Biology- key terms & definitions

non-living factor e.g temperature, pH...
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A neurotransmitter released by neurones & passes an impulse from one neurone to next.
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Action potential
change to electrical charge across membrane of an axon when it is stimulated & a nerve impulse passes
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filamentous protein involved in contraction within cells
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Activation energy
minimum amount of energy required to bring about a reaction- lowered by presence of enzymes
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Active immunity
activities from an individual's own immune system- antigen induces plasma cells to produce antibodies
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Active site
group of amino's that make up region of enzyme into which substrate fits in order to catalyse reaction
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Active transport
Movement of substance against a concentration gradient, and requires expenditure of metabolic energy
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ATP/ Adenosine triphosphate
activated nucleotide found in all living cells & acts as an energy carrier- hydrolysis leads to ADP + Pi + energy
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hormone produced by adrenal glands in times of stress to prep body for emergency
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With the presence of oxygen- aerobic respiration= requires oxygen to release energy from glucose
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One of a number of alternative forms of a gene
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Allele frequency
number of times an allele occurs within a gene pool
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harmless substance that causes immune response from immune system
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response of immune system to an allergen
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Absence of oxygen- anaerobic respiration releases energy from glucose without oxygen
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substance produced by living organisms that can destroy/inhibit growth of micro-organisms
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Antibiotic resistance
development in micro-organisms of mechanisms that prevent antibiotics from killing them
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Protein produced by lymphocytes in response to presence of specific antigen
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sequence of 3 adjacent nucleotides on tRNA that is complimentary to codon on mRNA
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Hormone that reduces vol. of water in urine by increasing water reabsorption in the kidneys (secreted by hypothalmus --> posterior pituitary gland)
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molecule that triggers an immune response by lymphocytes
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Chemical which reduces or prevents oxidation- often used as an additive to prolong shelf-life of foods
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Apoplastic pathway
route through cell walls of plants by which water & dissolved substances are transported
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Artificial selection
breeding of organisms by human selection of parents/gametes in order to perpetuate certain characteristics and/or to eliminate others
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= restistance to air flow to alveoli= airways become inflamed due to an allergic response to allergen
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Fatty deposits in walls of arteries often associated w/ high cholesterol in blood
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Autonomic nervous system
part of nervous system controlling muscles & glands- not under voluntary control
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Chromosome which is not a sex chromosome
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process extending away from neurone, conducting A.P away from cell body
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white blood cell that matures in bone marrow as produces antibodies in their role in immunity
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Benedict's test
simple biochemical reaction to detect reducing sugars
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range & variety of genes, species & habitats in a particular region
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Total mass of living material, normally measured in a specific area over a given period of time
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living factors e.g competition, predation...
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device that uses biological molecules to measure level of certain chemicals
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Biuret test
biochemical reaction to test for presence of protein
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BMI/ Body Mass Index
body mass in kg divided by their heigh in metres squared
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Calvin cycle
Biochemical pathway that forms light-independent reaction of photosynthesis
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disease from cells that break away from an original tumour to form secondary tumours elsewhere in body
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A chemical, form of radiation, or other cancer causing agent
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Cardiac cycle
continuous series of events which make up a single heart beat
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Cardiac muscle
Type of muscle found in heart- fewer striations than skeletal muscle & can contract continously thoughout life without nervous stimulation
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Cardiac output
total volume of blood the heart can pump each minute
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Carrier protein/molecule
protein on surface of cell that helps to transpot molecules & ions across plasma membranes
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Casparian *****
distinctive band of suberin around enodermal cells of a plant root= prevent water passing into xylem via cell walls
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process of separating out particles of different sizes and densities by spinning them at high speed in centrifuge
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enzyme that breaks down & inactivates acetylcholine
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lipid= important component of cell-surface membranes
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One of 2 strands of a chromosome joined together by a centromere
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material that makes up chromosomes- consists of DNA & histones
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structure made of protein & DNA by which hereditary info passed down through generations
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Climax community
organisms that make up final stage of ecological succession
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group of genetically identical cells/ organisms formed from single parents as a result of asexual reproduction
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Both alleles for one gene are expressed
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sequence of 3 adjacent molecules in mRNA that code for one amino acid
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attraction between molecules of same type e.g water
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Fibrous protein that is main component of connective tissues e.g cartilage
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all living organisms present in an ecosystem at a given time
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Complementary DNA
DNA that is made from mRNA in a process that is the reverse of normal transcription
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combination of 2 molecules to form 1 complex and release of water
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method of maintaining ecosystems & the living organisms that occupy them
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any organisms that obtains energy by eating another
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Continuous variation
variation in which organisms do not fall into distincy categories but show gradations from one extreme to other
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Coronary arteries
arteries that supply blood to cardiac muscle
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Coronary heart disease
any condition affecting the coronary arteries that supply cardiac muscle
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when a change in 1 variable is reflected by a change in another variable
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transport of one substance coupled with transport of another substance across a plasms membrane in same direction through same protein carrier
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Countercurrent system
flow in opposite directions= increasing efficiency of exchange between 2 substances
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Covalent bond
2 atoms share a pair of electrons
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Crossing over
Chromatid breaks during meiosis and rejoins to chromatid of its homologous chromosome so that their alleles are exchanged
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exposed non-cellular outer layer of certain animals & leaves of plants
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term for plants that shed all their leaves together at one season
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permanent changes due to unravelling of 3D structure of a protein
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branched structure extending from cell body of a neurone which conducts impulses towards the cell body
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Denitrifying bactera
bacteria that converts nirtates to nitrogen gas as part of N cycle
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temporary reversal of charges on cell-surface membrane of neurone= takes place when a nerve impulse is transmitted
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body unable to regulate level of blood glucose
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stage in cardiac cycle where cardiac muscle relaxes
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process by which cells become specialised for specific functions
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movement of molecules/ions down a concentration gradient
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nucleus contains 2 sets of chromosomes
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having a pair of equal and opposite electrical charges
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Directional selection
selection that operates towards one extreme in a range of variation
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Discontinuous variation
Variation shown when characteristics of organisms fall into distinct categories
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DNA helicase
enzyme that acts on specific of DNA molecule to break H-bonds between bases causing strands to separate and expose nucleotide bases in that region
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DNA replication
double helix of DNA uwinds and each strand acts as a template on which a new strand is constructed
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Dominant allele
term applied to an allele that is always expressed in phenotype or organism
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Ecological niche
describes how an oganism fits into its environment, what a species is like, where it occurs, how it behaves & its interactions with other species and its environment
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all biotic & abiotic components of a particular area
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animal that uses environment to regulate its body temp
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organ that responds to stimulation by a nerve impulse resulting in change/response
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negatively charged subatomic particle that orbits protons and neutrons in nucleus
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Electron carrier molecule
chain of carrier molecules along which electrons pass, releasing energy in form of ATP as they do
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disease= walls of alveoli break down, reducing SA fpr gas exchange= breathlessness
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inward transport of large molecules through cell-surface membrane
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animal maintaining its body temp. by physiological mechanisms
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protein/RNA that acts as a catalyst & alters speed of biochemical reactions
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study of spread of disease & factors affecting the spread
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Eukaryotic cell
cell that has membrane-bound nucleus & chromosomes (animal & plant cells)
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Outward bulk transport of materials through cell-surface membrane
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Facilitated diffusion
involves protein carrier molecules to allow passive movement of substance across plasma membranes
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reproductive cell that fuses with another gamete in fertilisation
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Gel electrophoresis
technique used to separate DNA fragments of different lengths by placing them on agar gel & passing a voltage across them
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section of DNA on a chromosome coding for one or more polypeptides
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Gene pool
total no. of alleles in a partcular population at a specific time
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Gene marker
section of DNA that is used to indicate the location of a gene or other section of DNA
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Gene mutation
change to one or more nucleotide bases in DNA resulting in change in genotype which may be inherited
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Gene therapy
mechanism by which genetic diseases may be cured by masking the effect of the detective gene by inserting a functional gene
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Generator potential
depolarisation of membrane of a receptor cell as a result of stimulation
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Geneticically modified organisms
organisms that has had its DNA altered as a result of recombinant DNA tech
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The genetic composition of an organism
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Cluster of blood capillaries enclosed by Bowman's capsule in the kidney
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hormone produced by alpha cells that increase blood glucose levels
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conversion of non-carbohydrate molecules to glucose
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Conversion of glucose to glycogen
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the conversion of glycogen to glucose
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first part of cellular respiration in which glucose is broken down anaerobically in cytoplasm to give two molecules of pyruvate
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substance made up of carboydhrate molecule and a protein molecule- and makes up parts of cell surface membrane and certain hormones
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stack of thylakoids in a chloroplast, site of light-dependent stage of photosynthesis
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Guard cell
one of a pair of cells that surround a stoma in plant leaves and control its opening and closing
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place where an organism normally lives & which is characterised by physical conditions and the types of other organisms present
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globular protein in blood that combins with oxygen to transport it around the body
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cells that contain only a single copy of each chromosome (gametes)
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condition in which alleles of a gene are different
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proteins which DNA wind around to make up chromosomes
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maintenance of constant internal environment
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Homologous chromosomes
pair of chromosomes, one maternal & one paternal, that have the same gene loci and determine the same features but not identical as alleles of the same gene vary
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condition in which the alleles of a particular gene are identical
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Human genome
totality of the DNA sequences on the chromosomes of a single human cell
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Human genome project
international scientific project to map entire sequence of all the base pairs of the genes in a single human cell
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Hydrogen bond
chemical bond between positive charge on H and negative charge on N,O,F
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breaking down of large molecules into smaller ones by the addition of water
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conditions that results from the core body temperature rising above normal
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region of brain adjoining pituitary gland that acts as control centre for the autonomic nervous system and regulates body temp & fluid balance
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condition resulting in core body temperature falling below normal
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means by which body protects itself from infection
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hormone, produced by alpha cells which decreases blood glucose levels by increasing rate of conversion of glucose to glycogen
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practise of growing 2+ crops in close proximity to produce a greater yield on a piece of land
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Interspecific competition
competition between organisms of different species
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Interspecific variation
differences between organisms of different species
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Intraspecific competition
competition between organisms of the same species
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Intraspecific variation
differences between organisms of the same species
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Intrinsic proteins
proteins of the cell-surface membrane that completely span the phospholipid bilayer from one side to another
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portions of DNA within a gene that do not code for a polypeptide
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an atom or group of atoms that have lost/gained electrons giving them a positive or negative charge
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Ion channel
passage across cell-surface membrane made up of a protein that spans the membrane and opens and closes to allow ions to pass in and out of the cell
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Islets of Langerhans
groups of cells in the pancreas comprising large alpha cells, which produce glucagon and beta cells which produce insulin
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variations of a chemical element that have same numbr of protons but different number of neutrons
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In vitro
experiments carried out outside the living body
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In vivo
experiments that are carried out within living bodies
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Krebs cycle
series of aerobic biochemical reactions in matrix of mitochondria of most eukaryotic cells by which energy is obtained through the oxidation of acetyl-coA produced from breakdown of glucose
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Latent heat of vaporisation
heat taken in by a liquid in order to transform it into a vapour
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tough, fibrous, connective tissue, rich in collagen that joins bone to bone
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Light-dependent reaction
stage of photosynthesis in which light energy required to prduce ATP and reduced NADP
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Light-independent reaction
stage of photosynthesis which doesn't require light energy directly but does need products of light-dependent reaction to reduced CO2 and so form carbohydrate
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Limiting factor
variable that limits the rate of a chemical reaction
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Link reaction
process linking glycolysis with krebs cycle
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position of a gene on a chromosome/DNA molecule
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Loop of Henle
portion of the nephron that forms the hairpin loop that extends into the medulla of the kidney
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hollow cavity inside a tubular structure
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Slightly milky fluid found in lymph vessels & made up of tissue fluid, fats and lymphocytes
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types of white blood cell responsible for the immune response
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type of nuclear division in which number of chromosomes is halved
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tissue found between 2 layers of epidermis in a plant leaf and compromising an upper layer of palisade cells and a lower layer or spongy cells
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all the chemical processes that take palce in living organisms
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tiny finger-like projections from cell-surface membrane of some animal cells
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Middle lamella
layer made up of pectins and other substances found between the walls of adjacent plant cells
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nuclear division that leads to daughter cells with the same number of chromosomes as the parent cell
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Monoclonal antibodies
antibody produced by a single clone of cells
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one of many small molecules that combine to form one larger molecule- a polymer
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Mono-unsaturated fatty acid
fatty acid that possesses a carbon chain with a single double bond
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Motor neurone
neurone that transmits action potentials from C.N.S to an effector
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Multiple alleles
term used to describe a gene that has more than two possible alleles
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any agent that induces a mutation
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sudden change in amount or arrangement of genetic material in the cell
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nutritional relationship between two species in which both gain some advantage
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fatty substance that surrounds axons and dendrites in certain neurones
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Myocardial infarction
heart attack, resulting from interruption of blood supply to heart muscle causing damage to an area of the heart & its function
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thick filamentous protein found in skeletal muscle
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molecule that carries electrons and hydrogen ions during aerobic respiration
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molecule that carries electrons produced in the light-dependent reaction of photosynthesis
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Negative feedback
series of changes that result in substance being returned to its normal level- important in homeostasis
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basic functional unit of kidney responsible for urine formation
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nerve cell, compromising of cell body, axon and dendrites which is adapted to conduct action potentials
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Neuromuscular junction
Synapse that occurs between a neurone and a muscle
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One of many chemicals that are involved in communication between adjacent neurones/ nerve cells and muscle cells
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Nitrifying bacteria
Microorganisms that convert ammonium compounds to nitrites and nitrates
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Nitrogen fixation
Incorporation of atmospheric N into organic N-containing compounds
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Normal distribution
bell-shaped curve produced when distribution is plotted on graph
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Node of Ranvier
gap in myelin sheath that surrounds the axon of a neuron
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Organic base, sugar and a phosphate- the basic units of which DNA and RNA are made
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the period in the oestrous cycle immediately after ovulation when the female is most fertile
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mutated versions of proto-oncogenes that result in increased cell division leading to tumour growth
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Oral rehydration solution
means of treating dehydration involving giving a balanced solution of salts and glucose that stimulates gut to reabsorb water
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Net movement of water down a water potential gradient through a selectively permeable membrane
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Loss of electrons
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Electrons transferred from one substance to another
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Oxidative phosporylation
formation of ATP in the electron transport system of aerobic respiration
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Palisade cells
long, narrow cells packed with chloroplasts that are found in upper region of a leaf and carry out photosynthesis
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Organism that lives on or in a host organism- parasite gains a nutritional advantage and host is harmed in some way
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Passive immunity
resistance to disease that is acquired from introduction of antibodies from another individual, rather than an individual's own immune system
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microorganism that causes disease
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Pentose sugar
sugar that possesses give C atoms
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Peptide bond
Chemical bond between 2 amino acids during condensation
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mechanism where cells engulf particles to form a vesicle or vacuole
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the (usually) visible characteristics of an organism resulting from its genotype & the environment its in
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plant tissue that transports products of photosynthesis from leaves to rest of plant
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triglyceride in which 1/3 fatty acids replaced by phosphate- important in structure and function of plasma membranes
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splitting of water molecule by light
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Photograph of an image produced by a microscope
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Pioneer species
species that can colonise bare rock or ground
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small, circular piece of DNA found in bacterial cells
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fine strands of cytoplasm that extrend through pores in adjacent plant cell walls and connect cytoplasm of one cell with another
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skrinkage of cytoplasm away from cell wall that occurs as a plant cell loses water by osmosis
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group of genes that are responsible for controlling a characteristic
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large molecule made up of repeating monomer units
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Polymerase Chain Reaction/ PCR
Process of making many copies of a specific sequence of DNA or part of a gene- used extensively in gene tech and genetic fingerprinting
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Enzymes that catalyse formation of polymers from monomers
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Polyunsaturated fatty acid
fatty acid that possesses carbon chains with many double bonds
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group of individuals of same species that occupy the same habitat at the same time
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Positive feedback
Process which results in substance departing further from its normal level
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Primary protein structure
sequence of aminos that make up polypeptides of a protein
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Primary succession
the progressive colonisation of bare rock or barren terrain by living organisms
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organism that synthesises organic molecules from simple inorganic ones such as carbon dioxide and water- most are photosynthetic and from first trophic level of food chain
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Prokaryotic cell
cell of an ogranism characterised by lacking nucleus and membrane-bound organelles (bacteria)
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positively charged sub-atomic particle found in nucleus of an atom
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living portion of a plant cell- the nucleus, cytoplasm and the organelles it contains
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Quartnerary protein structure
number of polypeptide chains linked together and sometimes associated with non-protein groups to form a protein
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cell adapted to detect changes in an environment
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Recessive allele
condition in which effect of allel is apparent in the phenotype of a diploid organism only in the presence of an identical allele
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Recognition site
nucleotide sequence, usually of 4,6, or 8 nucleotides that is recognised by a restriction endonuclease and to which it attatches
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recombinant DNA technology
general term that covers processes by which genes are altered/transferred from one organism to another
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gain of electrons
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Reflex arc
nerve pathway in the body taken by an action potential that leads to rapid, involuntary response to a stimulus
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Refractory period
Period during which the membrane of the axon of a neurone cannot be depolarised= no new AP can be initiated
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Renal capsule
cup shaped portion of start of nephron that encloses the glomerulus
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return to the resting potential in the axon of a neurone after an action potential
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Resting potential
difference in electrical charge maintained across the membrane of the axon of a neurone when not stimulated
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Restriction endoucleases
group of enzymes that cut DNA molecules at a specific sequence of bases called a recognition sequence
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RNA polymerase
enzyme that joins together nucleotides to form mRNA during transcription
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Saltatory conduction
propagation of nerve impulse along a myelinated dendron/axon in which action potentials jump between nodes of Ranvier
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Saprobiotic microorganism
organisms that obtains its food from dead or decaying remains of other organisms
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section of myofibril between 2 Z-lines that form basic structural unit of skeletal muscle
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Saturated fatty acid
no double bonds between carbon atoms
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Schwann cell
cell around a neurone who cell-surface membrane wraps around the dendron/axon to form the myelinated sheath
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Secondary protein structure
way in which amino's of a polypeptide of a protein are folded
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Secondary succession
recolonisation of an area after an earlier community has been removed/destroyed
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process that results in best-adapted individuals in a population to survive and breed to pass on favourable alleles to next generation
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Selection pressure
environmental force altering the frequency of alleles in a population
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Selective breeding
breeding of organisms by human selection of gametes in order to create certain characteristics/eliminate others
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Semi-conservative replication
means by which DNA makes exact copies of itself by unwinding the double helix so that each chain acts as a template= new copies possess one original and one new strand of DNA
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Sensory neurone
neurone that transmits action potential from sensory receptor to central nervous system
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clear liquid left after blood has clotted and blood clot is removed /blood plasma without the clotting factors
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Sickle-cell anaemia
inherited blood disorder where abnormal haemoglobin leads to red blood cells becoming sickle-shaped and less able to carry oxygen
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Sinoatrial node
area of heart muscle that controls and coordinates contraction of the heart
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Skeletal muscle
muscle that makes up bulk of body and works under conscious control
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Smooth muscle
involuntary/unstriated muscle= found in walls of blood vessels
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Sodium-potassium pump
protein channels across cell-surface membranes that use ATP tomove sodium ions out of cell in exchange for potassium ions that move in
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evolution of two or more species from existing species
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group of similar organisms that can breed together to produce fertile offspring
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Species diversity
Number of different species and number of individuals of each species in a community
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Stabilising selection
Selection that tends to eliminate extremes of the phenotype range within a population- arises when environmental conditions are constant
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Stem cells
undifferentiated dividing cells that occur in embryos and in adult animal tissues that require constant replacement
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detectable alteration in the internal/external evironment of an organism that produces a change in that organism
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pore mostly found in lower epidermis of a leaf through which gases diffuse in and out of leaf
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Stroke volume
volume of blood pumped out at each ventricular contraction of the heart
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matrix of chloroplast where light-independent reaction of photosynthesis occurs
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substance that is acted on or used by another substance or process
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Sustrate-level phosphorylation
formation of ATP by direct transfer of a phosphate group from a reactive intermediate to ADP
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Supernatant liquid
the liquid portion of a mixture left at the top of the tube in ultracentrifugation
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Symplastic pathway
route through cytoplasms of plant cells by which water and dissolved substances are transported
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junction between neurones in which they dont touch but have synaptic cleft across which neurotransmitter can pass
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Stage in cardiac cycle in which heart muscle contracts
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tough, flexible, but inelastic, connective tissue that joins muscle to bone
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Tertiary protein structure
folding of whole polypeptide chain in precise way determined by amino acids its composed of
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Threshold level/value
minimum intensity that a stimulus must reach in order to trigger an action potential in a neurone
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formation of a blood clot within a blood vessel that may lead to a blockage
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series of flattened sacs in chloroplast that contain chlorophyll and the associated molecules needed for the light-dependent reaction
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Tidal volume
volume of air breathed in and out during a single breath when at rest
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group of similar cells organised into a structural unit that serves a particular function
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Tissue fluid
fluid that surrounds the cells of body- composition= similar to blood plasma but lacks proteins. It supplies nutrients to cell and removes waste products
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type of white blood cell produced in bone marrow but matures in thymus gland. T lymphocytes coordinate the immune response and kill infected cells
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Formation of mRNA molecules from DNA that makes up a particular gene
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Transducer cells
convert a non-electrical signal e.g light into anelectrical signal and vice versa
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process by wihch one form of energy is converted into another. In microbiology= natural process by which genetic material trasnferred between host cell to another by a virus
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evaporation of water from a plant
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lipid molecule: 3 fatty acids + a glycerol
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Trophic level
position of an organism in a food chain
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swelling in an organism made up of cells continually dividing in an abnormal way
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Tumour suppressor gene
gene that maintains normal rates of cell division & prevents devt. of tumours
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plant cell that contains max. vol of water it can- additional entry of water prevented by cell wall stopping further expansion of cell
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Filtration assisted by blood pressure e.g in formation of tissue fluid
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Unsaturated fatty acid
fatty acid in which there are one or more double bonds between carbon atoms
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introduction of vaccine containing appropriate disease antigens into body by njection/mouth to induce artifical immunity
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narrowing of internal diameter of blood vessels
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widening of internal diameter of blood vessels
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a carrier- e.g plasmids are vectors which carry DNA into a cell or to an organism that carries a parasite to its host
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Voltage-gated channels
protein channel across cell-surface membrane that opens and closes according to changes in electrical potential across membrane
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Water potential
pressure created by water molecules & is a measure of the extent to which a solution gives out water
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plant adapted to living in dry conditions
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Xylem vessels
dead, hollow, elonogated tubes, with lignified side walls & no end walls that transport water in plants
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Card 2


A neurotransmitter released by neurones & passes an impulse from one neurone to next.



Card 3


change to electrical charge across membrane of an axon when it is stimulated & a nerve impulse passes


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Card 4


filamentous protein involved in contraction within cells


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Card 5


minimum amount of energy required to bring about a reaction- lowered by presence of enzymes


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