Final answer:
In gluconeogenesis, hexokinase is replaced by glucose-6-phosphatase to reverse the glycolysis process and produce glucose from non-carbohydrate sources, mainly occurring in the liver and kidneys.
Step-by-step explanation:
In gluconeogenesis, the enzyme hexokinase is replaced by glucose-6-phosphatase. Hexokinase is responsible for phosphorylating glucose to glucose-6-phosphate in glycolysis, using ATP as the source of the phosphate. This reaction is reversible in gluconeogenesis through the action of glucose-6-phosphatase. Unlike glycolysis, which occurs in many tissues, glucose-6-phosphatase is found mainly in the liver and kidney and contributes to the process of endogenous glucose production from non-carbohydrate sources, particularly during fasting or prolonged exercise.