Glossary

An A-Z of keywords and phrases, all of which are relevant to the post-16 biology curriculum.

 

A B C D E F G H I J K L M N O P Q R S T U V W Y Z
Decarboxylation

A chemical reaction that releases carbon dioxide (CO2).

Decomposition

The process by which organic matter decays or breaks down into less complex substances.

Dementia

A group of conditions characterised by memory loss and difficulty with thinking and problem solving.

Demography

The statistical study of a population. Characteristics often measured include birth rates and death rates (which can be used to calculate rates of population growth or decline) and the size of different age groups. These data are useful in evaluating and anticipating the occurrence of a disease in a population.

Dendrites

Protrusions from the cell body of a neuron that form branches connecting to other cells. These connections are input synapses, which receive signals from the axons of neighbouring neurons.

Dendritic cells

Phagocytic antigen-presenting cells (APCs) with an important role in alerting T cells to new pathogens. A type of white blood cell.

Depolarisation

The process of reducing the electrical potential of a cell or membrane, an essential part of the transmission of electrical impulses.

Desmosome

A cell junction involved in cell–cell connections via cadherin molecules and intermediate filaments.

Developmental psychology

The scientific study of how and why human beings change over the course of their lives. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, ageing and the entire lifespan.

Diabetes

A group of metabolic diseases caused by a lack of insulin production (type 1) or by the inability of the body to produce enough insulin or use it correctly (type 2).

Diaphragm

A muscle separating the thorax and abdomen that is used in breathing. When it contracts, the lungs inflate; when it relaxes, they deflate.

Differentiation

The process of a cell changing into a new cell type – usually from a less specialised cell type to a more specialised type during development.

Digestion

The process in which food is broken down physically (by the teeth or peristalsis movements of the gut) and chemically (by enzymes throughout the digestive tract) into molecules small enough to be absorbed by the body.

Diploid

A cell containing two complete sets of chromosomes, one from each parent.

DNA

Deoxyribonucleic acid, the chemical that carries genetic information. It is made up of two entwined strings (the ‘double helix’) of four chemical units (bases): A, T, G and C.

DNA methylation

An epigenetic mechanism in which methyl (CH3) groups are added to DNA to stop gene expression, allowing cells to switch certain genes off.

Doctorate

A qualification that involves conducting a piece of original research, usually at a university. These courses take at least three years, full-time. The best-known doctorate is a PhD or DPhil – short for Doctor of Philosophy. People with this qualification can be called ‘doctor’, but are not to be confused with medical doctors (who may also choose to take a PhD).

Domains of life

In the Woese classification system, organisms are separated into three domains of life – eukarya, bacteria and archaea – rather than the five kingdoms of life.

Dopamine

A neurotransmitter involved in the control of movement, posture and mood. L-DOPA (the precursor to dopamine and noradrenaline) is used to treat Parkinson’s disease.