Enzymes Functions and Control
Enzyme Terms Substrate - the material and enzyme works on. Enzyme names: Ex. Sucrase - ase name of an enzyme - ase name of an enzyme 1st part tells what the substrate is. (Sucrose) 1st part tells what the substrate is. (Sucrose)
Enzyme Name Some older known enzymes don't fit this naming pattern. Examples: pepsin, trypsin BUT…enzymes are proteins (-in = protein)
Active Site The area of an enzyme that binds to the substrate. Structure is designed to fit the molecular shape of the substrate. Therefore, each enzyme is substrate specific.
Models of How Enzymes Work 1. Lock and Key model 2. Induced Fit model
Lock and Key Model Substrate (key) fits to the active site (lock) which provides a microenvironment for the specific reaction.
Induced Fit Model Substrate “almost” fits into the active site, causing a strain on the chemical bonds, allowing the reaction to proceed.
Substrate Active Site
Factors that Affect Enzymes Environment Cofactors Coenzymes Inhibitors Allosteric Sites
Environment Factors that change protein structure (denature) will affect an enzyme. Examples: pH shifts temperature salt concentrations
Cofactors Non-protein helpers for catalytic activity. Examples: Iron Zinc Copper
Coenzymes Organic molecules that affect catalytic activity. Examples: vitamins
Enzyme Inhibitors Competitive - mimic the substrate and bind to the active site. Noncompetitive - bind to some other part of the enzyme.
Allosteric Regulation Cell’s can’t have enzymes turned on all the time The control of an enzyme complex by the binding of a regulatory molecule. Regulatory molecule may stimulate or inhibit the enzyme complex by causing it to change shape. Works like a reversible non-competitive inhibitor
Allosteric Regulation
Feedback Inhibition The end product of a metabolic pathway affects the function of an enzyme A metabolic pathway is switched off by the inhibitory binding of its end product to an enzyme that acts early in the pathway Usually allosteric regulation