Question

Glycolysis: Hexokinase ΔG′°= −16.7 kJ/mol Dephosphorylation of glucose 6-phosphate. Enzyme: Glucose 6-phosphatase glucose 6-phosphate + H2O -> glucose + Pi ΔG'°= −13.8 kJ/mol Water hydrolysis reaction. Now liver cell has glucose to export.

Answer 1

The enzyme hexokinase initiates glycolysis by phosphorylating glucose to form glucose-6-phosphate (G-6-P), trapping glucose inside the cell and preparing it for further metabolism. The reaction is tightly regulated by the product G-6-P and the availability of glucose in the cell.

Step-by-step explanation:

Glycolysis and Hexokinase Function

The process of glycolysis begins in the cytoplasm of cells where glucose, a six-carbon sugar, enters the pathway. The first reaction of glycolysis is catalyzed by the enzyme hexokinase. This enzyme is crucial as it phosphorylates glucose to form glucose-6-phosphate (G-6-P), which is an irreversible step. One molecule of ATP is required for this phosphorylation, which effectively traps the glucose within the cell due to the added negative charge, preventing its efflux back into the bloodstream.

Interestingly, the enzyme's activity can be regulated by its product, glucose-6-phosphate, suggesting a feedback inhibition mechanism to prevent overaccumulation of G-6-P. In the liver, a similar enzyme called glucokinase can perform the same function when glucose levels are abundant.

In a subsequent set of reactions, G-6-P is isomerized to fructose-6-phosphate and further metabolized through glycolysis, ultimately producing pyruvate and ATP. The initial investment of ATP in the hexokinase reaction is offset by the generation of a larger number of ATP molecules as glycolysis proceeds.