Question

Monosaccharides other than glucose can be modified to derivatives that can enter glycolysis. For each of the monosaccharides listed, indicate the derivative that enters glycolysis. The glycolytic pathway is given as a reference. The abbreviations DHAP and G3P represent dihydroxyacetone phosphate and glyceraldehyde‑3‑phosphate, respectively.

Answer 1

Answer: D-Fructose ---> fructose 6-phosphate or DHAP and G3P

D-Galactose ---> glucose 6-phosphate

D-Mannose ---> fructose 6-phosphate

(Note: The question is incomplete as it did not list of any monosaccharides)

Explanation:

In most organisms, hexoses other than glucose can undergo glycolysis after  being modified to derivatives that can enter glycolysis.

In the muscles and kidney, D-fructose is phosphorylated by hexokinase to fructose 6-phosphate which then enters glycolysis. In the liver, the liver enzyme fructokinase phosphorylates D-fructose to fructose 1-phosphate which is then cleaved to yield glyceraldehyde and DHAP. DHAP enters glycolysis while glyceraldehyde is phosphorylated by triose kinase to glyceraldehyde 3-phosphate which then enters glycolysis.

D-Galactose is phosphorylated by galactokinase to galactose 1-phosphate. The galactose 1-phosphate is then converted to glucose 1-phosphate by a series of reaction in which uridine diphosphate (UDP) functions as a coenzyme-like carrier of hexose groups. Glucose 1-phosphate is then converted by phoshoglucomutase to glucose 6-phosphate which then enters glycolysis.

D-mannose is phosphorylated by hexokinase to mannose 6-phosphate. Mannose 6-phosphate is then isomerized by phosphomannose isomerase to fructose 6-phoshate which then enters glycolysis.