Question

Oxidation of one molecule of glucose yields $38molecules$ of $ATP$ in the proportion of

• A. all the $38$ mols in mitochondrion
• B. $8$ outside mitochondria and $30$ inside mitochondrion
• C. two glycolysis and $36$ inside the Krebs' cycle
• D. two outside and $36$ inside the mitochondria.

Answer 1

Answer: (D)

The main outcome of aerobic respiration is cellular energy or ATP. This process is divided into two main components, one occurring in the cytoplasm, called glycolysis, and the other inside the mitochondria, called Kreb's cycle. Under the aerobic condition, the ATP formation from one molecule of glucose is, like:
During glycolysis:
1. 2 ATP are formed when 2 moles of 1,3-diphosphophoglycerate is converted to 2 moles of 3-PGA.
2. 2 ATP are formed when 2 moles of phosphoenol pyruvate is converted into PA.
3. 2 ATP are used in glycolysis in the first few steps.
Net gain of ATP in glycolysis is 4 - 2 = 2
4. 6 ATP are formed as 2 moles of NADH are sent to ETC which were formed when 2 moles of PGAL were converted to 2 moles of 1,3-diphosphoglycerate.
During oxidation of PA:
1. 6 ATP are formed as 2 moles of NADH are sent to ETC which were formed when 2 moles of PAs are converted 2 moles of acetyl CoA.
During TCA:
1. 2 ATP are formed directly when 2 moles of succinyl coA is converted into succinate.
2. 6 ATP is formed as 2 moles of NADH are sent to ETC which were formed when 2 moles of isocitrate are converted to 2 moles of oxalosuccinate.
3. 6 ATP is formed as 2 moles of NADH are sent to ETC which were formed when 2 moles of alpha-KG are converted to 2 moles of succinyl coA.
4. 4 ATP are formed when 2 moles of FAD are sent to ETC which were formed when 2 moles of succinate were converted to 2 moles of fumarate.
5. Finally, 6 ATP is formed as 2 moles of NADH are sent to ETC which were formed when 2 moles of malate is converted to 2 moles of oxaloacetate.
This means, from TCA and ETC, which occurs inside the mitochondria, and TCA, we get
6 + 6 + 6 + 6 + 6 + 4 + 2 = 36 ATPs
Thus, only 2 ATPs are formed outside the mitochondria, directly during glycolysis, the remaining 36 ATP are either formed in TCA (in mitochondria) or through ETC (in mitochondria).