Question

1)Assume that fructose is metabolized in the liver.  How many ATP are formed from the complete oxidation of sucrose in the liver? Show your calculations

2) If the carbonyl carbon in oxaloacetate (in the muscle) are labeled with ¹⁴C, where in glucose did the label originate?

a.     Carbon #3

b.     Carbon #2

c.     Carbon #1

d.     Glucose was not labeled

e.     Not enough information is given to answer this question

Answer 1

1. Sucrose is a disaccharide of two monosaccharides: glucose and fructose. Each glucose can yield 36–38 ATP through glycolysis, Krebs (TCA) and electron transport chain. Fructose enters later in glycolysis and can yield upto 28-30 ATP. Thus, complete oxidation of sucrose will yield 64-68 ATPs.

2. The correct answer is option (B): Carbon #2. Because this C2 from glucose is converted to pyurvate and then Acetyl CoA which then becomes the carbonyl group of oxaloacetate.