Enzymes

Enzymes

Structure
1. each reaction requires a specific enzyme
2. globular proteins that act as catalysts
3. Active site: the area involved in a reaction
  1. complementary in shape to substrate
    1. enzyme-substrate complex
      1. chemically changes the substrate by breaking bonds within, the substrate changes shape and no longer first substrate
Models
1. Lock and Key
  1. complementary to one enzyme
    1. substrate molecules - free kinetic energy -collide with active site
      1. bonds break and end product formed
  2. suggest that enzyme works like a lock and operated like a key
2. induced fit
  1. suggest that enzyme's active site is similar to but not fully complementary to the substrate
  2. Substrate binds to enzyme, active site changes shape to become complementary to substrate
    1. this explains how activation energy is lowered, as the enzyme changes shape it puts pressure on the bonds of the substrate lowering the activation energy
      1. also explains why other molecules can affect enzyme activity
Factors effecting enzyme activity
1. A change in shape of active site
2. A change in the number of collisions
Effect of Temp. on Enzyme
1. Above 40 degrees.
  1. kinetic energy causes enzymes to vibrate
    1. hydrogen bonds break, tertiary shape changes enzyme denatures
2. At 40 degrees
  1. more kinetic energy, more change of collisions, more e-s complexes, more product, ROR increased
Effect of pH on enzyme
1. if higher than optimum pH, denatures due to Hydrogen AND Ionic bonds breaking
Competitive Inhibitors
1. similar in shape
2. competes for active site
3. Fewer enzyme substrates
4. lowers rate of reaction
Non competitive inhibitors
1. different in shape to substrate
2. binds away from active site
3. changes active site
4. no enzyme-substrate complex

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