WHICH ENZYME CATALYZES THE CONVERSION OF GLUCOSE TO GLUCOSE-6-PHOSPHATE IN GLYCOLYSIS?

• a) Hexokinase ✓
• b) Phosphofructokinase
• c) Pyruvate kinase
• d) Aldolase

In glycolysis, the conversion of glucose to glucose-6-phosphate is a crucial step that initiates the metabolic pathway for glucose breakdown. This reaction is catalyzed by an enzyme known as hexokinase.

Step-by-Step Explanation:

1. Glycolysis Overview: Glycolysis is a series of enzymatic reactions that convert glucose into pyruvate, producing ATP and NADH in the process. It occurs in the cytoplasm of cells and consists of ten steps.
2. First Step of Glycolysis: The first step in glycolysis involves the phosphorylation of glucose. This reaction is essential because it traps glucose within the cell and prepares it for further metabolism.
3. Role of Hexokinase: Hexokinase is the enzyme responsible for this phosphorylation reaction. It catalyzes the transfer of a phosphate group from ATP (adenosine triphosphate) to glucose, resulting in the formation of glucose-6-phosphate.
4. Mechanism: The mechanism involves hexokinase binding to both glucose and ATP, facilitating the transfer of a phosphate group from ATP to the hydroxyl group on carbon 6 of glucose. The overall reaction can be summarized as: Glucose + ATP → Glucose-6-phosphate + ADP
5. Importance of Glucose-6-Phosphate: The formation of glucose-6-phosphate serves multiple purposes:
   • It prevents glucose from leaving the cell since phosphorylated sugars cannot easily cross cell membranes.
   • It acts as a substrate for further reactions in glycolysis or can enter other metabolic pathways such as glycogenesis or pentose phosphate pathway.
6. Other Enzymes Listed:
   • Phosphofructokinase (PFK): This enzyme catalyzes a later step in glycolysis, specifically converting fructose-6-phosphate to fructose-1,6-bisphosphate.
   • Pyruvate Kinase: This enzyme catalyzes one of the final steps in glycolysis, converting phosphoenolpyruvate (PEP) to pyruvate while generating ATP.
   • Aldolase: This enzyme catalyzes a different reaction where fructose-1,6-bisphosphate is split into two three-carbon molecules.

Given this detailed analysis, we can conclude that:

The correct answer is: a) Hexokinase