BW Abitur Biology Bilingual EN key terms

The separation of different biochemical processes inside membrane-bound organelles or regions of a cell, so that incompatible reactions can proceed at the same time and conditions such as pH can be optimised locally.

The description of a biomembrane as a fluid phospholipid bilayer with proteins, glycoproteins and cholesterol embedded in or attached to it, in which the components can move laterally.

Passive transport of a substance across a membrane through a channel or carrier protein, down its concentration gradient and without energy input from ATP.

Movement of ions or molecules against their concentration gradient by transport proteins that consume metabolic energy, for example the sodium-potassium pump that maintains the resting potential of neurons.

A protein (or occasionally an RNA molecule) that catalyses a biochemical reaction by lowering its activation energy, binding substrates specifically at an active site without being consumed in the reaction.

Reduction of enzyme activity by a molecule that resembles the substrate and binds to the active site, so that the inhibitor competes with the substrate; high substrate concentration can overcome it.

Control of enzyme activity by a molecule binding at a site other than the active site, changing the enzyme's conformation and thereby increasing or decreasing its catalytic rate.

The minimum energy that reactant molecules must possess before a chemical reaction can take place; enzymes accelerate reactions by reducing this barrier.

Adenosine triphosphate, the universal energy currency of cells; hydrolysis of its terminal phosphate bond releases usable energy for endergonic processes such as active transport and biosynthesis.

The first stage of cellular respiration, in which glucose is split in the cytosol into two molecules of pyruvate, with net production of two ATP and two NADH per glucose.

The three-carbon end product of glycolysis; it is oxidised and decarboxylated to acetyl-CoA, which enters the citrate cycle in the mitochondrial matrix when oxygen is available.

ATP synthesis at the inner mitochondrial membrane, driven by the proton gradient built by the electron transport chain using the reducing power of NADH and FADH2 and oxygen as final electron acceptor.

A difference in hydrogen ion concentration across a membrane, storing potential energy that can be used by ATP synthase to make ATP or by transport proteins to move substances.

The thylakoid membrane processes of photosynthesis in which light energy excites pigments, water is split to release oxygen, and ATP and NADPH are produced for carbon fixation.

The light-independent stage of photosynthesis in the chloroplast stroma, in which the enzyme Rubisco fixes carbon dioxide onto ribulose bisphosphate and the carbon is reduced to carbohydrate using ATP and NADPH.

One of the alternative versions of a gene at a given locus on a chromosome; diploid organisms normally carry two alleles, which may be identical (homozygous) or different (heterozygous).

The particular combination of alleles an organism carries for one or more genes, as distinct from the observable characteristics (phenotype) that result from it and its environment.

The principle that the two alleles of a gene separate during meiosis so that each gamete receives only one of them, giving predictable ratios in the offspring of a cross.

Synthesis of an RNA molecule from a DNA template by RNA polymerase, occurring in the nucleus of eukaryotic cells before the RNA is processed and exported.

Assembly of a polypeptide chain at the ribosome, in which the base sequence of mRNA is read in codons and matched to amino acids delivered by transfer RNA.

A permanent change in the DNA base sequence, such as a substitution, insertion or deletion, which may alter the protein produced and may be inherited if it occurs in germ cells.

A bacterial enzyme that cuts DNA at a specific recognition sequence, producing fragments with sticky or blunt ends that are used in cloning and in DNA fingerprinting.

An in vitro method that amplifies a chosen DNA sequence through repeated cycles of denaturation, primer annealing and extension by a heat-stable DNA polymerase.

A technique that separates charged molecules such as DNA fragments or proteins in a gel under an electric field, with smaller or more highly charged molecules migrating faster.

The electrical potential difference across the membrane of an unstimulated neuron, typically about minus 70 millivolts, maintained mainly by potassium leak channels and the sodium-potassium pump.

A rapid, self-propagating reversal of membrane potential in a neuron, caused by voltage-gated sodium channels opening followed by potassium channels, which carries a signal along the axon.

The specialised junction at which a neuron transmits a signal to another cell, usually by releasing neurotransmitter into a synaptic cleft where it binds receptors on the postsynaptic membrane.

A chemical messenger released from synaptic vesicles that diffuses across the synaptic cleft and binds to specific receptors, exciting or inhibiting the postsynaptic cell.

The chain of events by which an extracellular signal such as a hormone or light stimulus is converted into a specific intracellular response, often via receptors, second messengers and protein kinases.

The differential survival and reproduction of individuals that differ in heritable traits, so that alleles conferring greater fitness in a given environment increase in frequency over generations.

Any barrier that prevents members of two populations from interbreeding and producing fertile offspring, allowing them to diverge genetically and eventually form separate species.

Similarity of structures or gene sequences resulting from shared ancestry rather than convergent adaptation; homologous features provide evidence for common descent in phylogeny.

A branching diagram representing hypothesised evolutionary relationships among organisms, in which branch points indicate common ancestors and branch lengths may represent time or genetic change.

The maximum population size of a species that an ecosystem can sustain indefinitely given the available resources, often modelled as the plateau of logistic growth.

A position in a food chain defined by the number of energy-transfer steps from the primary producers, such as primary consumer or secondary consumer.

Nutrient enrichment of a water body, usually by nitrate and phosphate runoff, that causes excessive algal growth and later oxygen depletion when the algae decompose.

A molecule, often a protein or polysaccharide on a pathogen surface, that is recognised specifically by an antibody or T-cell receptor and can trigger an immune response.

A Y-shaped immunoglobulin protein secreted by plasma cells that binds specifically to an antigen, neutralising the pathogen or marking it for destruction.

A long-lived lymphocyte produced after exposure to an antigen that responds rapidly on later contact with the same antigen, providing the basis of immunological memory and vaccination.

In an experiment, the group that is treated identically to the experimental group except for the factor being tested, allowing observed effects to be attributed to that factor.

The extent to which repeated measurements or repeats of an experiment give consistent results; it is increased by larger sample sizes and careful standardisation of procedure.

A statistical relationship in which two variables change together; it does not by itself establish that one variable causes the other, since confounding factors may be responsible.