BIOL1004 Study Guide - Final Guide: Thymine, Nitrogenous Base, Covalent Bond
Enzymes
• Reactants/substrated bind to enzyme active site
• Binding depends on the complementary shapes (lock and key model)
• In some cases the binding of a substrate might induce the enzyme to adjust its
shape, leading to a better fit (induced fit model)
• Break → rearrange → reform chemical bonds
EXAMPLE:
• Phenylalanine hydroxylase
o Phenylalanine —> tyrosine
• Defect means the conversion cannot take place
• Phenylalanine builds up and may be converted to other metabolites not usually
present at significant levels → brain damage → mental retardation
• Can be avoided if detected at birth and the baby is given a special diet
containing minimal amount of phenylalanine
• Can be detected by smell of phenylalanine metabolites in urine
Characteristics
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• Optimal temperatures
• Optimal pH
o Can change the charge on amino acids of which enzymes are
composed → perturb the ionic interactions that contribute to holding
enzymes in a particular shape
o Changes in the charges of enzymes at the active site can have a
particular dramatic affect
• When tertiary structure has been destroyed —> denatured
• Working at maximum rate → saturated
Cofactors and co enzymes
• Small, non-protein molecules, bind to enzymes and thereby facilitate their
activity.
• Some cofactors are inorganic metal ions e.g. zinc, copper or iron atoms.
• Others are organic molecules (i.e. carbon-containing molecules such as
vitamins) in which case they are called coenzymes.
Inhibition
Many drugs are enzyme inhibitors e.g. aspirin
Allosteric regulation
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Document Summary
Enzymes: reactants/substrated bind to enzyme active site, binding depends on the complementary shapes (lock and key model) In some cases the binding of a substrate might induce the enzyme to adjust its shape, leading to a better fit (induced fit model: break rearrange reform chemical bonds. Molecules or ions bond to a site different from the active site (allosteric site) and cause the activity of the enzyme to increase or decrease. Purines- six membered ring fused to five member ring: nitrogenous base, sugar, phosphate group, without phosphate group nucleoside. Example: atp: major source of energy for all biological processes in all organisms is the energy released by breaking the phosphate-phosphate bonds of atp (hydrolysis). Example: cyclic amp is formed from atp and serves as a second messenger" (i. e. an intracellular signalling molecule) inside cells: the conversion of atp to camp is via the enzyme adenylate cyclase.
