Question

after step 5 in glycolysis can atoms from C 1 of the original glucose molecule distinguish from the C 6 of the original molecule that is where does the original C 1 end up after step 5 and where goes the original C 6 after step 5? Is it at the same place or different place

Answer 1

It is at the same place. In glycolysis, the fourth step is conversion of fructose 1,6-biphosphate (6 carbon molecules) into dihydroxyacetone phosphate (3 carbon molecules) and glyceraldehyde 3-phosphate (3 carbon molecules). Both these 3 carbon molecules are interconvertible with the help of enzyme triose phosphate isomerase. After 4th step only glyceraldehyde 3- phosphate continues in the glycolytic pathway. As a result, all of the dihydroxyacetone phosphate molecules produced are further acted on by the enzyme triphoshpate isomerase, which converts dihydroxyacetone phosphates into glyceraldehyde 3-phosphate so it can continue in glycolysis. In 5th step of glycolysis all the glyceraldehyde 3-phosphate molecules converted into 1,3-biphosphoglycerate with the help of enzyme glyceraldehyde phosphate dehydrogenase. Thus, after step 5, C1 or C2 both ends up in the same product that is 1, 3 biphosphoglycerate.