Catalysis and Enzymes

Question 1

What is a catalyst? What is the name for a biological catalyst? What is rule for reactions to be catalyzed?

Answer 1

A catalyst is any substance that speeds up a chemical reaction without itself being used up

• A biological catalyst is called an enzyme
• Only reactions with overall negative dG can be catalyzed

Question 2

Do catalysts change dG value?

Are they used up in a reaction?

Answer 2

Catalysts do not change dG value. A catalyst is also not used up in a reaction.

Question 3

How do enzymes work?

Answer 3

Enzymes lower the Activation energy of reactions.
At 37 degrees, most spontaneous reactions don’t proceed.
- Reactants (substrates) bind to active site of enzyme (creates enzyme-substrate complex), this causes enzyme to undergo a shape change which brings substrate into a transition state.
Transition state is characterized by lower activation energy, which speeds up reaction
- As soon as the products leave the active site, the enzyme reverts to its original state.

Question 4

What is a cofactor?

Answer 4

Some enzymes require a cofactor to function

- Can be metal ions, small organic molecules, … They help the enzyme function

Question 5

What are the two types of enzyme inhibition?

Answer 5

Competitive (inhibitor binds to active site) and allosteric (inhibitor binds somewhere other than active site and changes shape of active site)