NEETBotanyBiomolecules (B)
In a laboratory experiment, the rate of conversion of succinate to fumarate by the enzyme succinate dehydrogenase is measured. The concentration of the enzyme is kept constant while the concentration of the substrate, succinate, is progressively increased from a very low level to a very high level. Which of the following best describes the expected trend in the velocity of this reaction?
Options
- AThe velocity increases indefinitely in direct proportion to the succinate concentration.
- BThe velocity increases initially but eventually plateaus at a maximum value.
- CThe velocity increases to a peak and then declines as succinate concentration becomes too high.
- DThe velocity remains constant from the beginning regardless of the succinate concentration.
Correct answer
B. The velocity increases initially but eventually plateaus at a maximum value.
Step-by-step solution
Succinate dehydrogenase is an enzyme and follows standard enzyme saturation kinetics. With an increase in substrate (succinate) concentration, the velocity of the enzymatic reaction rises steeply at first. However, the reaction ultimately reaches a maximum velocity ( V_ max ) which is not exceeded by any further rise in the concentration of the substrate. This occurs because the number of enzyme molecules is fixed and fewer than the substrate molecules at high concentrations. Once all the active sites of the enzyme