OCR GCSE Biology A key terms

A short, unpaired stretch of bases at the end of a cut DNA fragment that can pair with a complementary end.

A detectable change in the internal or external environment.

A small pore in a leaf surface through which gases and water vapour can pass; plural: stomata.

Microscopic pores in the leaf surface through which gases and water vapour move.

A part of a cycle in which a substance is held, such as the atmosphere, an ocean, soil or living biomass.

One of the two long, continuous chains that form a DNA molecule.

The molecule that binds to an enzyme's active site and is changed during the reaction.

A simple carbohydrate molecule that can act as a building block for larger carbohydrates; glucose is an example.

The total area of the outside surfaces of an object, measured in squared units such as cm².

The amount of surface available compared with the volume of an object or cell.

A comparison of an object's surface area with its volume, usually simplified to the form $x:1$.

Water flowing over the land into streams, rivers, lakes and seas.

Everything outside the reacting system, from which energy can be transferred or to which energy can be transferred.

Fibres connecting the ciliary body to the lens; changes in their tension alter the lens's shape.

The ability to meet present needs without preventing future generations from meeting theirs.

A visible or measurable effect of a disease on its host.

A small gap between neurones across which a signal is transmitted using neurotransmitters.

The production of a larger or more complex molecule from smaller molecules.

The part of the circulation that carries blood between the heart and the rest of the body.

A cell that has a compatible receptor for a particular hormone and can therefore respond to it.

Treatment selected because a patient's cells or diseased cells possess a particular biological feature, often identified using genomic testing.

A tissue or organ containing cells that respond to a particular hormone.

A consumer that eats secondary consumers.

A hormone produced mainly by the testes that supports sperm production and causes some changes at puberty.

The regulation of body temperature within a suitable range despite internal or external changes.

A hormone released by the thyroid gland that stimulates the basal metabolic rate.

A group of specialised cells working together to perform a particular function.