Enzyme inhibitor

Question 1

What does it mean by a ‘reversible’ inhibitor?

Answer 1

The inhibitor can be released from the enzyme to resume the enzymes’ function

Question 2

Most competitive inhibitors are reversible or irreversible?

Answer 2

Reversible

Question 3

Explain how Vmax of the enzyme can be unchanged in competitive inhibition.

Answer 3

• By adding more substrates to outcompete inhibitors
• More substrates leads to more successful collisions between enzymes and substrates, hence more ESC formed
• Therefore less enzymes available for inhibitors to bind

Question 4

What types of inhibitor does aspirin belong to?

Answer 4

Irreversible, competitive

Question 5

Explain the difference between competitive and non-competitive inhibition mechanisms.

Answer 5

• Competitive: inhibitor binds to active site → substrate can no longer bind to AS
• Non-competitive: inhibitor binds to a location other than the active site (allosteric site) → changes 3o structure, hence change AS shape

Question 6

Explain how an increase in substrate concentration affects the rate of reaction in non-competitive inhibition.

Answer 6

No change, as active site is altered by inhibitor binding in allosteric side

Question 7

State two examples of irreversible, non-competitive inhibitors for human use.

Answer 7

• Organophosphates → insecticides and herbicides (inhibits AChE)
• Proton pump inhibitors (PPIs) → treat long term indigestion

Question 8

What is end-product inhibition?

Answer 8

The product of an enzyme-catalysed reaction acts as the inhibitor

Question 9

How does ATP regulate its own production by end-product inhibition?

Answer 9

• ATP binds to the allosteric site of PFK
• Prevent second phosphorylation of glucose
• Glucose is not broken down to produce more ATP