AQA GCSE Combined Science Trilogy key terms

The transfer of energy from radiation to the material it encounters.

The number of individuals of a species in an area, sometimes expressed per unit area.

The rate of change of velocity, measured in metres per second squared (m/s²).

A substance that produces hydrogen ions, $H^+$, in aqueous solution.

Rain made more acidic by air pollution, including sulphur dioxide released during fuel combustion.

A cap on the head of a sperm cell containing enzymes that help the sperm penetrate the egg’s outer layers.

The minimum energy that reacting particles must have for a collision to result in a reaction.

The region of an enzyme where a substrate binds and the reaction is catalysed.

The movement of substances against their concentration gradient, from a lower to a higher concentration, using energy released by respiration.

The number of nuclear decays occurring in a radioactive source per second, measured in becquerels (Bq). One becquerel means one decay per second.

A feature that enables an organism to survive in the conditions in which it normally lives.

A hormone released by the adrenal glands during fear or stress that increases heart rate and the delivery of oxygen and glucose to the brain and muscles.

A stem cell found in an adult animal that can replace cells and differentiate into a more limited range of cell types than an embryonic stem cell.

The use of microorganisms supplied with oxygen to break down organic matter in waste water.

Cellular respiration that uses oxygen to break down glucose completely, producing carbon dioxide and water.

The growing of crops, rearing of animals and management of biological resources to provide food, materials and fuels.

Acquired immunodeficiency syndrome: late-stage HIV infection in which the immune system is so badly damaged that it can no longer deal with other infections or cancers.

A frictional force acting on an object moving through air, opposing its movement through the air.

Organisms that can photosynthesise, many of which live in water. Early algae produced oxygen that began to accumulate in the atmosphere.

A soluble base that produces an alkaline solution in water, with a pH greater than 7.

A Group 1 metal whose atoms have one electron in their outer shell and form ions with a charge of $+1$ by losing that electron.

A saturated hydrocarbon containing only single bonds between carbon atoms.

An unsaturated hydrocarbon containing a carbon–carbon double bond, $\mathrm{C=C}$.

A version of a gene.

An immune reaction to a substance in the environment that is normally harmless.

A mixture of a metal with one or more other elements, which may be metals or non-metals.

A positively charged particle used to probe atomic structure in the gold-foil scattering experiment.