Glycolysis - Medical Science

Q1:

Glucose from the breakdown of glycogen is obtained in

A the liver by phosphorolysis

B the muscles by phosphorolysis

C the muscles by hydrolysis

D both (a) and (b)

ANS:D - both (a) and (b)

Muscle which contains only hexokinase can use this enzyme to phosphorylate fructose producing F6P which is a direct glycolytic intermediate. In liver the glucokinase, is specific for glucose as a substrate, therefore it requires an alternative enzyme to phosphorylate fructose. Hepatic fructokinase can phosphorylate fructose on C-1 to produce fructose-1-phosphate (F1P).

Instead of F 1,6 biphosphate aldolase , the liver containing aldolase B that can use F1P as a substrate to generate dihdroxyacetone phosphate( DHAP) and glyceraldehyde. The DHAP is converted, by triose phosphate isomerase(TIM), to G3P while the glyceraldehyde is phosphorylated to G3P by triose kinase.