Biology Key Words

aminoacylase

enzyme used to produce pure samples of L-amino acids.

abscission

the fall of leaves.

acetyl coenzyme A

molecule that enters the Krebs cycle from glycolysis through a linking reaction when coenzyme A combines with an acetyl group.

acetylation

addition of acetyl group. increases transcription

action potential

the change in the potential difference across the neurone membrane of the axon when stimulated (approximately +40 mV).

active transport

movement of particles across a plasma membrane against a concentration gradient. Energy is required.

adenosine diphosphate (ADP)

a nucleotide composed of a nitrogenous base (adenine), a pentose sugar and two phosphate groups. Formed by the hydrolysis of ATP, releasing a phosphate ion and energy.

adenosine triphosphate (ATP)

a nucleotide composed of a nitrogenous base (adenine), a pentose sugar and three phosphate groups. The universal energy currency for cells.

alcoholic fermentation

fermentation that results in the production of ethanol.

alkaloids

bitter-tasting compounds found in plant leaves that may affect the metabolism of animals or insects eating them or poison them.

alleles

different versions of the same gene.

allopatric speciation

speciation that occurs as a result of a physical barrier between populations.

amino acids

monomer used to build polypeptides and thus proteins.

ammonification

conversion of nitrogen compounds in dead organic matter or waste into ammonium compounds by decomposers.

anabolic steroids

steroid drugs used illegally by some athletes and bodybuilders to increase muscle mass.

anaerobic respiration

respiration in the absence of oxygen.

antibodies

y-shaped glycoproteins made by B cells of the immune system in response to the presence of an antigen.

antidiuretic hormone (ADH)

hormone that increases the permeability of the distal convoluted tubule and the collecting duct to water.

antigen

identifying chemical on the surface of a cell that triggers an immune response.

apical dominance

the growth and dominance of the main shoot as a result of the suppression of lateral shoots by auxin.

apoptosis

programmed and controlled cell death important in controlling the body form and in the removal of damaged or diseased cells.

artificial selection

see selective breeding.

artificial twinning

the process of producing monozygotic twins artificially.

aseptic techniques

techniques used to culture microorganisms in sterile conditions so they are not contaminated with unwanted microorganisms.

autoimmune response

response when the immune system acts against its own cells and destroys healthy tissue in the body.

autonomic nervous system

part of the nervous system that is under subconscious control.

autosomal linkage

genes present on the same, non-sex chromosome.

auxins

plant hormones that control cell elongation, prevent leaf fall, maintain apical dominance, produce tropic responses, and stimulate the use of ethene in fruit ripening.

B effector cells

B lymphocytes that divide to form plasma cell clones.

B lymphocytes (B cells)

lymphocytes which mature in the bone marrow and that are involved in the production of antibodies.

B memory cells

B lymphocytes that live a long time and provide immunological memory of the antibody needed against a specific antigen.

baroreceptors

receptors which detect changes in pressure.

batch fermentation

an industrial fermentation that runs for a set time.

biodiversity

the variety of living organisms present in an area.

bioinformatics

the development of the software and computing tools needed to analyse and organise raw biological data.

biomass

mass of living material.

bioremediation

the use of microorganisms to break down pollutants and contaminants in the soil or water.

biotic factors

the living components of an ecosystem.

Bowman’s capsule

cup-shaped structure that contains the glomerulus and is the site of ultrafiltration in the kidney.

Calvin cycle

the cyclical light independent reactions of photosynthesis.

carbohydrates

organic polymers composed of the elements carbon, hydrogen and oxygen, usually in the ratio Cx(H2O)y.

carrier

a person who has one copy of a recessive allele coding for a genetically inherited condition.

carrying capacity

the maximum population size that an environment can support.

cell cycle

the highly ordered sequence of events that takes place in a cell, resulting in division of the nucleus and the formation of two genetically identical daughter cells.

cell wall

a strong but flexible layer that surrounds some cell-types.

central nervous system (CNS)

consists of the brain and spinal cord.

chemiosmosis

the synthesis of ATP driven by a flow of protons across a membrane.

chemoreceptors

receptors which detect chemical changes.

chi-square formula

formula used to determine the significance of the difference between observed and expected results.

chlorophyll

green pigment that captures light in photosynthesis.

chloroplasts

organelles that are responsible for photosynthesis in plant cells. Contain chlorophyll pigments, which are the site of the light reactions of photosynthesis.

chromatids

two identical copies of DNA (a chromosome) held together at a centromere.

chromatin

uncondensed DNA in a complex with histones.

chromosomes

structures of condensed and coiled DNA in the form of chromatin.

citrate

six carbon molecule formed in Krebs cycle by the combination of oxaloacetate and acetyl coenzyme A.

climax community

final stage in succession, where the community is said to be in a stable state.

clones

the offspring produced as a result of cloning.

cloning

a way of producing offspring by asexual reproduction.

codominance

when different alleles of a gene are equally dominant and both are expressed in the phenotype.

codon

a three-base sequence of DNA or RNA that codes for an amino acid.

coenzyme A

coenzyme with important roles in the oxidation of pyruvate in Krebs cycle and in the synthesis and oxidation of fatty acids.

collecting duct

final part of the tubule that passes through the renal medulla and the place where hypertonic urine is produced if needed.

communicable diseases

diseases that can be passed from one organism to another, of the same or different species.

competitive inhibitor

an inhibitor that competes with substrate to bind to active site on an enzyme.

complementary base pairing

specific hydrogen bonding between nucleic acid bases.

computational biology

the study of biology using computational techniques to analyse large amounts of data.

conservation

the maintenance of biodiversity.

consumer

organism that obtains its energy by feeding on another organism.

continuous fermentation

an industrial fermentation where culture broth is removed continuously and more nutrient medium added.

continuous variation

a characteristic that can take any value within a range, e.g. height.

correlation coefficient

statistical test used to consider the relationship between two sets of data.

cortex

the dark outer layer of the kidney containing the Bowman’s capsules and glomeruli.

cristae

fold of inner mitochondrial membranes, increases the surface area where reactions of the electron transfer chain can take place.

culture

growing living matter in vitro, for example, microorganisms in specifically prepared nutrient medium.

cyclic AMP

cyclic adenosine monophosphate, a molecule that acts as an important second messenger in many biological systems.

cyclic photophosphorylation

synthesis of ATP involving only photosystem I.

cytolysis

the bursting of an animal cell caused by increasing hydrostatic pressure as water enters by osmosis.

cytoplasm

internal fluid of cells, composed of cytosol (water, salts and organic molecules), organelles and cytoskeleton.

cytoskeleton

a network of fibres in the cytoplasm of a eukaryotic cell.

deamination

the removal of the amino group from amino acids.

decarboxylation

removal of carbon dioxide.

deciduous plants

plants that lose all of their leaves for part of the year.

decomposer

organism that breaks down dead organisms releasing nutrients back into the ecosystem.

decomposition

chemical reaction in which a compound is broken down into simpler compounds or into its constituent elements.

dehydrogenation

the removal of a hydrogen atom.

deletion

a mutation where one or more nucleotides are deleted and lost from the DNA strand.

denatured (denaturation)

change in tertiary structure of a protein or enzyme, resulting in loss of normal function.

denitrification

conversion of nitrates to nitrogen gas.

deoxyribonucleic acid (DNA)

the molecule responsible for the storage of genetic information.

depolarisation

a change in potential difference from negative to positive across the membrane of a neurone.

detoxification

removal or breakdown of toxins.

detritivore

organism which speeds up decay by breaking down detritus into smaller pieces.

diabetes mellitus

medical condition which affects a person’s ability to control their blood glucose concentration.

digenic inheritance

a characteristic controlled by two genes.

dihybrid inheritance

a characteristic inherited on two genes.

diploid

normal chromosome number; two chromosomes of each type − one inherited from each parent.

directional selection

natural selection that favours one extreme phenotype.

discontinuous variation

a characteristic that can only result in certain discrete values, for example, blood type.

disruptive selection

natural selection that favours both extremes of a given phenotype.

distal convoluted tubule

the second twisted section of the nephron where the permeability of the walls varies in response to ADH levels in the blood.