Question

An important feature of the regulation of glucose catabolism via glycolysis and the pentose pathway is reflected in the observation that:

A. transaldolase and transketolase are isomers of fructose-1,6-diphosphate aldolase and pyruvate ketolase, respectively.

B. regulation is primarily achieved by segregation of glucose catabolism via the glycolytic pathway in the cytosol and the pentose pathway in the mitochondria.

C. unlike the glycolytic pathway, the pentose pathway is activated uniquely by high levels of NADPH.

D. the catabolism of glucose via the pentose pathway can be equal to or greater than glucose catabolism via the glycolytic pathway in cells that are carrying out biosynthetic reactions involving production of fatty acids, steroids and nucleotides.

Which answer choice is correct? Could you please explain why the answer choice is correct and why the other ones are wrong? Thank you

Answer 1

D. the catabolism of glucose via the pentose pathway can be equal to or greater than glucose catabolism via the glycolytic pathway in cells that are carrying out biosynthetic reactions involving production of fatty acids, steroids and nucleotides.

Catabolism of glucose via the pentose phosphate pathway (PPP) generates NADPH (required for the synthesis of fatty acids & steroids) and ribose-5-phosphate (required for the synthesis of nucleotides).

So, in a cell that carries out biosynthesis of fatty acids & nucleotides, NADPH and ribose-5-phosphate (via PPP) are in demand. Hence, PPP is equal to or higher than glycolysis in these cells.