Enzymes
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metabolism
the collection of all biochemical reactions in an organism
enzyme
globular proteins with a specific tertiary structure which act as biological catalysts speeding up the rate of a reaction by lowering the activation energy
activation energy
the amount of energy required for a reaction to proceed
bonds present in tertiary structure
hydrogen disulphide ionic hydrophobic/philic interactions
anabolic reaction
metabolic reaction involving formation of bonds. Eg. photosynthesis
catabolic reaction
metabolic reaction involving breaking of bonds. Eg. respiration
active site
the functional part of an enzyme
lock and key model
substrate fits to active site as they are complementary shapes to form an enzyme-substrate complex products released will no longer fit the active site
induced fit model
substrate and enzyme are NOT complementary shapes. when a substrate bind the active site changes shape to fit the substrate. placing strain on the substrate and distorting the bond, lowering activation energy. when products are released the active site changes back to original shape
properties of enzymes
specific fast acting soluble
why are enzymes soluble
their hydrophilic R groups are on the outside of the molecule
why are enzymes specific
due to the order and sequence (primary structure) of amino acids that make up their active site.
what are the 5 factors affecting enzyme action
temperature pH substrate concentration enzyme concentration inhibitors
what are the two types of inhibitors
competitive and non-competitive
what does extreme pH do to an enzyme
denatures enzyme by altering the electrostatic charge the side chains of the amino acids. if the active site has too many H+ ions (acidic) or OH- ions (alkali) then the enzyme will repel the substrate
how do competitive inhibitors reduce rate of reaction
its shape is complementary to the active site and so it binds to it blocking the substrate meaning less enzyme-substrate complexes can form
what point does the non-competitive inhibitor bind to
allosteric site
an example of non-competitive inhibitor
cyanide
an example of competitive inhibitor
Malonic acid
immobilised enzymes
enzymes that are fixed, trapped or bound on an inert matrix
how are enzymes immobilised
absorption onto insoluble matrix covalent binding to solid trapped within gel encapsulated behind semi permeable membrane
advantages of immobilised enzymes
easily recovered for re-use product not contaminated with enzyme increased stability over a wider range of ph increased stability over a range of temperatures several enzymes with different temperature or ph optimums can be used in one process enzymes can be easily added or removed
allosteric site
a point on an enzyme that is not the active site
competitive inhibitor
an inhibitor that is similar in shape to a substrate