Question

The direct gain of ATP from one mole of glucose during glycolysis by substrate-level phosphorylation is equal to
A. 4 ATP
B. 6 ATP
C. 36 ATP
D. 38 ATP

Answer 1

Hint: Glycolysis is an episode of reactions that remove glucose energy by separating it into two three-carbon molecules called pyruvates. Glycolysis occurs in the cytosol and thus can be split into two major parts: the energy-requiring phase and energy-releasing phase.

Complete answer: In the energy-requiring phase the starting glucose is reordered, and two groups of phosphates are bound to it. The phosphate groups make the transformed sugar now known as fructose-1,6-bisphosphate unstable, enabling it to be cut in two and to form two three-carbon phosphate-bearing sugar. But since phosphates used for these steps come via ATP, two ATP molecules are used. During the energy-releasing step, each three-carbon glucose is converted to another three-carbon molecule, pyruvate, through a series of events. Two ATP and one NADH molecules are produced in such reactions. Because this step actually occurs twice, once for each of the two three-carbon sugars, it makes four ATP and two NADH as a whole. Overall, glycolysis transforms one glucose six-carbon molecule to 2 pyruvate three-carbon molecules. The net products of such a process are two molecules of ATP (4 ATP produced-2 ATP used) and two molecules of NADH. If oxygen is present, the pyruvate can indeed be broken down all of the ways to carbon dioxide in cell respiration, culminating in several molecules of ATP.
So, the correct option is (A)

Note: Glycolysis is a metabolic process irrespective of oxygen. In certain species, glycolysis exists in the cytosol and is really a series of ten enzyme-catalyzed reactions. The glycolytic mechanism transforms one hexose (glucose) to two triose molecules (three-carbon carbohydrate) like pyruvate, and then a network of two ATP molecules (four formed, two consumed) and two NADH molecules.