Combined Science key terms

The pH at which an enzyme-catalysed reaction proceeds fastest under the conditions being investigated.

The temperature at which a process has its highest rate under the given conditions.

A factor of ten in the size of a quantity. A factor of $10^3$, or 1000, represents a difference of three orders of magnitude.

A rock containing metal or metal compounds from which a metal can be extracted.

A structure made of different tissues working together to carry out particular functions.

A structure inside a cell that performs a particular function, such as a mitochondrion or chloroplast.

Material originating from living organisms, such as faeces and food waste, which microorganisms can break down.

A single living individual.

A group of organs working together to carry out particular functions within an organism.

The pencil line on chromatography paper where the samples are placed before separation begins; also called the baseline.

A repeated change or back-and-forth movement about a central position.

An instrument that displays how an electrical signal changes with time; microphone signals can be used to measure sound arrival times.

The net movement of water through a partially permeable membrane from a dilute solution to a more concentrated solution.

Obtaining a shared, limited resource more successfully than another species, reducing the resources available to that species.

An electron in the outermost occupied shell of an atom. Outer electrons determine how an atom takes part in chemical reactions.

The outermost occupied electron energy level in an atom.

A result that is markedly different from the other results obtained under the same conditions.

The difference between the energy of the products and the energy of the reactants.

The release of an egg from an ovary.

The loss of electrons by a chemical species.

Gases made of nitrogen and oxygen, collectively written as $\mathrm{NO_x}$, that cause respiratory problems and contribute to acid rain.

Describes a substance that can support combustion, for example by providing oxygen, and make a fire more intense.

Blood containing oxygen that can be delivered to body cells for aerobic respiration.

(HT only) The amount of extra oxygen the body needs after exercise to react with accumulated lactic acid and remove it from the cells.

A group of cells in the right atrium that controls the natural resting heart rate.

A medicine that relieves pain, a symptom of disease, without killing the pathogens causing an infection.

Leaf tissue near the upper surface whose cells contain many chloroplasts for photosynthesis.