IB DP Biology-C1.2 Cell respiration -FA 2025- IB Style Questions For HL Paper 1

Ans. D

The results suggest that Inhibitor 1 and the substrate have similar effects on the enzyme-catalyzed reaction, as indicated by the similar shapes of their respective curves in the graph. This could mean that Inhibitor 1 may compete with the substrate for binding to the enzyme’s active site, a characteristic of competitive inhibition.

In competitive inhibition, as the concentration of the substrate increases, it is more likely to bind to the enzyme, overcoming the effects of the inhibitor. This results in a rate of reaction that initially increases with substrate concentration, much like the substrate alone, until the enzyme’s active sites are fully occupied. However, beyond a certain substrate concentration, the rate of reaction may level off because all the enzyme active sites are saturated, and increasing substrate concentration further has no effect.

If Inhibitor 1 behaves as a competitive inhibitor, the graph would show an increase in reaction rate as substrate concentration rises, similar to the pattern observed for the substrate alone, but the maximum rate of reaction (V_max) may be lower due to the presence of the inhibitor.