WBCHSE HS Biological Science key terms

Folds of the inner mitochondrial membrane that increase surface area for the electron transport chain and ATP synthase, concentrating the machinery of aerobic respiration in a small organelle volume.

Movement of protons down an electrochemical gradient through ATP synthase, driving ATP formation. In mitochondria the gradient is built across the inner membrane; in chloroplasts it forms across the thylakoid membrane.

ATP production in mitochondria in which NADH and FADH2 pass electrons to oxygen via membrane carriers, and the released energy pumps protons to power ATP synthase.

Exchange of corresponding segments between non-sister chromatids of homologous chromosomes during prophase I of meiosis, producing new allele combinations on a single chromosome.

The visible point where two homologous chromosomes remain joined after crossing over, marking the site of genetic exchange; chiasmata also hold homologues together until anaphase I.

Percentage of offspring showing recombination between two linked genes; it rises with the distance separating them and is used to construct genetic maps in centimorgans.

Tendency of genes located close together on the same chromosome to be inherited together, so their alleles appear in parental combinations more often than independent assortment would predict.

Enzyme inhibition in which a molecule resembling the substrate occupies the active site, so more substrate can overcome it; maximum reaction rate is unchanged while substrate affinity appears reduced.

The small region of an enzyme where substrate binds and catalysis occurs, formed by a few amino acid residues brought together in the folded tertiary structure.

A binding site on an enzyme separate from the active site; binding of a regulator there changes the enzyme's shape and so switches its catalytic activity up or down.

Splitting of water molecules by light energy in photosystem II, releasing electrons to replace those lost by chlorophyll, plus protons and oxygen as by-products.

Formation of ATP in chloroplasts using light energy, either cyclic (electrons return to photosystem I) or non-cyclic (electrons pass from water to NADP+).

Light-independent stage of photosynthesis in the stroma where CO2 is fixed onto RuBP, reduced using ATP and NADPH, and rearranged to regenerate RuBP and release sugar.

Wasteful reaction in which RuBisCO binds oxygen instead of carbon dioxide, consuming ATP and releasing CO2; it increases in hot, dry conditions when stomata close.

Arrangement in C4 leaves where bundle-sheath cells with large chloroplasts are ringed by mesophyll cells, allowing CO2 to be concentrated before it reaches RuBisCO.

Arrangement in fish gills where water and blood flow in opposite directions across the lamellae, maintaining a diffusion gradient along the whole exchange surface.

Reduced affinity of haemoglobin for oxygen at low pH or high carbon dioxide, which shifts the dissociation curve right and improves oxygen unloading in active tissues.

The functional unit of the kidney, comprising a glomerulus, Bowman's capsule and a tubule in which filtration, selective reabsorption and secretion produce urine.

A chemical released from a presynaptic terminal into a synapse, where it binds receptors on the next cell and either excites or inhibits it; acetylcholine is one example.

Event unique to flowering plants in which one male gamete fuses with the egg to form the zygote and a second fuses with two polar nuclei to form triploid endosperm.

Nutritive tissue of the seed formed from the triploid fusion nucleus in angiosperms, supplying the developing embryo with food before or during germination.

Suppression of growth of lateral buds by the terminal bud, largely through auxin moving down the shoot; removing the apex releases the side buds.

Condition in which allele and genotype frequencies of a population stay constant from generation to generation, provided mating is random and no selection, mutation, migration or drift occurs.

Random change in allele frequencies between generations, especially strong in small populations, where chance loss of alleles can occur independently of natural selection.

Rapid diversification of one ancestral lineage into several species that occupy different niches, often after colonising a new habitat; Darwin's finches are the standard example.

Diagram showing numbers, biomass or energy at successive trophic levels; energy pyramids are always upright because energy is lost at each transfer.

Rate at which producers capture and store energy as organic matter in an ecosystem; net primary productivity equals gross productivity minus respiration losses.

Enrichment of water with nutrients such as nitrates and phosphates, causing algal blooms whose decay depletes dissolved oxygen and can kill fish.

Bacterial enzyme that cuts DNA at a specific recognition sequence, leaving sticky or blunt ends; it is a basic tool for inserting genes into vectors.

Small circular DNA molecule used to carry a foreign gene into a host cell, usually engineered with a selectable marker and a recognition site for a restriction enzyme.

Antibody of a single specificity produced by a clone of hybridoma cells, widely used in diagnosis and targeted therapy because it binds one epitope only.

Volumetric procedure in which a solution of known concentration is added from a burette until the end point is reached, allowing the unknown concentration to be calculated.

Instrument that measures how much light of a chosen wavelength is absorbed by a coloured solution, giving a value proportional to concentration via a calibration curve.

A comparison treatment identical to the test except for the single variable being changed, so that any measured difference can be attributed to that variable.