Which enzyme is crucial for initiating glycolysis by phosphorylating glucose?

The enzyme crucial for initiating glycolysis by phosphorylating glucose is hexokinase. This enzyme catalyzes the first step of glycolysis, where glucose is converted to glucose-6-phosphate. The phosphorylation of glucose is essential because it serves two primary purposes: it traps glucose within the cell and prepares it for further breakdown in the glycolytic pathway. By adding a phosphate group to glucose, hexokinase prevents glucose from easily diffusing back out of the cell and also makes the glucose molecule more chemically reactive, allowing subsequent steps in glycolysis to effectively proceed.

The activity of hexokinase is critical because it not only initiates the glycolytic process but also ensures that glucose remains available for energy production within the cell. The subsequent reactions in glycolysis build upon this initial phosphorylation, ultimately leading to the generation of ATP and pyruvate. Each of the other enzymes listed plays important roles at different stages of glycolysis, but none initiate the process by phosphorylating glucose as hexokinase does.