A To Z Of Biology

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Abundance

Back 1

The frequency of occurrence of organisms in a sampled area, such as a quadrat.

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Activation Energy

Back 2

The level of energy required to enable a reaction to take place. Enzymes reduce the amount of energy required to allow a reaction to proceed.

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Active Immunity

Back 3

Immunity that is acquired by activation of immune system.

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Active Site

Back 4

The area on an enzymes molecule to which the substrate binds.

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Activate Transport

Back 5

Movement of substances across membranes against their concentration gradient requiring the use of energy in the form of ATP. Active transport usually involves the use of transport proteins.

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Adaptation

Back 6

A feature of a living organism that increases its chances of survival for example thick fur on an animal that lives in a cold habitat.

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Adenine

Back 7

A nitrogen containing organic base found in nucleic acids. It pairs with Thymine in DNA and with Uracil in RNA.

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Adhesion

Back 8

Forces of attraction between molecules of two different substances.

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Adipose

Back 9

Describes tissue consisting of cells that store fat/lipid.

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Affinity

Back 10

An attraction force between substances of particles.

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Allele

Back 11

A version of a gene.

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Allopatic

Back 12

Speciation due to organism of a species being separated by geographical barriers so that over time members of the two population become so different that they cannot interbreed and are considered to be two different species.

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Alveoli

Back 13

Small air sacs in the lungs.

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Amino acid

Back 14

An organic compound that contains both an amino group (-NH2) and carboxyl group (-COOH). Amino acids are the monomers of protein molecules.

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Amylase

Back 15

An enzyme that catalyses the hydrolysis of starch to maltose.

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Amylose

Back 16

One form of starch consisting of a helical chain of thousands of glucose residues bonded together.

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Anaphase

Back 17

In mitosis the stage when the newly separated chromatids are pulled towards opposite poles of the nuclear spindle.

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Anomalous

Back 18

Describes a result/data point that does not appear to fit the pattern of the other results. It may be assumed to be anomalous if the experimenter has made a error or if the apparatus used is not suitable for the measurements being taken.

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Antibiotics

Back 19

Molecules produced by microorganisms that kill or limit the growth of other mircoorganisms.

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Antibodies

Back 20

Protein molecules released by the immune system in response to an antigen which are capable of neutralising the effects of the antigen.

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Antigens

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A foreign molecule (which may be protein or glycoprotein) that can provoke an immune response. Organisms have antigens on their plasma (cell surface) membranes.

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Antigen-presenting cell

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A macrophage that has ingested a pathogen and displays the pathogen's antigens on its cell surface membrane.

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Apoplast Pathway

Back 23

The route taken by water between the cells or through the cell walls in a plant.

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Arterioslerosis

Back 24

Hardening of the artery walls and loss of elasticity caused by atherosclerosis and deposition of calcium.

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Artificial immunity

Back 25

Immunity acquired as a result of deliberate exposure to antigens or by the injection of antibodies.

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Artificial Selection

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Also called selective breeding, the process of improving a variety of crop plant or domesticated animal by breeding from selected individuals with desired characteristics.

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Asexual Reproduction

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The production of genetically identical new organisms be a single 'parent' organism.

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Assay

Back 28

The use of comparative studies or samples to determine the concentration or quality of a substance in a sample.

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ATP

Back 29

Adenosine triphosphate

A molecule used as the 'energy currency' in organisms. The molecule is broken down to adenosine diphoshate + phosphate to release energy to drive metabolic processes.

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Atrioventricular Node (AVN)

Back 30

A patch of tissue in the septum of the heart that conducts the electrical stimulus from the atria in the heart through to the Purkyne fibres.

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Atrioventricular Valves

Back 31

Valves between the atria and the ventricles that prevent backflow of blood.

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Atrium

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One of the upper chambers in the heart.

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Autotroph

Back 33

An organism that makes its own food from simple inorganic molecules such as carbon dioxide and water. Some (Photoautotrophs) e.g plants use light as the source of energy. Some (Chemoautophs) e.g some bacteria use chemical energy