Question

How many moles of glucose are required if all of the glucose first proceeds through the pentose phosphate pathway before proceeding through the rest of glycolysis on its way to pyruvate?

Answer 1

We know that one molecule of glucose when oxidized it gives two molecules of acetyl CoA

So if any process requires "n" carbon atom molecule then number of acetyl coA required = n/2

Therefore number of glucose molecule required will be = n/4

If all the glucose goes through pentose phosphate pathway before proceeding through rest of glycolysis then

a) In each pentose phosphate pathway : number of glucose molecules needed are "3"

b) In the pathway there will be one decarboxylation (removal of CO2) in each step which will cause loss of total three carbon atoms from three glucose molecules

c) the pathway finally gives : (i) one molecule of glyceraldehyde-3-phosphate (ii) two molecules of fructose phosphate

d) one molecule of fructose phosphate gives two acetyl CoA molecule (similar to glucose), in all four acetyl CoA from two molecules of fructose phosphate

e) glyceraldehyde-3-phosphate will give one molecule of acetyl CoA

f) so we can say that three glucose molecules will give five acetyl CoA molecules

g) as we need n/2 molecules of Acetyl CoA for a molecule with n number of carbon atoms so the number of glucsoe molecules required will be = 0.3 X n molecules