biology key words

activation energy
energy required to bring about a reaction. the activation energy is lowered y the presence of enzymes.
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active immunity
resistance to disease resulting from the activities of an individual's own immune system whereby an antigen induces plasma cells.
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active site
a group of amino acids that make the region of an enzyme into which the substrate fits in order to catalyse a reaction
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active transport
movement of a substance from a region where it is in a high concentration. the process requires the expenditure of metabolic energy.
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connected with the presence of free oxygen. Aerobic respiration requires free oxygen to release energy from glucose.
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one of a number of alternative forms of a gene. for example, the gene for shape of pea seeds has two alleles: one for 'round' and one for 'wrinkled'
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a substance produced by living organisms that can destroy or inhibit the growth of microorganisms
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antibiotic resistance
the development in micro-organisms of mechanisms that prevent antibiotics from killing them
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a protein produced by lymphocytes in response to the presence of the appropriate antigen
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a molecule that triggers an immune response by lymphocytes
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process of separating out particles of different sizes and densities by spinning them at high speed in a centrifuge
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one of the two copies of a chromosome that are joined together by a single centromere prior to cell division
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a thread-like structure made of protein and DNA by which hereditary information is physically passed from one generation to the next.
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a group of genetically identical cells or organisms formed from a single parent as the result of asexual reproduction or by artificial means.
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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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attraction between molecules of the same type. It is important in the movement of water up a plant.
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chemical process in which two molecules combine to form a more complex one with the elimination of a simple substance, usually water. many biological polymers, such as polysaccharides and poly peptides, are formed by condensation.
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the transfer of DNA from one cell to another y means of a thin tube between the two.
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continuous variation
variation in which organisms do not fall into distinct categories but show gradations from one extreme to another
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crossing over
the process whereby a chromotid breaks during meiosis and rejoins to the chromatid of its homologous chromosome so that their alleles are exchanged.
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the stage in the cardiac cycle when the heart muscle relaxes .
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the process by which cells become specialised for different functions.
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a term applied to cells in which the nucleus contains two sets of chromosomes.
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the movement of molecules or ions from a region where they are in high concentration to one where their concentration is lower.
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discontinuous variation
variation shown when the characters of organisms fall into distinct categories
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ecological niche
The place or function of a given organism within its ecosystem.
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all the living and non-living components of a particular area
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a disease in which the walls of the alveoli break down, reducing the surface area for gaseous exchange, thereby causing breathlessness in the patient
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a protein or RNA that acts as a catalyst and so alters the speed of a biochemical reaction.
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facilitated diffusion
diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across plasma membranes.
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reproductive (sex) cell that fuses wit another gamete during fertilisation.
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section of DNA on a chromosome coding for one or more polypeptides.
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gene pool
the total number of allele in a particular population at a specific time
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globular protein in blood that readily combines with oxygen to transport it around the body. it compromises four poly peptide chains around an iron-containing haem group
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term refering to cells that contain only a single copy of each chromosome e.g. the sex cell (gamete)
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homologous chromosomes
pair of chromosomes, one maternal &one paternal, that have same gene loci &therefore determine the same features. they are not necessarily identical, however, as individual alleles of the same gene may vary. they're capable of pairing during meiosis.
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human genome
the totality of the DNA sequences on the chromosomes of a single human cell.
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the breaking down of large molecules into smaller ones by the addition of water molecules
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interspecific varition
differences between organisms of different species
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intraspecific variation
differences between organisms of the same species.
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solutions that possess the same concentration of solutes and therefore have the same water potential
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nuclear division - number of chromosomes halved
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nuclear division - daughter cells have the same number of chromosomes as the parent cell
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passive immunity
resistance to disease that is acquired from the introduction of antibodies from another individual
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peptide bond
the chemical bond formed between two amino acids during condensation
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small circular piece of DNA found in bacterial cells
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primary structure
the sequence of amino acids that makes up the polypeptides of a protein
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quaternary structure
a number of polypeptide chains linked together, and sometimes associated with non-protein groups, to form a protein
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semi-conservative replication
DNA makes exact copies of itself by unwinding the double helix so that each chain acts as a template for the next. the new copies, therefore, possess the original and one new strand of DNA.
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the stage in the cardiac cycle when the heart contracts
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Card 2


active immunity


resistance to disease resulting from the activities of an individual's own immune system whereby an antigen induces plasma cells.

Card 3


active site


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Card 4


active transport


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Card 5




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