To solve this problem, we need to identify the enzyme that catalyzes the conversion of glucose to glucose-6-phosphate, which is the first irreversible reaction of glycolysis.$\newline \bullet$Glycolysis is the metabolic pathway that converts glucose into pyruvate, releasing energy and forming ATP and NADH.$\newline \bullet$The first step of glycolysis involves the phosphorylation of glucose to form glucose-6-phosphate.$\newline \bullet$This reaction is catalyzed by the enzyme hexokinase.$\newline \bullet$Hexokinase transfers a phosphate group from ATP to glucose, forming glucose-6-phosphate and ADP.$\newline$Therefore, the enzyme responsible for this reaction is hexokinase.$\newline$Thus, the correct option is Option 2: Hexokinase.