Question

The figure given above shows three velocity-substrate concentration curves for an enzyme reaction. What do the curves 1, 2 and 3 depict respectively?

• A. 1 - Normal enzyme reaction, 2 - Competitive inhibition, 3 - Non-competitive inhibition
• B. 1 - Enzyme with an allosteric modulator added, 2 - Normal enzyme activity, 3 - Competitive inhibition
• C. 1 - Competitive inhibition added, 2 - Enzyme with allosteric substance, 3 - Normal enzyme reaction
• D. 1 - Normal enzyme reaction, 2 - Non-competitive inhibitor added, 3 - Allosteric inhibitor added

Answer 1

The correct option is A 1 - Normal enzyme reaction, 2 - Competitive inhibition, 3 - Non-competitive inhibition

For such doubts remember a thumb rule that, for any enzymatic reaction, higher is initial velocity, V${}_0$ higher will be the rate of reaction.

Now, based on this fact;

A non-competitive inhibition reaction reduces enzymatic activity so it reduces the rate of reaction and hence initial velocity, V${}_0$ reduces as well leading to most reduced V${}_0$.

For any normal enzyme reaction, the enzymatic activity will be higher so the rate of reaction is higher leading to highest initial velocity, V${}_0$

So, the correct answer is '1 - normal enzyme reaction, 2 - competitive inhibition, 3 - non-competitive inhibition'.