Enzymes and Speeding Up Reactions

How does an enzyme speed up a reaction

• Lowers the transition state so more molecules can be accepted by the enzyme

  • Lower energy requirement

  • Product more stable

  • Spontaneous

Spontaneous

Product always at lower energy then substrate

Gree energy of activation

Total energy in the system

4 separate stages of enzymatic reactions

1. Substrate and enzyme are in solution to interact

2. Interaction takes place and substrate changes shape and size. About to reach transition state.

3. Further change in molecule while it continues to interact with the enzyme. Past transition state

4. Enzyme and the product substrate separate

Lock and Key Hypothesis

(Hermann) Emil Fischer 1890

• Enzyme Active Site Exactly Complimentary to Shape of Substrate

• Explains why enzymes are so specific

Lock and Key Hypothesis disadvantages

1. If exact fit, energy is reduced when they combined into a complex meaning they need even more energy to reach transition state

2. Enzymes can reverse the product back to a substrate but can’t in this theory because it’s the exact fit for the substrate not the product. (Non-Reversable)