Enzyme s

The Need for Enzymes Many important exergonic rxns require more E A than cells can provide Other rxns require specific collision angles, slowing rxn rate

Lowering E A Enzymes lower E A to a level that’s safe and attainable

Catalysis 1. Enzyme binds substrate(s) at active site 2. Enzyme changes shape to separate or combine molecules 3. Enzyme reverts to original shape

Specificity Enzymes are substrate specific –3-D shape makes enzymes specialized –An enzyme binds substrate(s) at active site ActiveSite

Rate of Rxns As [substrate] ↑, Rate ↑ [substrate] Rate EnzymeSaturation

Rate of Rxns Temperature –As temp ↑, collisions are more frequent (rate ↑) –At high temps, h-bonds break, changing enzyme shape (rate ↓) Temperature Rate Denaturation Optimal Range

Rate of Rxns

Enzyme Regulation Molecules bind to enzymes to alter their functions Activation –Cofactors Nonprotein helpers Coenzymes – Organic cofactors –Cooperativity Substrate = Activator

Enzyme Regulation Active Site Allosteric Site Inhibition –Competitive Blocks active site –Noncompetitive Changes enzyme shape Changes enzyme shape

Enzyme Regulation Feedback Inhibition –Product inhibits enzyme