OCR GCSE Biology A key terms

The process in which the lens changes shape to focus light from objects at different distances onto the retina.

The minimum energy needed to begin a chemical reaction.

The region of an enzyme with a shape complementary to its substrate, where the reaction is catalysed.

The movement of substances against their concentration gradient across a membrane, using energy released by respiration.

An inherited feature that makes an organism better suited to a particular environment.

A hormone that increases the permeability of kidney tubules and collecting ducts to water, allowing more water to be reabsorbed into the blood.

A hormone released by the adrenal glands during fear or stress that prepares the body for rapid action.

A stem cell found in a developed body that normally differentiates into a limited range of related cell types.

Describes a process that occurs in the presence of oxygen.

Respiration that uses oxygen and breaks down glucose completely, producing carbon dioxide and water with a high ATP yield.

A resource used in agricultural production, such as seed, animal feed, water, fertiliser, pesticide, fuel, labour or machinery.

The amount of usable crop or animal product obtained from a given area or agricultural system.

Acquired immune deficiency syndrome, a late stage of HIV infection in which immune defence has been severely weakened.

An alternative version of a gene.

A version of a gene. Different alleles are genetic variants of that gene.

A small organic molecule that acts as a monomer from which proteins are built.

Describes a process that occurs without oxygen.

Respiration that does not use oxygen and breaks down glucose incompletely, giving a much lower ATP yield than aerobic respiration.

A substance that kills bacteria or stops them growing.

A medicine that kills bacteria or inhibits their growth; it does not work against viruses.

The ability of a bacterium to survive exposure to an antibiotic that would normally kill it or stop its growth.

A gene used to identify cells that have taken up DNA; an antibiotic resistance marker allows those cells to survive exposure to a particular antibiotic.

A protein made by lymphocytes that binds to a particular antigen.

A hormone that controls how much water is reabsorbed from the kidney tubules into the blood.

A molecule that an antibody can recognise and bind to; it may be on a cell or free in a body fluid.

A substance that kills microorganisms or prevents them from growing.

A substance that kills microorganisms or stops their growth.