Question

Figure given below shows three velocity - substrate concentration curves for an enzyme reaction. What do the curves depict?

• A. $a$-normal enzyme action, $b$-competitive inhibition, $c$-noncompetitive inhibition
• B. $a$-enzyme with an allosteric modulator added, $b$-normal enzyme activity, $c$-competitive inhibition
• C. $a$-enzyme with an allosteric stimulator, $b$-competitive inhibitor added, $c$-normal enzyme reaction
• D. $a$-normal enzyme reaction, $b$-no competitive inhibitor added $c$-allosteric inhibitor added

Answer 1

The correct option is A $a$-normal enzyme action, $b$-competitive inhibition, $c$-noncompetitive inhibition

Graph a shows that enzyme acts normal in the reaction because it reaches the normal value of Vmax.

Graph b shows that a competitive inhibitor is involved in the reaction because it reaches the normal value of Vmax, but with the higher concentration of substrate to get it there. So the km value is higher.

Graph c shows that a non-competitive inhibitor, the reaction never reach its normal Vmax, as shown in the figure where Vmax is reduced so the concentration of enzyme is reduced.

So the correct answer is A.