What role do inhibitors play in enzyme catalysed chemical reactions

Question 1

What is an inhibitor

Answer 1

An inhibitor is a substance that can slow down or stop a reaction

The inhibitor combines with the enzyme and stops it from attaching to the substrate

The inhibitor can be reversible or non reversible

Question 2

What are the two main types of inhibitor

Answer 2

Competitive

Non competitive

Question 3

What is the role of a competitive inhibitor

Answer 3

• A competitive inhibitor is similar in structure to that of the substrate
• The competitive inhibitor competes with substrate at the active site
• This prevents the the substrate (Key) from bonding with the active site (lock)

Question 4

What is an example of a competitive inhibition

Answer 4

The enzyme succinate dehydrogenase removes hydrogen from its substrate succinate

However this activity can be blocked if malonate is present

Malonate competes with the substrate succinate for the active site of succrinate dehydrogenase

Question 5

How might the body minimise the impact of competitive inhibitors

Answer 5

Increase the amount of substrates

Question 7

What is the role of a non competitive inhibitor

Answer 7

• Does not bind to the active site
• It attaches to some other part of the enzyme
• Which changes the 3D shape of the enzyme tertiary structure and the shape of the active site
• The change is permanent
  *

Question 9

What is the difference between a competitive inhibitor and a non competitive inhibitor

Answer 9

• Competitive inhibitors compete with substrates whereas non competitive inhibitors do not
• Competitive inhibitors do not change the shape of the enzyme and the active site whereas non competitive inhibitors do

Question 10

What is the difference between a non competitive inhibitor and a competitive inhibitor

Answer 10

• Non competitive inhibitors change the 3D shape of the enzyme (Tertiary structure) whereas the competitive inhibitors do not
• Non competitive inhibitors do not compete with the substrates at the active site whereas competitive inhibitors do.

Question 11

Is a non competitor reversible or non reversible

Answer 11

Non reversible it changes the tertiary structure and the shape of the active site.

Question 12

What is an example of a non competitive inhibitor (Non reversible)

Answer 12

• Heavy metals such as silver (Ag⁺) and Mercury (Hg⁺) cause the disulfide bonds holding an enzym e together to break
• This alters the 3D shape (Tertiary structure) of the enzyme to change permanently
• This results in the enzyme losing its catalytic capability

Question 13

What is another example of a non competitive (non reversible) inhibitors

Answer 13

• Cyanide is a no competitive inhibitor (Non reversible) of cytochrome oxudase and important enzyme in respiration