Answer to Question #168020 in Biochemistry for Yashika Sharma

Question

Cell in culture are fed glucose molecules labled with 14C at carbon 2. Trace the radioactive label through one pass through the pentose phosphate pathway?

Answer 1

This labeled atom 14C at carbon 2 will be part of all stages (all of the products) of the pentose phosphate pathway.

Oxidative phase: glucose-6-phosphate into 6-phosphoglucono-δ-lactone; 6-phosphoglucono-δ-lactone into  6-phosphogluconate;  6-phosphogluconate into ribulose 5-phosphate

Non-oxidative phase: ribulose 5-phosphate into ribose 5-phosphate; ribulose 5-phosphate into xylulose 5-phosphate; xylulose 5-phosphate +ribose 5-phosphate into glyceraldehyde 3-phosphate + sedoheptulose 7-phosphate; sedoheptulose 7-phosphate + glyceraldehyde 3-phosphate into erythrose 4-phosphate + fructose 6-phosphate; xylulose 5-phosphate + erythrose 4-phosphate into glyceraldehyde 3-phosphate + fructose 6-phosphate.

The scheme could be seen in the picture below.