Question

Haemoglobin is composed of four subunits. When one subunit binds to oxygen, it increases the chances that the other three subunits will also bind to oxygen. What is this type of activity called?

• A. Inhibition
• B. Cooperativity
• C. Enzyme substrate complex
• D. Catalysis
• E. Activation

Answer 1

The correct option is B Cooperativity

A. When the binding of chemical shuts off the enzymatic activity, the process is called inhibition.

B. When binding of a molecule to the enzyme increase its affinity for more molecules, it is called cooperativity.

C. Binding of the substrate to the active site of enzyme produces a highly reactive short lived complex called Enzyme substrate complex which breaks into chemical products and unchanged enzyme.

D. Catalysis is the increase in rate of reaction by a catalyst.

E. Activation is the start of reaction by an enzyme.

Hence, the increase in affinity of haemoglobin for oxygen by binding of one oxygen molecule, is cooperativity.

So, the correct answer is 'Cooperativity'.