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  • Created by: Molly
  • Created on: 08-05-13 17:34

Activation Energy

The energy required to bring about a chemical reaction;lowered by the presence of enzymes.

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Active Site

The specific portion of an enzyme into which the substrate fits by means of weak chemical bonds.

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Active Transport

The movement of a substance across a membrane against a concentration gradient. The process requires energy (ATP).

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Adenosine Triphosphate

An activated nucleotide found in all living cells that acts as an energy carrier.

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The association of a biomolecule such as an enzyme with a transducer which produces an electrical signal in response to substrate transformation.

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Cell cycle

A sequence of events that takes place from one cell division until the next.

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The green pigment located within the chloroplasts of plants.

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A threadlike, gene-carrying structure found in the nucleus.

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A group of genetically identical organisms formed from a single parent as a result of asexual reproduction.

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The attraction between molecules of the same type.

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Competitive inhibitor

A chemical that reduces the rate of activity of an enzy by having a molecular shape similar to that of the substrate, competing with it for the active site of an enzyme.

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Condensation reaction

Chemical process in which two molecules combine to form a more complex molecule with the elimination of water.

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Crossing over

The reciprocal exchange of genetic material between non-sister chromatids during meiosis.

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The entire contents of the cell, excluding the nucleus and bounded by the plasma membrane.

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The process by which cells become specialised for the different functions.

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The passive movement of a substance down a concentration gradient from a region of high concentration to a region of low concentration.

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Diploid cells

A cell containing two sets of chromsomes, one set inherited from each parent.

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The engulfing material by the plasma membrane bringing it into the cell inside the vescicle.

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A protein that acts as a catalyst, altering the rate of chemical reaction without being used up by the reaction. 

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Ester bond

A bond formed between glycerol and fatty acids.

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Eukaryotic cell

A cell with a membrane-bound nucleus and membrane-bound organelles.

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The release of substances contained in a vesicle from a cell through the cytoplasm.

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Facilitated diffusion

Diffusion involving the presence of protein carrier molecules to allow the passive movement of substances across the plasma membranes.

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A condition where no more water can leave the cell and the cell is said to be plasmolysed.

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A sex cell containing half the number of chromsomes as body cells.

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A length of DNA on a chromosome which codes for a particular polypeptide.

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Glycosidic bond

The link between monosaccharide units.

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Cells that contain only a single copy of each chromosome.

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Homologous chromosomes

A pair of chromosomes that possess genes for the same characters at corresponding loci and therefore determine the same features. One homologous chrosmome is inherited from the father, the other from the mother.

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The breaking down of large molecules into smaller molecules by the addition of water.

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The pressure exerted by a fluid.

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Immobilised enzyme

Enzyme that is fixed,bound or trapped on an inert matrix such as alginate beads.

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Induced fit

The change in shape of the active site of an enzyme so that it binds more snugly to the substrate, induced by the entry of the substrate.

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Intrinsic proteins

Proteins of the cell surface membrane that completely span the phospholipids bilayer from one side to the other.

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Compounds that have the same chemical formula but which differ in the arrangement of the atoms.

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A complex compound by which impregnates the cellulose matrix of plant cell walls, making the wall strong and rigid and impervious to gases,water and solutes.

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A two-stage type of cell division in sexually reproducing organisms that results in gametes with half the chromosme number of the orginal cell.

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Number of cellulose chains packed together.

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A type of cell division in which the daughter cells have the same number of chromsomes as the parent cell.

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Non-competitive inhibitor

A chemical that redces the rate of activity of an enzyme by binding at a position other than the active site altering the overall shape of the enzyme.

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A complex chemical made up fo an organic base,a sugar and a phosphate.

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The chromosme-containing organelle of a eukaryotic cell.

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The net movement of water molecules across a selectively permeable membrane from a region of high water potential to a region of lower water potential.

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Pentose sugar

Possessing five carbon atoms.

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Peptide bond

The chemical bond formed between two amino acids following condensation.

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Mechanism by which cells transport large particles across the plasma membrane into the cell.

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The process in green plants by which C02 and water combine using light energy to form glucose and water.

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Long chain of repeating monomer units.

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Selective permeability

A property of bilogical membranes which allows some substances to cross.

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Sister chromatids

Replicated forms a chromosome joined together by a centromere and eventually seperating during cell division.

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A condition in the cell where no more water can enter. Additional entry of water is prevented by the cell wall stopping further expansion of the cell.

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Water potential

The tendency of a solution to gain or lose water; water moves from a solution with high water potential to one with low water potential. Water potential is decreased by the addition of solute and increased by the application of pressure. Pure water has a water potential of 0.

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The diploid product of the fusion of haploid gametes in sexual reproduction.

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