OCR GCSE Combined Science A key terms

A sub-cellular structure containing enzymes for aerobic respiration, which transfers energy from food for cell activities.

Division of the nucleus in which copied chromosomes are separated into two genetically identical sets.

A substance containing two or more substances that are not chemically bonded together and can be separated by physical methods.

The liquid or gas that moves through or over the stationary phase, carrying components of the mixture.

The value or category that occurs most frequently in a data set.

The mass per mole of a substance, usually expressed in $\mathrm{g\,mol^{-1}}$ in these calculations.

The SI unit of amount of substance, symbol mol. One mole contains exactly $6.022\,140\,76 \times 10^{23}$ specified elementary entities, such as atoms, molecules or ions.

A chemical formula showing the actual number of atoms of each element in one molecule.

The study of evolutionary relationships by comparing biological molecules, such as DNA.

A group of atoms chemically bonded together.

The ratio between the amounts in moles of substances reacting or being produced, given by the coefficients in a balanced chemical equation.

Melted into the liquid state by heating; this does not mean dissolved in water.

A quantity describing an object's motion, equal to its mass multiplied by its velocity. Momentum has direction and is measured in kg m/s.

Existing as individual atoms rather than molecules containing two or more atoms.

A small molecule that can join with other monomers to form a polymer.

The force experienced by a current-carrying conductor placed in a magnetic field, caused by the interaction of the magnetic fields.

A nerve cell that carries electrical impulses from the central nervous system to an effector.

A sticky substance produced by cells lining the airways that traps pathogens and other particles.

An organism made of many cells.

A change in the genetic material of a cell.

An interaction between two species in which both benefit.

A fatty insulating layer around a neurone fibre that increases the speed of impulse transmission.

A network of cables and transformers that transfers electrical energy from power stations to consumers.

A metal found naturally as the uncombined element rather than chemically combined in a compound.

Bacteria normally living in parts of the body, such as the gut and vagina, that can help protect against infection by competing with pathogenic bacteria.

A system that groups organisms according to their evolutionary relationships and common ancestry.

The process in which organisms with inherited characteristics better suited to their environment are more likely to survive, reproduce and pass those characteristics to their offspring.