MB - Controlling Enzyme Activity

Question 1

Why do enzymes have different optimum pH values?

Answer 1

Enzymes are adapted to their function and have specific optimum pH values

Question 2

What are the 2 ways enzymes are covalently regulated?

Answer 2

1. Enzymes inactive due to polypetide blockage. Protease cleaves off chain and activates enzyme (irreversible)
2. Phosphate groups can be used to switch on/off enzymes, using Kinases and Phosphatases (reversible)

Question 3

What stage does K type regulation affect?

Answer 3

The E + S binding stage

Question 4

What stage does V type regulation affect?

Answer 4

ES –> E + P (Catalysis stage)

Question 5

What is enzyme cooperativity?

Answer 5

Where the substrate binding to one active site increases affinity at another site in a different enzyme

Question 6

What are allosteric enzymes?

Answer 6

Enzymes that have an additional binding site for effector molecules other than the active site. (Can act to activate or inhibit enzymes)

Question 7

What are enzyme inhibiters?

Answer 7

Molecules which reduce enzyme activity

Question 8

What are 2 examples of irreversible inhibitors?

Answer 8

1. Aspirin
2. Penicillin

Question 9

What is the difference between competitive and non-competitve inhibition?

Answer 9

Competitive inhibitors have the same shape as the active site and so block substrate from entering.
Non-competitive binds to another site and prevents binding of substrate to the active site

Question 10

How does the Vmax and Km value differ to its normal value during competitive/non-competitive inhibition?

Answer 10

Competitive:
1. Vmax is the same
2. Km seems to be larger
**Non-competitive: **
1. Vmax seems to be smaller
2. Km is the same

Question 11

What do uncompetitive inhibitors bind to?

Answer 11

Only to the enzyme-substrate complex

Question 12

When does the M-M curve become sigmoidal?

Answer 12

When more than 1 active site is present