Chapter 2, Section 4

1. Chapter 2, Section 4 Chemical Reactions & Enzymes (p. 49-53)

2. Metabolism • Combination of all chemical reactions necessary for maintaining life. • Chemical reactions change molecules into new ones by:

3. Activation Energy • Energy required to start a chemical reaction • Amount depends on type of chemical reaction

4. How to Increase Chemical Reaction Speeds? • Increasing temperature causes molecules to move around faster • PROBLEM: biological systems are sensitive to temperature changes • SOLUTION: enzymes are biological catalysts without changing the system’s temperature

5. What Are Enzymes? • Enzymes are proteins that speed up chemical reactions • Decrease activation energy • Creates new reaction pathway

6. How Do Enzymes Work? • Substrate(s)/reactants enter the active site • Known as induced fit OR “Lock and key” model • Lowers activation energy • Bringing reactant molecules close together • Placing stress on bonds that need to be broken • Products released from active site • Enzyme reverts to original shape and can receive another substrate

8. Enzyme Reaction Rates • Measured in the formation of products over time • Rate = (Y2-Y1)/(X2-X1) • Factors that impact an enzyme’s reaction rate • Substrate concentration • Competitive inhibitor • pH • Temperature

9. Substrate Concentration • Reaction rate will increase as substrate rate increases until it hits its saturation point • Point when all enzymes are being used

10. Competitive Inhibitor • Molecule with a similar shape as substrate block active site on enzyme • Decreasing enzyme reaction rate

11. Enzyme’s Shape Role in Reaction Rate • Recall that all proteins have a highly specific 3D shape that they fold into • They are ONLY able to function while in this shape • The specific shape of the protein determines the shape of the active site • All enzymes function within a narrow range of optimal pH and temperature • pH and temperature outside of the optimal range can cause enzyme denaturation (change in shape) • Enzyme denatures, is unable to bind substrate • Reaction rate slows/eventually stops

12. pH • Different types of enzymes have different optimum pH levels • Denaturation can occur outside of optimum levels

13. Temperature • As temperature increases, enzyme reaction rate increases UNTIL it passes the optimal range • Denaturation happens after max temperature