Enzymes

Question 1

What is a Cofactor of an enzyme?

Answer 1

Non-protein component of an enzyme needed for activity

Question 2

What is a Coenzyme?

Answer 2

Complex organic molecule

Question 3

What is a coenzyme produced from?

Answer 3

A vitamin

Question 4

What is a prosthetic group?

Answer 4

A type of Cofactor covalently bound to the enzyme

Question 5

What is an apoenzyme?

Answer 5

The protein component of an enzyme that contains a prosthetic group

Question 6

What is Vmax?

Answer 6

Maximum rate achieved by the enzyme system

Question 7

What is the Km?

Answer 7

The substrate concentration when reaction rate is half Vmax

Question 8

What is the Vo?

Answer 8

Initial velocity of an enzyme reaction

Question 9

What is the Michaelis Constant?

Answer 9

Km=k-1 + k2/k1

Question 10

What does a large Km indicate?

Answer 10

A less stable ES complex (complex formed between enzyme and substrate)

Question 11

What does a low Km indicate?

Answer 11

A more stable ES complex

Question 12

What does the Michaelis Constant tell us?

Answer 12

The affinity of an enzyme for a substrate.

Question 13

How does a competitive inhibitor bind to a substrate?

Answer 13

The same way the intended substrate does, at the active site. (Non-covalently)

Question 14

What does competitive inhibition do to Vmax and Km?

Answer 14

Increases Km, Vmax can remain the same

Question 15

How is Competitive inhibition overcome?

Answer 15

By increasing the concentration of the intended substrate

Question 16

How does a non-competitive inhibitor bind to a substance?

Answer 16

Bind non-covalently to a site other than the active site

Question 17

What does non-competitive inhibition do to Km and Vmax?

Answer 17

Km is unchanged (substrate can still bind to active site) but Vmax decreases as the inhibitor can’t be displaced.

Question 18

The concerted and Sequential models are examples of what?

Answer 18

Allosteric enzymes

Question 19

What kind of inhibition do allosteric enzymes produce?

Answer 19

Non-Competitive inhibition

Question 20

Explain the concerted model

Answer 20

Sub units, in 2 different conformations (low Km and high Km)
Enzyme flips between conformations
When 1 substrate binds this causes the other units to hold an open conformation for more substrate, increasing affinity.

Question 21

Explain the sequential model

Answer 21

No flipping between states
Binding to a substrate causes conformational change in 1 subunit
This causes a change in the next subunit which makes further binding easier