Question

The enzyme Sucrase hydrolyzes sucrose into its two component sugars. Draw the entire pathway for the conversion of sucrose to pyruvate in the LIVER. Both of the component sugars of sucrose are labeled with 14C at positions 1 and 5. Show where the 14C labels would be found in the pyruvate that is produced. You must give the name of every enzyme and metabolite as well as draw the structure for each metabolite. Glyceraldehyde is produced as a metabolite in the pathway. There are two possible pathways for glyceraldehyde to continue down glycolysis to pyruvate; you must draw BOTH pathways. You do not have to draw the structures of any cofactors ( ATP, NAD etc) but you must include them in all of the appropriate reactions.

Answer 1

Sucrose is a polysaccharide that contains multiple molecules of carbohydrates (glucose and fructose) that are joined by gycosidic bonds.

The body cannot absorb complex polysaccharides directly. Hence sucrose is digested (hydrolysed) into simpler molecules glucose and fructose, which are monosaccharides.

Sucrose digestion begins in small intestines. Small intestines secrete the digestive enzyme sucrase.

Sucrase catalyzes the hydrolysis of sucrose into glucose and fructose.

Thus produces monosaccharides (glucose and fructose) are carried through blood stream to the liver where they are further processed.

Glocose is converterd to pyruvate through the process called glycolysis, while metabolism of fructose occurs through the process called fructolysis.

Fructolysis is a more complex pathway than glycolysis. Glycolysis occurs in almost all the tissues but fructolysis occurs primarily in the liver.