Question

why is there a net yield of two, not four, atp molecules in glycolysis?
a) 2 molecules of atp are produced from atp synthase.
b) 2 molecules of atp are used to begin glycolysis.
c) 2 molecules of atp are used to complete glycolysis.
d) 2 molecules of atp are produced during glycolysis.

Explanation:

Glycolysis is the metabolic pathway that converts glucose into pyruvate. In the first stage of glycolysis, 2 molecules of ATP are used (for phosphorylation reactions, like the conversion of glucose to glucose - 6 - phosphate and fructose - 6 - phosphate to fructose - 1,6 - bisphosphate). In the second stage, 4 molecules of ATP are produced (through substrate - level phosphorylation, for example, the conversion of 1,3 - bisphosphoglycerate to 3 - phosphoglycerate and phosphoenolpyruvate to pyruvate). The net yield is calculated as the number of ATP produced minus the number of ATP used. So, net ATP = 4 (produced) - 2 (used)=2.

Answer:

B. 2 molecules of ATP are used to begin glycolysis.