Enzymes

1
Enzymes Chemical Reactions!
2
Enzyme Definitions

• Enzyme- biological catalyst that speeds up the
  rate of reaction (rxn) by lowering the activation
  energy (EA)
• EA- energy necessary to initiate a rxn
• Substrate- the substance on which the enzyme acts
• Active Site- the portion of the enzyme where the
  substrate binds to start the rxn
• Coenzyme- nonprotein molecules that facilitate
  enzymes role (ex. Vitamins)

3
Enzyme-Substrate Interactions

• Substrate specific- "Lock Key" fit (very
  specific!)
• Induced Fit- the new version of the Lock Key
  model which states that the active site of an
  enzyme may actually change in order to fit a
  substrate
• Allosteric Site- site on the enzyme away from the
  active site where a molecule (not the substrate)
  binds to change the shape of the active site?
  substrate can no longer bind? no rxn

4
Feedback Inhibition
5
Feedback Inhibition cont
6
Activation Energy
Normal rxn Will occur more Slowly!
Enzymes lower EA of the rxn? Speed it up!!!
7
Denaturing Enzymes

• Enzymes are not changed nor used up during a
  chemical rxn
• Heat, salt, sunlight, change in pH
  (acid/base) may denature an enzyme
• Denature- to change the shape of an enzyme so it
  can no longer bind to its substrate? no rxn?

8
Exergonic vs. Endergonic Rxns
Energy is released out to environment!
Energy is put into rxn in order for it to take
place!