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



Gene that codes for the peroxisomal membrane transporter protein, which mediates the import of very-long-chain fatty acids (VLCFAs) across the peroxisomal membrane for degradation.



Abscisic acid

A plant growth factor/hormone produced in parched leaves, roots and developing seeds that causes stomata to close (to save water) as well as seed dormancy.


Relating to higher education and study. For example, a researcher at a university may be described as an academic, or as working in academia.

Acetyl CoA

An intermediate formed in the link reaction by the joining of coenzyme A (CoA) and a two-carbon compound. This then enters the Krebs cycle.


A neurotransmitter in the central and peripheral nervous system. Drugs to increase acetylcholine are sometimes used to treat Alzheimer’s disease.


The dissolving of carbon dioxide in the oceans, which forms carbonic acid, lowering pH.


One of the main proteins involved in muscle contraction. Actin binds with myosin, and is then pulled by it to cause muscle to contract. Actin is also used in other situations to help move materials within the body.

Action potential

Describes the change in electrical potential in a membrane associated with the movement of an impulse along a neuron.

Active immunity

Immunity that occurs from the production of antibodies or T cells after exposure to an antigen – for example, following infection with a virus, or immunisation. This triggers the production of memory cells, which ensure a rapid immune response if the immune cells re-encounter a given antigen.

Active transport

The movement of molecules or ions across a membrane from a region of low concentration to a region of higher concentration (against a concentration gradient). This process requires energy, usually in the form of ATP, and assistance from an enzyme.


The practice of changing to accommodate and preparing for the consequences of a particular outcome. In the context of climate change, this could involve introducing more resilient crops or improving the design of infrastructure.

Adaptive immune system (also specific immune system)

In mammals, this provides long-lasting protection against specific foreign substances. Helper T cells stimulate plasma B cells to produce antibodies. Memory B cells maintain a ‘memory’ of previous infections the organism has fought.

Adenylyl cyclase (adenylate cyclase)

An enzyme that catalyses the formation of cyclic adenosine monophosphate (cAMP) from ATP.

Adherens junction

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


Cells specialised to store energy as fat, mainly as triglycerides. Also known as lipocytes or fat cells. Can be white, brown or beige.


Hormones produced by adipose tissue. They have a variety of effects on the body’s use of energy and storage. New ones are still being discovered.

ADP (adenosine diphosphate)

A molecule found in all living cells that is involved in the transfer of energy. It is produced when a phosphate group is removed from ATP, a process that releases energy.

Adrenoleukodystrophy (ALD)

An X-linked genetic disease characterised by the progressive deterioration of brain signalling and function.

Adverse reaction

A harmful side-effect of a medicine.


Using oxygen.


Having a pH greater than 7.


Different versions of the same gene.


Foreign proteins that can trigger a reaction from the immune system known as an allergy. An example is allergic rhinitis, also known as hay fever.

Amino acid

A compound that contains both an acidic group and an amino group. There are 20 biologically important amino acids that are present in proteins.

Aminoacyl tRNA synthetase

An enzyme that catalyses the binding of an amino acid to a tRNA molecule. There are at least 20 different types of this enzyme in the cell, each specific to a different amino acid.


A compound of one nitrogen atom and three hydrogen atoms (NH3). It occurs as a colourless gas and is thought to have been present in the atmosphere of the early Earth. Ammonia is created as a by-product of decay and decomposition and of animal waste.


AMP-activated protein kinase. An intracellular enzyme important in controlling the cell’s energy use. It is the key link between the body’s overall energy status and activity within the cell.


A small, almond-shaped structure within the brain involved in emotions, particularly fear.


A complex protein deposit that occurs in the liver, kidneys or other tissues in certain diseases.


The process by which large molecules are built up from smaller molecules. Anabolism is the opposite of catabolism and part of metabolism. Anabolic reactions require energy, which is frequently provided by ATP. Making skeletal muscle is an example of an anabolic reaction.


Without using oxygen.

Analogue sites

Places on Earth that have, or once had, similar biological, ecological or geological conditions to a body in outer space. These locations are the focus of intense research – informing how astrobiologists look for and identify life elsewhere in the universe.


Something that kills or inhibits the growth of microorganisms such as bacteria, fungi, parasites or viruses.


A substance that is produced by one microorganism and which inhibits or kills another. Antibiotics vary widely in structure. They can act either on a particular microorganism (ie they are specific) or a group of microorganisms (i.e. they are broad-spectrum).


A protein that is produced by plasma B cells to fight against antigens. All antibodies are immunoglobulins.


A group of three bases at one end of a tRNA molecule that is complementary to an mRNA codon.

Antigen-presenting cells (APCs)

Cells that break up invading particles or cells and then display parts of them – antigens – for other immune cells to inspect. APCs include the macrophages, dendritic cells and B cells.


Antigens are non-self markers, often proteins, that alert cells of the immune system to the presence of potential danger. These antigens may pose no threat on their own – they are just components, such as molecules in bacterial membranes, that raise a flag to immune cells.


Something that kills or inhibits the growth of microorganisms such as bacteria, fungi, parasites or viruses.


A molecule capable of absorbing free radicals (highly reactive molecules produced during many metabolic processes that can damage DNA). Whether eating foods high in antioxidants is beneficial to health is contentious.


Describes the side of the cell in relation to its position in the body; the apical membrane faces the outside surface of the body or the lumen of internal cavities.


The programmed and controlled cell death associated with ageing of the cell (reaching the Hayflick limit). This system often fails in cancer cells.


One of the three domains of life, archaea encompass any unicellular microorganisms that are genetically distinct from bacteria and eukarya, including organisms that inhabit extreme environments.


An inflammatory condition, causing pain, discomfort and stiffness in the joints.

Artificial immunity

Immunity induced by some kind of intervention, for example, vaccination.

Asexual reproduction

When an offspring is genetically identical to its (single) parent.


An investigative test to measure the activity or presence of a particular substance. For example, scientists might use an assay to calculate how quickly an enzyme breaks down a substrate.


The study of life in the universe, both on Earth and elsewhere. This branch of biology looks at the origin, evolution, distribution and future of life.


A condition in which fat within the arteries develops over years into fatty plaques. These plaques can eventually cause complete obstruction. Atherosclerosis mainly affects the aorta and the coronary and cerebral arteries. It can lead to cardiovascular disease.

ATP (adenosine triphosphate)

A molecule found in all living cells that is involved in the transfer of energy. Most of a cell’s ATP is made during respiration.

ATP synthase

An enzyme that catalyses the synthesis of ATP from ADP and inorganic phosphate (Pi), which occurs both in oxidative phosphorylation and during photosynthesis.


The wasting away of tissue, often due to inactivity or disease.


When the immune system fails to recognise self from non-self. Autoimmune diseases include rheumatoid arthritis, type 1 diabetes and Crohn’s disease.

Autonomic nervous system

The part of the nervous system that controls involuntary bodily functions, such as breathing, heartbeat and digestion. It is part of the peripheral nervous system.


A group of plant growth factors/hormones that: enable plants to respond to light, gravity and water; cause them to keep their leaves; and prioritise stem tip growth over side shoot growth. Includes indole acetic acid (IAA).


The long projection that carries signals away from the nerve cell body towards other neurons. The membrane voltage change from an incoming signal here triggers the opening of channels that allow ions (charged atoms) to flow into the cell from outside. This causes more channels further along the axon to open, creating an electrical signal (action potential) that propagates along it.