L11: Enzymes II

Question 1

Effect of Km & Vmax on competitive inhibitors

Answer 1

Increase Km
Don’t change Vmax

Question 2

Effect of Km & Vmax on non-competitive inhibitors

Answer 2

Don’t change Km
Decrease Vmax

Question 3

Action of competitive & non-competitive inhibitor on enzyme

Answer 3

Competitive: Block enzyme active site

Non-competitive: Interfewe in some other way with catalytic mechanism

Question 4

Define irreversible enzyme inhibitors

Answer 4

Substance that permanently blocks the action of the enzyme

Question 5

Example of irreversible enzyme inhibitors

Answer 5

AChE (Acetylcholinesterase) inhibitors

Question 6

Define allosteric regulation

Answer 6

Substance that binds to a site on enzyme distinct from the active site

Question 7

Define allosteric enzymes-kinetics

Answer 7

Conformational change between low affinity ‘T-state’ and high affinity ‘R-state’

Question 8

How is activity of allosteric enzymes modulated?

Answer 8

By allosteric activators/inhibitors

Question 9

Role of positive allosteric modulator

Answer 9

Lowers concentration of substrate where enzymes reaches half its Vmax

Question 10

Role of negative allosteric modulator

Answer 10

Increases concentration of substrate where enzymes reaches half its Vmax

Question 11

Define reversible inhibition

Answer 11

Inactivates an enzyme through non-covalent interactions

Question 12

Define irreversible inhibition

Answer 12

Permanently blocks action of an enzyme

Question 13

Define ATCase

Answer 13

The binding of substrate to one active site in a molecule increases the likelihood that the enzyme will bind more substrate

Question 14

Two forms of the enzyme ATase

Answer 14

1) T (tense) state: Absence of substrate

2) R (relaxed) state: Observed when substrate binds