Chemical Reactions and Enzymes

1. Chemical Reactions and Enzymes

2. Energy in Reactions • Chemical reactions can release energy or absorb energy. • Chemical rxns that release energy often happen spontaneously • Chemical rxns that absorb energy usually don’t happen unless there is a source of energy

3. Examples • 2H2 + O2 2H2O Gives off energy (explosively) • 2H2O  2H2 + O2 (electrolysis – pass electric current through it)

4. Energy • In order to stay alive, organisms need to carry out reactions that require energy • Why do you need energy? • Grow • Breath • Think • Dream • everything

5. Activation Energy • The energy require to start a reaction is called “Activation Energy”

6. Enzymes • Catalysts – substance that speeds up a reaction by lowering the activation energy • Enzymes are proteins that act as biological catalysts • Can accelerate a reaction by a factor of 1010 – 10 billion times faster! • Enzymes are very specific. Usually only one reaction

7. Naming Enzymes • Part of the name of an enzyme usually derived from the reaction it catalyzes • Peptinase – helps peptin break down proteins in your small intestines • Carbonic anhydrase – catalyzes reaction that removes water from carbonic acid • “ase” is usually the suffix of an enzyme

8. Enzyme Action • Reactants must collide with each other with enough energy to break the bonds and form new bonds • Enzymes provide a site where the reactants can be brought together to react

9. Structure • The reactants in an enzyme catalyzed reaction are called substrates • Each protein has a specific, and complex shape • Active site is where the reactants bind to the enzyme • The active site and the reactants have complementary shapes – sometimes called “Lock and Key”

10. Activation Energy Reaction pathway without enzyme Activation energy without enzyme Activation energy with enzyme Reactants Reaction pathway with enzyme Products

11. Figure 2-21 Enzyme Action Section 2-4 Enzyme (hexokinase) Glucose Substrates ADP Products Glucose-6- phosphate ATP Products are released Active site Substrates bind to enzyme Enzyme-substrate complex Substrates are converted into products Go to Section:

12. Figure 2-21 Enzyme Action Section 2-4 Enzyme (hexokinase) Glucose Substrates ADP Products Glucose-6- phosphate ATP Products are released Active site Substrates bind to enzyme Enzyme-substrate complex Substrates are converted into products Go to Section:

13. Figure 2-21 Enzyme Action Section 2-4 Enzyme (hexokinase) Glucose Substrates ADP Products Glucose-6- phosphate ATP Products are released Active site Substrates bind to enzyme Enzyme-substrate complex Substrates are converted into products Go to Section:

14. Figure 2-21 Enzyme Action Section 2-4 Enzyme (hexokinase) Glucose Substrates ADP Products Glucose-6- phosphate ATP Products are released Active site Substrates bind to enzyme Enzyme-substrate complex Substrates are converted into products Go to Section:

15. Once done… • Once the reaction is complete, the products are released and the enzyme is free to catalyze another reaction • There are various methods to control enzyme activity • Temperature, pH, and proteins that can turn on or off activity at critical stages