Question

What purpose is served by the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase as the first step in glycolysis?

a. It generates a high-energy phosphate bond
b. It converts ATP to a more useful form
c. It helps drive the uptake of glucose from outside the cell.
d. It is the first committed step of glycolysis.
e. It enables the glucose 6-phosphate to be recognized by aldolase, the next enzyme in the glycolytic pathway.

Answer 1

The phosphorylation of glucose by hexokinase in glycolysis converts glucose into a more reactor glucose 6-phosphate, traps it inside the cell, and maintains a concentration gradient, making this the first committed step in glycolysis.

Step-by-step explanation:

The purpose served by the phosphorylation of glucose to glucose 6-phosphate by the enzyme hexokinase as the first step in glycolysis is manifold. Firstly, it makes the glucose molecule more reactive, priming it for subsequent steps in the glycolysis pathway. Additionally, the phosphorylation prevents the glucose from exiting the cell as the phosphate group adds a negative charge, preventing the molecule from crossing the hydrophobic plasma membrane. This effectively traps the glucose within the cell, ensuring that it is available for cellular metabolism and maintaining a concentration gradient across the plasma membrane. Consequently, this step is considered the first committed step in the glycolytic pathway. It does not, however, directly involve the recognition of glucose-6-phosphate by aldolase — that comes later in the pathway.