1. Enzymes Chemical Reactions

2. Chemical reactions are constantly taking place in your cells Reactants  Products Chemical reactions involve making and breaking bonds

3. Chemical Reactions There is always a change in energy Endergonic – energy goes in (reactant) Exergonic – energy is released (product) Activation energy – energy needed to start a reaction Factor in all reactions

4. Energy in Reactions

5. Reactions in Living Things Some chemical reactions in living things are too slow or have activation energies that are too high Not practical for living things

6. Catalysts Luckily, cells make catalysts – substances that speed up reactions by lowering activation energy Catalysis – process of influencing chemical bonds in a way that lowers activation energy

7. Enzymes Proteins that act as biological catalysts to speed up chemical reactions Can be up to millions of times faster! Very specific; usually only catalyze one reaction

8. Enzyme-Substrate Complex Substrates – reactants in an enzyme-catalyzed reaction Substrate(s) bind to enzymes at a specific location called an active site The substrate must precisely fit into the site Shapes are complementary Often compared to lock and key Also called “induced fit”

9. Process - EnzymesEnzymes 1. Substrate fits into the active site on the appropriate enzyme 2. Intermolecular forces form enzyme- substrate complex 3. Reactions takes place until complete 4. Products are released and the enzyme is free from substrate to begin process again

10. Enzyme-Substrate Complex

11. Enzymes Thousands of different kinds of enzymes Found in different types of cells Contributes to structural and functional variations among cell types Enzymes in a cell determine the course of metabolism – a collection of all the chemical reactions in a cell

12. Enzyme Regulation Many factors can affect enzyme action Concentration of enzyme and substrate Temperature – Increase can increase rx. rate Most have an optimum temp. of 35-40 o C pH – most have optimum pH from 6-8 However, extremes in either condition could cause the enzymes to denature (change shape or unfold) and no longer function

13. Inhibitors Substance that binds to enzyme and decreases activity Two types: Competitive inhibitors – have similar shape as substrate and compete for active site; can prevent or block substrate from binding Noncompetitive inhibitors – bind to the enzyme at a different site and change the shape of the enzyme

14. Inhibition