AQA Glossary Flashcards
Learn all the key definitions
Definition
Key word
An ecological factor that makes up part of the non-biological environment of an organism
Abiotic
One of a group of chemicals called neurotransmitters released by neurones. It diffuses across the synapse between adjacent neurones and so passes an impulse from one neurone to another
Acetylcholine
Change that occurs in the electrical charge across the membrane of an axon when it is stimulated and a nerve impulse passes
Action potential
Filamentous protein which is involved in contraction within cells, especially muscle cells
Actin
Energy required to bring about a reaction. The _______ ________is lowered by the presence of enzymes
Activation energy
Resistance to disease resulting from the activities of an individual’s own immune system whereby an antigen induces plasma cells to produce antibodies
Active immunity
A group of amino acids that makes up the region of an enzyme into which the substrate fits in order to catalyse a reaction
Active site
Movement of a substance from a region where it is in a low concentration to a region where it is in a high concentration. The process requires the expenditure of metabolic energy
Active transport
A hormone produced by the adrenal glands in times of stress that prepared the body for an emergency
Adrenaline
Connective with the presence of free oxygen. Aerobic respiration requires free oxygen to release energy from glucose
Aerobic
One form of a gene
Allele
The number of times an allele occurs within the gene pool
Allele frequency
A normally harmless substance that causes the immune system to produce an immune response
Allergen
The response of the immune system to an allergen. E.g. hay fever
Allergy
Connected with the absence of oxygen. Anaerobic respiration releases energy from glucose or other foods without the presence of oxygen
Anaerobic
A substance produced by a living organism that can destroy or inhibit the growth of microorganisms
Antibiotic
The development in microorganisms of mechanisms that prevent antibiotics from killing them
Antibiotic resistance
A protein produced by lymphocytes in response to the presence of the appropriate antigen
Antibody
A sequence of three adjacent nucleotides on a molecule of transfer RNA that is complementary to a particular codon on a messenger RNA molecule
Anticodon
A molecule that triggers an immune response by lymphocytes
Antigen
A chemical which reduces or prevents oxidation. Often used as an additive to prolong the shelf-life of certain foods
Antioxidant
Route through the cell walls and intercellular spaces of plants by which water and dissolved substances are transported
Apoplastic pathway
Breeding of organisms by human selection of parents/gametes in order to perpetuate certain characteristics and/or eliminate others
Artificial selection
A chronic illness in which there is resistance to air flow to the alveoli of the lungs as a result of the airways becoming inflames due to an allergic response to an allergen
Asthma
Fatty deposits in the walls of arteries, often associated with high cholesterol levels in the blood
Atheroma
Nucleotide found in all living organisms, which is produced during respiration and is important in the transfer of energy
ATP (adenosine triphosphate)
Part of the nervous system, controlling the muscles and glands that are not under voluntary control
Autonomic nervous system
A process extending from a neurone that conductions action potentials away from the cell body
Axon
A type of white blood cell that is produced and matures within the bone marrow. They produce antibodies as part of their role in immunity
B cell ((B lymphocyte)
A simple biochemical reaction to detect the presence of reducing sugars
Benedict’s test
The range and variety of genes, species and habitats within a particular region
Biodiversity
The total mass of living material, normally measured in a specific area over a given period of time
Biomass
A simple biochemical reaction to detect the presence of protein
Biuret test
A person’s body mass in kilograms divided by the square of their height in metres
Body mass index (BMI)
A biochemical pathway that forms part of the light-independent reaction of photosynthesis, during which carbon dioxide is reduced to form carbohydrate
Calvin cycle
A disease, resulting from mutations, that leads to uncontrolled cell division and the eventual formation of a group of abnormal cells called a tumour
Cancer
A chemical, form of radiation or other agent that causes cancer
Carcinogen
A (continuous series of events which make up a single heartbeat
Cardiac cycle
A type of muscle found only in the heart, can contract continuously throughout life without stimulation by nerve impulses
Cardiac muscle
The total volume of blood that the heart can pump in each minute (stroke volume X heart rate)
Cardiac output
A protein on the surface of a cell that helps to transport molecules and ions across plasma membrane
Carrier molecule (carrier protein)
A distinctive band of suberin around the endodermal cells of a plant root that prevents water passing into xylem via the cell walls
Casparian strip
Process of separating out particles of different sizes and densities by spinning them at a high speed in a centrifuge
Centrifugation
Lipid that is an important component of cell-surface membranes
Cholesterol
An enzyme that breaks down and therefore inactivates the neurotransmitter acetylcholine in the synapse
Cholinesterase
One of the two copies of a chromosome that are joined together by a single centromere prior to cell division
Chromatid
A thread-like structure made of protein and DNA by which hereditary information is physically passed from one generation to the next
Chromosome
The organisms that make up the final stage of ecological succession
Climax community
A group of genetically identical organisms formed from a single parent as a result of asexual reproduction or by artificial means
Clone
Condition in which both alleles for one gene in a heterozygous organism contribute to the phenotype
Co-dominance
A sequence of three adjacent nucleotides in mRNA that codes for one amino acid
Codon
Attraction between molecules of the same type. It is important in the movement of water up a plant
Cohesion
Fibrous protein that is the main constituent of connective tissues
Collagen
All the living organisms present in an ecosystem at a given time
Community
DNA that is made from messenger RNA in a process that is the reverse of normal transcription
Complementary DNA
A chemical process in which two molecules combine to form a more complex one with the elimination of a simple substance, usually water
Condensation
The transfer of DNA from one cell to another by means of a thin tube between the two
Conjugation
Method of maintaining ecosystems and the living organisms that occupy them
Conservation
Variation in which organisms do not fall into distinct categories but show gradations from one extreme to the other
Continuous variation
Arteries that supply blood to the cardiac muscle of the heart
Coronary arteries
Any condition affecting the coronary arteries that supply heart muscle
Coronary heart disease (CHD)
When a change in one variable is reflected by a change in the second variable
Correlation
A mechanism by which the efficiency of exchange between two substances in increased by having them flowing in opposite directions
Countercurrent system
A type of chemical bond in which two atoms share a pair of electrons, one from each atom
Covalent bond
The process whereby a chromatid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are exchanged
Crossing over
Exposed non-cellular outer layer of certain animals and the leaves of plants
Cuticle
Inherited disease in which the body produces abnormally thick mucus that obstructs breathing passages and prevents secretion of pancreatic enzymes
Cystic fibrosis
Term applied to plants that shed all their leaves together at one season
Deciduous
Permanent changes due to the unravelling of the three-dimensional structure of a protein as a result of factors such as changes in temperature
Denaturation
A process, usually branched, extending from the cell body of a neurone which conducts impulses towards the cell body
Dendrite
Bacteria that converts nitrates to nitrogen gas as part of the nitrogen cycle
Denitrifying bacteria
Temporary reversal of charges on the cell-surface membrane of a neurone that takes place when a nerve impulse is transmitted
Depolarisation
A metabolic disorder in which the body is unable to regulate the level of blood glucose
Diabetes
The stage in the cardiac cycle when the heart muscle relaxes
Diastole
Any member of the class of flowering plants called Dicotyledonae
Dicotyledonous plants
The process by which cells become specialised for different functions
Differentiation
The movement of molecules or ions form a region where there are in high concentration to one where their concentration is lower
Diffusion
Cells in which the nucleus contains two sets of chromosomes
Diploid
Variation shown when the characteristics of organisms fall into distinct categories
Discontinuous variation
An enzyme that acts on a specific region of the DNA molecule to break the hydrogen bonds between the bases causing the two strands to separate and expose the nucleotide bases in that region
DNA helicase
The process in which the double helix of a DNA molecule unwinds and each strand acts as a template on which a new strand is constructed
DNA replication
An allele that is always expressed in the phenotype of an organism
Dominant allele
All conditions and resources required for an organism to survive, reproduce and maintain a viable population
Ecological niche
More of less self-contained functional unit in ecology made up of all the interacting biotic and abiotic factors in a specific area
Ecosystem
An animal that uses the environment to regulate its body temperature
Ectothermic
An organ that responds to stimulation by a nerve impulse resulting in a change or response
Effector
Negatively charged sub-atomic particle that orbits the positively charged nucleus of all atoms
Electron
A chain of carrier molecules along which electrons pass, released energy in the form of ATP as they do so
Electron carrier molecule
A disease in which the walls of the alveoli break down, reducing the surface area for gaseous exchange, thereby causing breathlessness
Emphysema
An animal maintaining its body temperature by physiological mechanisms
Endotherm
A protein or RNA that acts as a catalyst and so alters the speed of a biochemical reaction
Enzyme
The study of the spread of disease and the factors that affect this spread
Epidemiology
A cell that has a membrane-bound nucleus and chromosomes
Eukaryotic cell
Consequence of an increase in nutrients, especially in nitrates and phosphates, in fresh water lakes and rivers, that often leads to a decrease in biodiversity
Eutrophication
Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across plasma membranes
Facilitated diffusion
Reproductive cell that fuses with another gamete during fertilisation
Gamete
A technique used to separate DNA fragments of different lengths by placing them on an agar gel and passing a voltage across them
Gel electrophoresis
A section of DNA on a chromosome coding for one or more polypeptide
Gene
The total number of alleles in a particular population at a specific time
Gene pool
A section of DNA that is used to indicate the location of a gene or other section of DNA
Gene marker
A mechanism by which genetic diseases may be cured by masking the effect of the defective gene by inserting a functional gene
Gene therapy
Depolarisation of the membrane of a receptor cell as a result of a stimulus
Generator potential
Organism that has had its DNA altered as a result of recombinant DNA technology
Genetically modified organism (GMO)
The genetic composition of an organism
Genotype
A hormone produced by α cells at the islets of Langerhans in the pancreas that increases blood glucose levels by initiating the breakdown of glycogen to glucose
Glucagon
The conversion of non-carbohydrate molecules into glucose
Gluconeogenesis
The conversion of glucose to glycogen
Glycogenesis
First part of cellular respiration in which glucose is broken down anaerobically in the cytoplasm to two molecules of pyruvate
Glyconeolysis
Substance made up of a carbohydrate molecule and a protein molecule
Glycoprotein
A stack of thylakoids in a chloroplast that resembles a pile of coins, this is the site of the light-dependent reaction of photosynthesis
Granum
Gases such as methane and carbon dioxide which in the atmosphere cause more heat energy to be trapped, so raising the temperature at the Earth’s surface
Greenhouse gas
One of a pair of cells that surround a stoma in plant leaves and controls its opening and closing
Guard cell
The place where an organism normally lives which is characterised by physical conditions and the types of other organisms present
Habitat
Globular protein in blood that readily combines with oxygen to transport it around the body
Haemoglobin
Cells that only contain a single copy of each chromosome
Haploid
Condition in which the alleles of a particular gene are different
Heterozygous
