JENPAS-UG key terms

The thin outer boundary of a cell, made of two layers of lipid molecules with proteins embedded in it, that controls which substances enter and leave.

A membrane-bound cell organelle that produces most of the cell's usable energy through aerobic respiration and contains its own small loop of DNA.

The movement of water molecules across a partially permeable membrane from a region of higher water concentration to one of lower water concentration.

The net movement of particles from a region of higher concentration to a region of lower concentration, driven by random molecular motion and not requiring energy input.

Movement of ions or molecules across a membrane against their concentration gradient using carrier proteins and energy released from ATP.

A protein that speeds up a specific biochemical reaction by lowering its activation energy, usually acting on one particular substrate at a shaped active site.

Loss of a protein's functional three-dimensional shape caused by heat, extreme pH or chemicals, which destroys enzyme activity and is usually irreversible.

The oxygen-requiring breakdown of glucose to carbon dioxide and water, releasing a large amount of energy that cells capture as ATP.

The first stage of respiration, in which one glucose molecule is split in the cytoplasm into two pyruvate molecules with a small net yield of ATP.

The process by which plants, algae and some bacteria use light energy to convert carbon dioxide and water into glucose, releasing oxygen as a by-product.

The green pigment inside chloroplasts that absorbs mainly red and blue light and transfers the captured energy to the reactions of photosynthesis.

A green plant cell organelle enclosed by a double membrane, containing stacks of thylakoid membranes where the light-dependent reactions of photosynthesis occur.

A type of cell division producing four genetically different haploid daughter cells, central to gamete formation and to generating genetic variation.

Nuclear division that produces two genetically identical daughter nuclei with the same chromosome number as the parent cell, used in growth and repair.

Describing a cell or nucleus that contains one complete set of chromosomes, as gametes do, rather than the paired sets found in body cells.

One of two or more alternative versions of the same gene, occupying the same position on homologous chromosomes and producing slightly different characteristics.

The particular combination of alleles an organism carries for a given gene, written as pairs of letters such as AA, Aa or aa.

The observable characteristics of an organism, resulting from the interaction between its genotype and the environment it develops in.

The process by which individuals with inherited features better suited to their environment survive and reproduce more, so those alleles become more common over generations.

The formation of new species, typically when populations become reproductively isolated so that they can no longer interbreed to produce fertile offspring.

The maintenance of a stable internal environment, such as constant body temperature or blood glucose concentration, despite changes in external conditions.

A control mechanism in which a change in a condition triggers a response that reverses that change, bringing the value back towards its normal set point.

A chemical messenger secreted by an endocrine gland into the blood, which travels to and acts on specific target cells bearing matching receptors.

The fixed neural pathway that produces an automatic, rapid response to a stimulus, typically passing from receptor through a sensory neurone, relay neurone and motor neurone to an effector.

The small gap between two neurones or between a neurone and a muscle, across which a chemical neurotransmitter diffuses to pass the impulse onward.

A specialised nerve cell that conducts electrical impulses, consisting of a cell body, dendrites and a long axon often wrapped in a fatty myelin sheath.

A Y-shaped protein produced by lymphocytes that binds specifically to an antigen on a pathogen or toxin, helping to neutralise or destroy it.

A molecule, usually a protein or polysaccharide on the surface of a cell or pathogen, that is recognised as foreign and can trigger an immune response.

Introducing weakened, inactivated or fragment antigens into the body so that memory cells form, giving rapid protection against later infection by the same pathogen.

The concentration of a solution expressed as the number of moles of solute dissolved in one litre of solution, with units of mol per litre.

The amount of substance containing exactly the number of elementary entities equal to the Avogadro constant, about 6.02 times ten to the twenty-third.

The mass of one mole of a substance in grams per mole, numerically equal to its relative molecular mass and used to convert between mass and moles.

A quantitative procedure in which a solution of known concentration is added from a burette until an indicator shows the reaction is complete, allowing an unknown concentration to be calculated.

A logarithmic scale from 0 to 14 expressing the hydrogen ion concentration of a solution, where values below 7 are acidic and above 7 alkaline.

A solution that resists large changes in pH when small amounts of acid or alkali are added, usually because it contains a weak acid and its conjugate base.

A chemical change in which a substance loses electrons, often observed as the gain of oxygen or the loss of hydrogen.

A chemical change in which a substance gains electrons, often observed as the loss of oxygen or the gain of hydrogen, and which always accompanies oxidation.

One of two or more compounds that share the same molecular formula but differ in how their atoms are arranged, giving them different properties.

A specific cluster of atoms within an organic molecule, such as hydroxyl, carboxyl or amino, that largely determines the molecule's chemical behaviour and reactivity.