ENZYMES

Question 1

Define ‘enzyme’

Answer 1

A biological catalyst which increases the rate of reaction by lowering the activation energy

Question 2

What is the active site of an enzyme?

Answer 2

The place where substrate binds and chemical reaction occurs

Question 3

What is Vmax?

Answer 3

The theoretical maximum rate when ALL active sites are saturated with substrate

Question 4

What is Km?

Answer 4

The substrate concentration that gives HALF of Vmax

Question 5

How does Km relate to enzyme affinity?

Answer 5

Low Km = high affinity for substrate

High Km = low affinity for substrate

Question 6

What is an international unit of enzyme activity (IU)?

Answer 6

1 unit:

Amount of enzyme that converts 1 micro mol per minute under standard conditions

Question 7

What is an enzyme inhibitor?

Answer 7

A molecule which slows down or prevents enzyme reaction

Question 8

Describe the features of a competitive inhibitor

Answer 8

• Competes for active site
• Resembles substrate
• Reduces proportion of enzymes bound to substrate
• Km increases
• Vmax unaffected

Question 9

Describe the features of a non-competitive inhibitor

Answer 9

• Binds at alternative site
• Decreases turnover number of enzyme
• Lowers Vmax
• Km unaffected