Question

During the complete oxidation of glucose, the proportion of ATP formed by substrate-level phosphorylation is ______.

• A. 100%
• B. 89.5%
• C. 10.5%
• D. 50%

Answer 1

Answer: (C)

Respiration is the process or mechanism to break down food molecules to release energy in the form of ATP. During the process of aerobic respiration, phosphorylation of ADP occurs forming the energy currency molecule - Adenosine triphosphate. The energy required for the production of proton gradient which is needed for phosphorylation is obtained from the oxidation-reduction of the molecules. One of the steps of the respiration process is glycolysis where 6C-glucose is broken down to 3C-pyruvate.
In the first step of aerobic respiration, glycolysis takes place where the glucose molecule is broken down into two molecules of 3C-pyruvic acids. Each of these pyruvates enters the next phase, that is the Kreb's cycle. In each round of the TCA cycle, three molecules of $NAD{H}_2$ , one GTP, and one molecule of $FAD{H}_2$ are generated using 1 Acetyl CoA. Thus, for each glucose molecule in a total of 6 molecules of NADH2, 2GTP's and 2 molecules of $FAD{H}_2$ are formed in 2 turns of Kreb's cycle.
Aerobic respiration results in formation of 38 ATPs of which 4 ATPs are produced in glycolysis which is approximately 10.5%.