Question

You see your friend eating pancakes with maple syrup. Maple syrup is primarily sucrose Calculate the total amount of ATP generated from the complete aerobic oxidation - that is, all the way through the ETC - of one sucrose molecule. (Assume that the fructose enters catabolism as fructose 6-phosphate, and that the malate-aspartate shuttle is employed.) Hint: First, count up all the ATP/GTP, NADH, and FADH2 produced. Then, convert and calculate everything at the end.

Show work and explain each step.************************

Answer 1

Sucrose is made up of glucose and a fructose molecule.

The oxidation of that 1 glucose through the glycolysis and Krebs-cycle produces 36 or 38 molecules of ATP. 36 ATP is produced if the 2 NADH molecules produced in the glycolysis enter the mitochondria by the maleic acid-fumarate pathway, 38 ATP is produced if that 2 NADH molecules enter the mitochondria via the malate-aspartate shuttle.

The fructose can be broken down in the ways:

$ With the hexokinase enzyme, it could be transformed into fructose-6-phosphate, which can participate in the glycolysis, producing the same amount of ATP like a glucose molecule.

$ The fructokinase enzyme transforms it into fructose-1-phosphate (1 ATP is used), which is broken down via the aldolase B enzyme into glycerin and glyceraldehyde-3-phosphate or dihydroxyacetone-phosphate. The glycerin is transformed into glyceraldehyde-3-phosphate using 1 ATP molecule. So with these steps 36–38 ATP is made.

But in the question, it's clearly mentioned about first way.

so energy yield per molecule of sucrose is now equal to 2 molecules of glucose energy when its completely oxidized through glycolysis plus Krebs cycle, under aerobic condition.

in glycolysis

      2 ATP losed +2 NADH +2 ATP =8 ATP

KREBS CYCLE

2 (1 ATP+4 NADH +1 FADH2+ 1GTP) = 30 ATP

TOTAL 38 ATP

(1 NADH = 3 ATP, 1 FADH2 =2 ATP CRITERIA TAKEN)

SO FOR 2 MOLECULES GIVES 38+38 =76 ATP

FOR 1 MOLECULE OF SUCROSE YEILD = 76 ATP.