60 of the Biology glossary’s terms, each with the part of the syllabus where you first meet it.
A protein of three subunits on the inner surface of the plasma membrane that is activated by a G protein-coupled receptor when GDP on its α subunit is replaced by GTP.
A transmembrane receptor made of one polypeptide crossing the membrane seven times, which transmits a signal into the cell by activating a G protein when its ligand binds.
The first growth phase of interphase, in which the cell grows, synthesises proteins and increases its number of organelles before DNA replication.
The second growth phase of interphase, after DNA replication, in which the cell grows further and prepares for mitosis.
A haploid sex cell (a sperm or an egg) that fuses with another gamete at fertilisation to form a zygote.
The uptake of one gas and release of another across a surface, by diffusion, such as the uptake of oxygen and loss of carbon dioxide in respiration.
A surface across which gases diffuse between an organism and its surroundings; it is permeable, thin, moist and has a large surface area.
A technique that separates DNA fragments (or proteins) by size by moving them through a gel in an electric field; smaller DNA fragments move further towards the positive electrode.
A section of DNA with a specific base sequence that codes for a polypeptide or a functional RNA molecule and influences a characteristic.
The deliberate alteration of the base sequence of DNA at a specific, chosen position in the genome, for example with CRISPR–Cas9.
The process by which the information in a gene is used to make a functional product, such as a polypeptide or RNA; it begins with transcription.
The transfer of alleles from one population to another when individuals or their gametes move between the populations and interbreed.
A technique for investigating the function of a gene by changing it so that it is inoperative, then observing the effect on the organism.
The tendency of alleles of genes on the same chromosome to be inherited together, so that they do not assort independently.
A change to the base sequence of a gene, by substitution, insertion or deletion of one or more nucleotides.
All the alleles of all the genes in an interbreeding population.
The set of rules by which the sequence of base triplets (codons) in mRNA specifies the sequence of amino acids in a polypeptide; it is almost universal.
A mating between two chosen parents, used to study the inheritance of characteristics or to produce offspring with a desired combination of alleles.
The variety of alleles and genes within a species, both within a population and between populations of that species.
Random change in allele frequencies in a population from one generation to the next, caused by chance differences in which individuals survive and reproduce; its effects are greatest in small populations.
Differences in the alleles and base sequences carried by individuals of a population or species; mutation is its original source.
The whole of the genetic information of an organism, consisting of the entire base sequence of its DNA (or RNA in some viruses).
The expression of only one allele of a gene, depending on whether it was inherited from the mother or the father, because epigenetic tags from one parent are not removed in the gametes.
The combination of alleles of a gene (or genes) that an organism has inherited.
A group of closely related species that share many features and a recent common ancestor; the first part of a binomial name.
Reproductive isolation of populations caused by a physical barrier, such as a mountain range, river or sea, that prevents individuals from meeting and interbreeding.
A cell that gives rise to gametes, or a gamete itself; mutations in germ cells can be inherited by offspring.
The theory that many diseases are caused by microorganisms (germs) that invade the body and can be passed from one person to another.
The development of a seed into a seedling, starting with the uptake of water and ending when the young plant can photosynthesise.
A phytohormone, made mainly in young leaves and seeds, that promotes stem elongation, seed germination and, in some species, flowering.
The gas exchange organ of a fish, made of filaments with thin lamellae and many capillaries, ventilated by a one-way flow of water.
A protein folded into a compact, rounded shape, usually soluble in water, such as an enzyme, insulin or haemoglobin.
A knot of capillaries inside Bowman's capsule, supplied by a wide afferent arteriole and drained by a narrower efferent arteriole, where blood plasma is filtered under high pressure.
A hormone secreted by the alpha cells of the islets of Langerhans when blood glucose concentration falls; it stimulates liver cells to break down glycogen to glucose and release it into the blood.
A glucose transporter protein of muscle and fat cells, stored in vesicles and moved to the plasma membrane in response to insulin, so that glucose enters by facilitated diffusion.
GP, the three-carbon compound formed when RuBP combines with CO₂; it is reduced to triose phosphate using ATP and reduced NADP.
A small three-carbon molecule with a hydroxyl group on each carbon, which forms ester bonds with fatty acids to make triglycerides and phospholipids.
The energy storage polysaccharide of animals and fungi, made of α-glucose with 1,4 and 1,6 glycosidic bonds; more highly branched than amylopectin, stored in liver and muscle.
The synthesis of glycogen from glucose, carried out in liver and muscle cells and stimulated by insulin.
The hydrolysis of glycogen to glucose, carried out in liver cells when stimulated by glucagon (and in muscle cells for their own use).
A lipid with a carbohydrate chain attached, found in the outer layer of the plasma membrane with the carbohydrate facing outside the cell; involved in cell recognition and adhesion.
The first stage of cell respiration, in the cytoplasm: glucose is converted by phosphorylation, lysis, oxidation and ATP formation into two pyruvate, with a net yield of 2 ATP and 2 reduced NAD.
A protein with one or more carbohydrate chains covalently attached; in the plasma membrane the carbohydrate faces outwards and functions in cell recognition and adhesion.
The covalent bond formed by a condensation reaction between two monosaccharides, linking them through an oxygen atom.
The addition of carbohydrate chains to a protein (or lipid), which takes place in the rough ER and Golgi apparatus and produces glycoproteins.
The range of distances from a star within which a planet's surface temperature allows water to exist as a liquid; also called the habitable zone.
A stack of flattened, curved membrane sacs (cisternae) that receives proteins from the rough ER in vesicles, modifies and sorts them, and sends them out in new vesicles.
A peptide hormone (GnRH) secreted by cells of the hypothalamus that stimulates the anterior pituitary gland to secrete FSH and LH.
An instrument with two hinged arms and a protractor scale, used to measure the angle and range of motion of a joint.
A bacterium with a thick cell wall of peptidoglycan and no outer membrane, which stains purple with the Gram stain; Bacillus and Staphylococcus are examples.
A stack of thylakoids in a chloroplast; grana are joined to each other by unstacked thylakoid membranes called intergranal lamellae.
A biome with low to moderate rainfall and a dry season, dominated by grasses, with few trees because of drought, fire and grazing; includes temperate grassland and savanna.
A directional growth response to gravity; roots grow downwards (positive gravitropism) and shoots grow upwards (negative gravitropism).
The rise of free oxygen in Earth's atmosphere about 2.4 billion years ago, caused by oxygen released by photolysis in cyanobacteria.
The warming of the Earth's surface and lower atmosphere because greenhouse gases absorb long-wave infrared radiation emitted by the surface and re-emit some of it back towards the surface.
A gas in the atmosphere, such as water vapour, carbon dioxide, methane or nitrous oxide, that absorbs and re-emits long-wave infrared radiation, contributing to the greenhouse effect.
Nervous tissue made mainly of the cell bodies, dendrites and synapses of neurons, where information is integrated; it forms the cerebral cortex and the central part of the spinal cord.
A purine base (G) found in DNA and RNA, which pairs with cytosine by three hydrogen bonds.
One of a pair of cells surrounding a stoma that change shape to open or close it, controlling gas exchange and water loss.
An RNA molecule with about 20 bases complementary to a target DNA sequence, which binds to Cas9 and directs it to cut at that sequence.