Question

When one glucose molecule enters the glycolytic pathway, two molecules of pyruvate are created. This change in stoichiometry is ultimately due to the actions of:

A. hexokinase, which phosphorylates the glucose molecule.

B. phosphofructokinase-1, which creates a doubly-phosphorylated fructose molecule.

C. aldolase, which cleaves the doubly-phosphorylated fructose molecule into two different 3-carbon molecules.

D. triose phosphate isomerase, which catalyzes the rearrangement of bonds within one dihydroxyacetone phosphate molecule.

E. phosphoglycerate kinase, which dephosphorylates two molecules of 1,3-bisphosphoglycerate.

Answer 1

Solution:

A.hexokinase,which phosphorylates the glucose molecule

Hexokinase Traps Glucose in the Cell and Begins Glycolysis

Glucose enters cells through specific transport proteins and has one principal fate: it is phosphorylated by ATP to form glucose 6-phosphate. This step is notable for two reasons:

(1) glucose 6-phosphate cannot diffuse through the membrane, because of its negative charges, and (2) the addition of the phosphoryl group begins to destabilize glucose, thus facilitating its further metabolism. The transfer of the phosphoryl group from ATP to the hydroxyl group on carbon 6 of glucose is catalyzed by hexokinase.