurone located in the spinal cord that links the sensory neurone to the motor neurone.
493
What is resting potential?
The potential difference across the cell membrane of a neurone at rest, typically between -60 and -70 mV.
494
What is rooting powder?
A hormone powder applied to cuttings that increases root formation.
495
What is saltatory conduction?
The setting up of localised circuits between nodes of Ranvier for rapid action potential propagation.
496
What is a sarcomere?
Each repeating unit of striations between adjacent Z-lines in a myofibril.
497
What is sarcoplasm?
The cytoplasm shared by muscle fibres, consisting of a high concentration of mitochondria.
498
What are Schwann cells?
Cells that form the myelin sheath around nerve cells in the peripheral nervous system.
499
What is the second messenger model?
The mechanism by which a hormone triggers the production of a second messenger inside a cell.
500
What is selective reabsorption?
The selective reuptake of useful substances along the kidney nephron.
501
What is a sensory neurone?
A neurone that carries nerve impulses from the receptors to the CNS.
502
What is a sinusoid?
A type of vessel in the liver formed from the convergence of the hepatic artery and portal vein.
503
What is skeletal muscle?
A voluntary muscle responsible for movement, attached to the skeleton by tendons.
504
What is the sliding filament theory?
The mechanism by which a muscle contracts, with myosin pulling actin to shorten the sarcomere.
505
What is smooth muscle?
An involuntary muscle found in the walls of blood vessels and organs.
506
What is the somatic nervous system?
A branch of the nervous system that carries impulses to the skeletal muscles.
507
What is summation?
The combination of many impulses that can cumulatively stimulate the generation of an action potential.
508
What is the sympathetic nervous system?
A branch of the autonomic nervous system that is active under stressful conditions.
509
What is a synapse?
The junction between two nerve cells or a nerve cell and an effector.
510
What are synaptic vesicles?
Secretory vesicles in the presynaptic neurone that store neurotransmitters.
511
What are tannins?
Phenols produced by many plants that serve as a chemical defence against herbivory.
512
What is the Ornithine Cycle?
The cycle of reactions responsible for producing urea.
513
What are synaptic vesicles?
Secretory vesicles located in the presynaptic neurone that store neurotransmitters. Upon fusion with the presynaptic membrane, their contents are released into the synaptic cleft.
514
What is the Ornithine Cycle?
The cycle of reactions responsible for producing urea from ammonia for detoxification and excretion.
515
What is tropism?
The growth response of a plant to a directional stimulus.
516
What is Type 1 diabetes?
An autoimmune disorder in which the beta cells are destroyed and the pancreas fails to produce sufficient insulin, characterised by uncontrolled high blood glucose levels.
517
What is Type 2 diabetes?
A type of diabetes where the body fails to produce enough insulin or when the pancreas no longer reacts to insulin, often caused by a poor diet and lack of exercise.
518
What is ultrafiltration?
The removal of small substances from the blood through the pressure created by the structure of the kidney nephron.
519
What is a Z-line?
The line in the centre of each I band.
520
What is acetyl coenzyme A?
A two-carbon molecule formed in oxidative decarboxylation when an acetyl group is bound by coenzyme A. It is oxidised in the Krebs cycle.
521
What is adenosine triphosphate (ATP)?
The universal energy carrier found in all living cells.
522
What is aerobic respiration?
A form of cellular respiration that takes place in the presence of oxygen and produces carbon dioxide, water, and ATP.
523
What is alcoholic fermentation?
A type of fermentation that takes place in plant root cells and yeast cells, producing ethanol and carbon dioxide.
524
What is anaerobic respiration?
A form of cellular respiration that takes place in the absence of oxygen, producing less ATP than aerobic respiration.
525
What is ATP synthase?
An enzyme found embedded in cellular membranes that phosphorylates ADP to form ATP as protons flow through it.
526
What is the Calvin cycle?
The light-independent reaction in photosynthesis.
527
What is the chemiosmotic theory?
The synthesis of ATP through the movement of protons down their concentration gradient across a semipermeable membrane, catalysed by ATP synthase.
528
What is chlorophyll?
A photosynthetic pigment located in the thylakoids of chloroplasts that absorbs light energy.
529
What is a chloroplast?
An organelle found in plants and algae that is the site of photosynthesis.
530
What is citrate?
A six-carbon molecule formed in the first stage of the Krebs cycle from the reaction of acetyl coenzyme A and oxaloacetate.
531
What is coenzyme A?
A coenzyme that binds an acetyl group to form acetyl coenzyme A during oxidative decarboxylation of aerobic respiration.
532
What are coenzymes?
Molecules that help enzymes carry out their function, e.g., NAD, FAD, coenzyme A, and NADP.
533
What are cristae?
Folds of the inner mitochondrial membrane that provide a large surface area for oxidative phosphorylation.
534
What is cyclic photophosphorylation?
The formation of ATP involving photosystem I only.
535
What is decarboxylation?
The removal of a carbon dioxide molecule.
536
What is dehydrogenation?
The removal of a hydrogen atom.
537
What is an electron acceptor?
Oxygen acts as the final electron acceptor in the electron transfer chain.
538
What are electron carriers?
Protein molecules that accept and release electrons, e.g., NAD, NADP.
539
What is the electron transport chain?
A series of electron carrier proteins that transfer electrons in a chain of oxidation-reduction reactions.
540
What is FAD?
A coenzyme that becomes reduced when it takes up hydrogen atoms during the Krebs cycle, forming reduced FAD.
541
What is fermentation?
A type of anaerobic respiration that does not involve an electron transport chain.
542
What is glycerate 3-phosphate (GP)?
A three-carbon molecule that is reduced by reduced NADP in the light-independent stage of photosynthesis to form two molecules of TP.
543
What is glycolysis?
An anaerobic process that takes place in the cytosol of the cell and breaks down glucose into two molecules of pyruvate.
544
What are grana?
Stacks of thylakoids connected by intergranal lamellae.
545
What is hexose bisphosphate?
The compound formed from the phosphorylation of glucose in glycolysis.
546
What is the inner mitochondrial membrane?
The mitochondrial membrane that segregates the matrix from the intermembrane space.
547
What is the intermembrane space?
The small space between the inner and outer mitochondrial membranes.
548
What is the Krebs cycle?
A series of oxidation-reduction reactions in the matrix of the mitochondria in which acetyl coenzyme A is oxidised.
549
What is lactate dehydrogenase?
An enzyme that catalyses the conversion of pyruvate to lactate.
550
What is lactate fermentation?
A type of fermentation that takes place in animal cells and produces lactate.
551
What are lamellae?
Membranous channels that connect adjacent grana in a chloroplast.
552
What is the light-dependent reaction?
The first stage of photosynthesis that uses light energy to produce ATP, reduced NADP, and oxygen.
553
What is the light-harvesting system?
A collection of protein and chlorophyll molecules found in the thylakoid membranes of chloroplasts.
554
What is the light-independent reaction?
The second stage of photosynthesis, also known as the Calvin cycle.
555
What is a limiting factor?
A variable that limits the rate of a particular reaction.
556
What is the link reaction?
Also known as oxidative decarboxylation.
557
What is the matrix?
The fluid-filled space within the inner membrane of the mitochondria.
558
What is a mitochondrion?
An organelle found in eukaryotic cells that is the site of aerobic respiration.
559
What is NAD?
A coenzyme that becomes reduced when it takes up hydrogen atoms during aerobic respiration.
560
What is NADP?
A coenzyme that becomes reduced when it takes up hydrogen atoms during the light-dependent stage of photosynthesis.
561
What is non-cyclic photophosphorylation?
The formation of ATP and reduced NADP involving both photosystems I and II.
562
What is the outer mitochondrial membrane?
The membrane segregating the contents of the mitochondrion from the rest of the cell.
563
What is oxaloacetate?
A four-carbon molecule that combines with acetyl coenzyme A to produce six-carbon citrate in the Krebs cycle.
564
What is oxidative decarboxylation?
The first stage of aerobic respiration that takes place in the mitochondrial matrix.
565
What is oxidative phosphorylation?
The synthesis of ATP from reduced coenzymes and oxygen in the electron transport chain of aerobic respiration.
566
What is photolysis?
The splitting of a molecule of water in the presence of light during the light-dependent stage of photosynthesis.
567
What is photophosphorylation?
The harnessing of light energy in photosynthesis to phosphorylate ADP, forming ATP.
568
What is photosynthesis?
A complex metabolic pathway that synthesises organic molecules in the presence of light.
569
What are photosynthetic pigments?
Molecules present in chloroplasts that absorb certain wavelengths of light.
570
What is a photosystem?
A protein complex involved in the absorption of light and transfer of electrons in photosynthesis.
571
What is pyruvate?
A three-carbon molecule produced in glycolysis.
572
What is the reaction centre?
The region of a photosystem where energy is funneled and photosynthetic reactions take place.
573
What is respiration?
A set of metabolic reactions that break down respiratory substances into smaller inorganic molecules.
574
What is the respiratory quotient (RQ)?
The ratio of carbon dioxide produced to oxygen consumed during respiration.
575
What is a respiratory substrate?
An organic molecule that can be broken down via the respiratory pathways to produce ATP.
576
What is a respirometer?
A device used to determine respiration rate in living organisms.
577
What is the retention value (Rf)?
Calculated using a specific equation.
578
What is ribulose bisphosphate (RuBP)?
A five-carbon compound that reacts with carbon dioxide in the light-independent stage of photosynthesis.
579
What is ribulose bisphosphate carboxylase (RuBisCO)?
An enzyme that catalyses the reaction of RuBP and carbon dioxide in the light-independent stage of photosynthesis.
580
What is the stroma?
The fluid interior of chloroplasts that contains the enzymes required for the light-independent reaction.
581
What is substrate-level phosphorylation?
The synthesis of ATP by the transfer of a phosphate group from a phosphorylated intermediate to ADP.
582
What is thin-layer chromatography (TLC)?
A technique used to separate photosynthetic pigments by their rate of movement when carried by a solvent.
583
What are thylakoids?
A series of flattened membrane-bound compartments in chloroplasts.
584
What is triose phosphate (TP)?
A three-carbon compound formed in glycolysis and the light-independent stage of photosynthesis.
