OCR GCSE Combined Science B key terms

A cell without a nucleus, with its main genetic material in the cytoplasm. Bacteria are prokaryotic.

A large biological molecule made from a chain of amino acids. Proteins have functions including growth, repair and enzyme action.

The process of making proteins by joining amino acids together in a particular order, using genetic instructions.

A particle in the nucleus with relative charge +1 and relative mass approximately 1.

The number of heartbeats per minute, measured by counting pulses in an artery.

A genetic diagram showing the possible combinations of alleles inherited from two parents.

A single element or compound that is not mixed with another substance.

A frame enclosing a known area, used to sample organisms such as plants.

Descriptive information, such as a colour change or the formation of a solid, rather than a numerical measurement.

A test that identifies whether a substance is present, rather than measuring its exact amount.

Numerical information, such as a measured mass, temperature or time.

A state in which radiation is absorbed and emitted at equal rates, so radiation causes no overall change in temperature.

The unwanted presence of radioactive material on or inside an object or person.

The random process in which an unstable atomic nucleus emits radiation and becomes more stable.

A radioactive isotope used to follow the movement or distribution of a substance, for example inside the body.

The spontaneous decay of unstable atomic nuclei, accompanied by the emission of radiation.

Treatment that uses ionising radiation to kill cancer cells or control their growth.

Unpredictable variation in measurements that causes readings to scatter above and below their expected value.

Selecting sample locations by chance rather than by the investigator's preference.

The largest value in a data set minus the smallest value. A range can also be stated by giving its minimum and maximum values.

A line drawn through a plotted position from the smallest to the largest repeat reading, showing their spread as an indication of uncertainty.

A region of a longitudinal wave where particles are further apart than usual.

A measure of change per unit time; water uptake rate is the volume of water absorbed divided by the time taken.

How much one quantity changes per unit change in another quantity, often per unit time.

The amount of photosynthesis taking place per unit time, estimated by measuring a change such as oxygen production or carbon dioxide uptake over a known time.

The amount of reactant used up or product formed per unit time.

A comparison of quantities in a stated order. For example, a carbon-to-hydrogen atom ratio of $1:2$ means twice as many hydrogen atoms as carbon atoms.

A graph showing how the energy changes as a reaction progresses from reactants to products.