Question

Hexokinase catalyzes the reaction between glucose and ATP to form glucose 6-phosphate and ADP. The table below summarizes the results of experiments using purified hexokinase. In the experiments, different sugars were substituted for glucose, and the rate of each catalytic reaction was measured and divided by the rate of reaction using glucose as substrate. These data provide evidence for which general statement that has been made about enzymes?
Substrate Relative rate compared with using glucose as substrate

Glucose 1.0
Arabinose 0.1
Mannose 0.4
Galactose 0.02
Xylose 0.0

a. Enzymes are able to speed up a reaction by lowering its activation energy.b. Enzymes display high specificity with respect to their substrates.c. Enzymes often require cofactors and/or coenzymes in addition to their substrates.d. Enzymes bind substrates at their active sites using noncovalent forces of attraction.e. Enzymes lower activation energy of a reaction by stabilizing the substrate’s transition state.

Answer 1

Answer:

The correct answer is option b. "Enzymes display high specificity with respect to their substrates".

Explanation:

One of the characteristics of most enzymes is their high specificity towards their substrates. This is illustrated in the experiment herein stated. Glucose is the main substrate of Hexokinase, since it catalyzes the reaction between glucose and ATP to form glucose 6-phosphate and ADP. In this experiment, different sugars were substituted for glucose in Hexokinase's reaction , and the results show that the relative rate of reaction was reduced to 0.4 in the case of mannose, and up to 0.0 in the case of xylose. Since no sugar was able to have the same relative rate of reaction as glucose, we can conclude that Hexokinase is highly specific to its substrate.