A
- Active site
- Region of an enzyme where the substrate binds and the reaction takes place.
- Allele
- One version of a gene. Different alleles of a gene can give different forms of the same characteristic. See also: Gene, Genotype.
- Antibiotic
- A medicine that kills or stops the growth of bacteria. It has no effect on viruses.
- Antibody
- A protein made by white blood cells that binds to a specific antigen on a pathogen. See also: Antigen.
- Antigen
- A molecule on the surface of a cell or pathogen that the immune system can recognise as foreign. See also: Antibody.
B
- Bile
- A liquid made in the liver and stored in the gall bladder. It neutralises stomach acid and breaks fat into droplets.
C
- Capillary
- A very small blood vessel with walls one cell thick, where substances are exchanged between blood and body cells.
- Carbohydrase
- An enzyme that breaks down carbohydrates into simple sugars. Amylase is an example.
- Chlorophyll
- Green pigment in chloroplasts that absorbs light energy for photosynthesis.
- Chromosome
- A long, coiled molecule of DNA carrying many genes, found in the nucleus of a cell.
- Clone
- An organism that is genetically identical to its parent, for example one produced by asexual reproduction.
D
- Denatured
- Describes an enzyme whose active site has changed shape, usually because of high temperature or extreme pH, so it can no longer work.
- Diffusion
- Net movement of particles from a region of higher concentration to a region of lower concentration. See also: Osmosis.
- DNA
- Molecule that carries genetic information in a double helix made of two strands.
- Dominant allele
- An allele that shows its characteristic when only one copy is present.
E
- Ecosystem
- All the living organisms in an area together with the non-living parts of their environment.
- Effector
- A muscle or gland that carries out a response after it receives a signal from the nervous system.
- Enzyme
- A biological catalyst, made of protein, that speeds up a reaction without being used up. See also: Active site, Denatured.
- Evolution
- Gradual change in the inherited characteristics of a population over many generations.
G
- Gamete
- A sex cell, such as a sperm cell or an egg cell, which has half the usual number of chromosomes.
- Gene
- A short section of DNA that codes for a particular protein. See also: Allele, Chromosome.
- Genotype
- Combination of alleles that an organism has for a characteristic.
- Glucose
- A simple sugar made in photosynthesis and used in respiration to release energy.
H
- Heterozygous
- Having two different alleles of a gene, for example Bb.
- Homeostasis
- Keeping conditions inside the body, such as temperature and blood glucose, within a narrow range. See also: Negative feedback.
- Homozygous
- Having two identical alleles of a gene, for example BB or bb.
- Hormone
- A chemical messenger made by a gland and carried in the blood to target organs.
I
- Insulin
- A hormone made by the pancreas that causes glucose to move from the blood into cells, lowering blood glucose. See also: Homeostasis, Negative feedback.
L
- Limiting factor
- A factor in short supply that stops the rate of a process, such as photosynthesis, from increasing.
M
- Meiosis
- Cell division that produces four genetically different gametes, each with half the normal number of chromosomes. See also: Mitosis, Gamete.
- Mitochondria
- Structures in cells where aerobic respiration releases most of the cell’s energy.
- Mitosis
- Cell division that produces two genetically identical daughter cells, used for growth and repair. See also: Meiosis.
- Mutation
- A change in the DNA sequence of a gene. Most have little or no effect on the protein, a few change it, and a mutation in a gamete can be inherited.
N
- Natural selection
- Process by which organisms with characteristics suited to their environment are more likely to survive, reproduce and pass on their alleles. See also: Variation, Evolution.
- Negative feedback
- A control system in which a change is detected and a response reverses it, bringing the level back towards normal.
- Neurone
- A nerve cell that carries electrical impulses.
O
- Osmosis
- Movement of water across a partially permeable membrane from a dilute solution to a more concentrated solution. See also: Diffusion.
P
- Pathogen
- A microorganism that causes disease, such as a bacterium, virus, fungus or protist.
- Phenotype
- Observable characteristics of an organism, produced by its genotype and its environment.
- Photosynthesis
- Process in which plants use light energy to make glucose from carbon dioxide and water, releasing oxygen. See also: Respiration, Limiting factor.
R
- Receptor
- A cell or structure that detects a stimulus and converts it to a signal.
- Recessive allele
- An allele that only shows its characteristic when two copies are present.
- Reflex action
- A rapid, automatic response to a stimulus that does not involve conscious thought.
- Respiration
- Chemical process in all living cells that releases energy from glucose. See also: Photosynthesis, Mitochondria.
S
- Specialised cell
- A cell with a structure adapted to carry out a particular job.
- Stem cell
- An undifferentiated cell that can divide and develop into other types of cell.
- Stimulus
- A change in the surroundings that an organism can detect.
- Substrate
- Molecule that an enzyme acts on.
T
- Transpiration
- Loss of water vapour from plant leaves, mainly through stomata, which draws water up the plant.
V
- Variation
- Differences in characteristics between individuals of the same species.
X
- Xylem
- Plant tissue made of hollow tubes that carries water and mineral ions from the roots to the leaves.
See also
Wording and emphasis vary between exam boards, so check your own specification for the exact terms used.
Part of the GCSE Biology revision set: the revision guide and self-marking quiz.