Which of the following metabolic conversions involved in glucose synthesis requires the direct expenditure of ATP?

a. 3-Phosphoglycerate - -> 1,3-bisphosphoglycerate

b. Glyceraldehyde-3-phosphate + dihydroxyacetone phosphate - -> fructose-1,6-bisphosphate

c. Fructose-1,6-bisphosphate - -> fructose-6-phosphate

d. 1,3-Bisphosphoglycerate - -> glyceraldehyde-3-phosphate

3-Phosphoglycerate - -> 1,3-biphosphoglycerate

Explanation:

The reaction of 3-Phosphoglycerate - -> 1,3-biphosphoglycerate is one of the ten reactions involved in the biosynthesis of glucose, a process also known as gluconeogenesis. This reaction involves the participation of the enzyme Phosphoglycerate kinase, which catalyzes the transfer of one of the phosphate groups from the ATP to the 3-Phosphoglycerate in order to form 1,3-biphosphoglycerate. This then results in an endergonic reaction, as it requires energy for it to occur, and in this case, that energy comes from the ATP molecule, which by losing a phosphate group then becomes an ADP molecule.