Question

Compare the atp yield of three glucose molecules that enter glycolysis and are converted to pyruvate with that of three glucose molecules that proceed through the pentose phosphate pathway such that their carbon skeletons (as two f6p and one gap) reenter glycolysis and are metabolized to pyruvate

Answer 1

Glycolysis refers to the metabolic procedure of transforming one molecule of glucose into two molecules of pyruvate via an arrangement of ten enzymatic catalyzed reactions.  

Glucose + 2ADP + 2NAD+ + 2Pi -> 2 pyruvate + 2ATP + 2NADH + 2H+ + 2H2O

In this, from three molecules of glucose six molecules of ATPs are generated.  

On the other hand, the pentose phosphate pathway can take place to metabolize dietary pentose sugars obtained due to the digestion of nucleic acids as well as to reorganize the carbon skeletons of dietary carbohydrates into gluconeogenic/glycolytic intermediates (F6P and GAP).  

The pentose phosphate pathway is a prime producer of NADPH for the production of fatty acids. This pathway is not created to generate ATP.