Define and use the following terms, providing examples if appropriate: catalyst enzyme, substrate, active site, cofactor, coenzyme, competitive inhibition, noncompetitive inhibition.
Catalyst Enzyme - a substance that speeds up the reaction but is not used up.
Substrate - is the material with which the catalyst reacts, and is modified during the reaction to form a new product.
Active Site - is the region involved in the catalytic reaction of the enzyme.
Cofactor - non-protein substances that usually bind to the active site and are essential for the enzyme to work.
Coenzyme (organic cofactors) - a non-protein compound that is necessary for the functioning of an enzyme .
Competitive inhibition: takes place when a molecule that is structurally similar to the substrate for a particular reaction competes for a position at the active site on the enzyme. Example: Sulfa drugs given to bacteria complete with para-amino benzoic acid (PABA) and folic acid synthesis is inhibited.
Noncompetitive inhibition: the inhibitor binds to a part of the enzyme that is not the active site. Example: Cyanide combines with the prosthetic group of cytochrome oxidase and inhibits the election transport chain.
2. Compare and contrast competitive and noncompetitive inhibition.
Characteristic.
Competitive inhibition.
Non-competitive.
Inhibitor.
Structurally/chemically very similar to substrate.
Different from substrate.
Site of binding.
Active site.
Binds to different site "not active site/allosteric site".
Effect.
Blocks active site.
Changes tertiary structure of enzyme/conformational change of active site.
Effect.
Competes with substrate/prevents substrate binding.
Substrate cannot bind " reaction isn't catalyzed, decreased enzyme activity.
Example.
Folic acid synthesis in bacteria by sulfonamide Prontosil. .
Malonate ions inhibiting the enzyme succinate dehydrogenase.
Metal ions (Hg, Ag, Cu, CN) inhibit enzymes by breaking disulfide linkages.
