GCE O Level Biology: Movement of Substances, Enzymes and Nutrients

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Diffusion
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Terms in this set (21)
Diffusion
Net movement of molecules from a region of their higher concentration to a region of their lower concentration, down a concentration gradient
Image: Diffusion
Osmosis
Movement of water molecules from a region of higher water potential to a region of lower water potential, across a partially permeable membrane
Image: Osmosis
Water potential
A measure of the tendency of water to move from one place to another
Concentration gradient
Difference in concentration between two regions
Plasmolysis
Shrinking of cytoplasm away from the cell wall when the plant cells are immersed in a solution more concentrated than their cell sap
Image: Plasmolysis
Turgor pressure
Pressure exerted outwards on the plant cell wall due to the water in the cell, giving the cell its turgidity.
Image: Turgor pressure
Active transport
Process in which energy from respiration is used to move molecules against a concentration gradient, from a region of lower concentration to a region of higher concentration
Image: Active transport
Condensation reaction
A chemical reaction in which two simple molecules are joined together to form a larger molecule with the removal of one molecule of water
Image: Condensation reaction
Hydrolysis
A chemical reaction in which water molecule is needed to break up a complex molecule into smaller molecules
Image: Hydrolysis
Reducing sugars
Sugars which can reduce the copper (II) to copper (I) E.g. glucose, maltose, fructose, lactose
Image: Reducing sugars
Saturated fatsFats with straight fatty acid chains and are found mostly in animalsUnsaturated fatsFats with bent fatty acid chains and are found mostly in vegetablesEmulsionA suspension of small drops of a liquid in another liquidKwashiorkorProtein-deficiency disease in which children have swollen stomachs and dry, scaly skinEnzymesBiological catalysts made with proteins which alter the rate of chemical reactions without themselves being chemically changed at the end of the reactionsActivation energyEnergy needed to start a chemical reactionActive siteDepression on the surface of an enzyme molecule into which the substrate molecule can fitOptimum temperatureTemperature at which enzyme is most active, catalysing the largest number of reactions per secondOptimum pHpH value at which enzyme is most active, catalysing the largest number of reactions per secondDenaturationChange in the three-dimensional structure of an enzyme or any other soluble protein, caused by heat or extreme pH changesLimiting factorAny factor that directly affects a process if its quantity is changed