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Question: How many oxygen molecules are involved in ETS if one molecule of Acetyl CoA is completely oxidised?...

How many oxygen molecules are involved in ETS if one molecule of Acetyl CoA is completely oxidised?

Explanation

Solution

We are well aware of the fact that glycolysis of 11 molecules of glucose generates two molecules of acetyl CoA for complete oxidation of one molecule of glucose six oxygen molecules are required.

Complete answer:
- We all know that in the presence of oxygen, further oxidation of pyruvate occurs in the matrix of mitochondria where it first oxidized into Acetyl CoA.
- The oxidation of pyruvate to acetyl enzymes involves the four oxidation-reduction steps occurring in citric acid cycle where the coenzyme A, NAD+NA{D^ + } and FADFAD are reduced to NADHNADH and FADH2FAD{H_2} respectively, oxygen is required here to reoxidised these coenzymes.
- Pyruvate dehydrogenase complex catalyses the transfer of acetyl group to coenzyme A resulting in formation of Acetyl-CoA. Participation of oxygen and sufficient ATP production takes place in two pathways: the electron transport chain and oxidative phosphorylation.
- In the presence of oxygen, when Acetyl CoA is produced, it enters the Krebs cycle and is oxidised to carbon dioxide and at the same time NAD is reduced to NADHNADH. This NADHNADH is now used in ETS to create ATP for oxidative phosphorylation.
- The electron transport system now transfers the electrons from NADHNADH and FADH2FAD{H_2} to the molecular oxygen which is finally reduced to form water molecules.
- So, to fully oxidise the one glucose molecule, two acetyl CoA molecules are metabolized by the Citric acid cycle and six molecules of oxygen are required for the complete oxidation of one glucose.
- Therefore we can say that for one molecule of Acetyl CoA, three molecules of oxygen will be required.

Hence the correct answer is 6 molecules of oxygen are involved in ETS if one molecules of Acetyl CoA is completely oxidized.

Note: 32 ATP molecules are generated for the complete oxidation of one molecule of glucose into carbon dioxide and oxidation of all the reduced coenzymes. ETS can be inhibited by the Cyanide ions that prevent transfer to electrons from cytochrome a3{a_3} to oxygen. Oligomycin inhibits the oxidative phosphorylation.