Metabolism

Enzymes: review

Anabolism vs Catabolism

What is necessary for a chemical reaction to begin?

Reactant(s) must come together in the right orientation With enough energy So ho do enzymes catalyze this process?

Lowers activation energy Template for proper orientation of substrates As active site “holds” substrate – can stress/strain the substrate, breaking bonds More conducive microenvrionments – ie altering pH

Enzyme specificity What contributes to it?

Complementary fit

Lock and Key Model

Induced Fit Model (replaces lock and key) Enzymes = globular proteins Shape shifters – subtle Active site is not rigid Can fit more snugly around substrate

Catalysis Saturation – limiting factor = max enzymatic rate

Enzyme efficiency Determined by environmental factors Optimal conditions

Cofactors Nonprotein helpers Zinc, iron, copper Vary in how they bind to enzyme Perform a critical function in catalysis

coenzymes Organic cofactors Most vitamins

Other factors influencing reaction rate… inhibitors Reversibility

Competitive inhibition

Noncompetitive inhibition

examples Sarin: nerve gas DDT and parathion antibiotics

Regulation Selective inhibition Cells control when and where enzymes are active control the building of the protein Control the protein once its built

Allosteric regulation Protein function at one site is affected by the binding of a regulatory molecule to a separate site Can inhibit or stimulate