Question

Which molecule(s) provide high energy electrons to the electron transport chain in oxidative phosphorylation?

	a.	ATP
	b.	NADH
	c.	FADH2
	d.	a and b
	e.	b and c

For every molecule of pyruvate oxidized in aerobic cellular respiration ____________ is(are) produced.

	a.	one ethanol and one CO2 molecule
	b.	one acetyl CoA molecule
	c.	one acetyl CoA and one CO2 molecule
	d.	three ATP molecules

Answer 1

Ans.1

The answer is (e) b and C.

Explanation:

Oxidative phosphorylation is the process of synthesis of ATP by phosphorylation of ADP, which takes place in the mitochondria during the aerobic respiration process.The energy that is required for the phosphorylation of ADP is obtained by the electron transport chain.This is done by the electron carriers NADH and FADH2 that was produced from the other steps of the cellular respiration. They transfer their electrons to the molecules near the starting of the transport chain and turn back into NAD+ and FAD, which in the later steps of cellular respiration is reused. In a redox reaction, the electrons of NADH are at high energy levels and thus NADH can directly transfer the electrons to complex-I, turning back into NAD+ .Whereas, since the electrons of FADH2 are at low energy levels, it cannot directly transfer the electrons to complex-I and instead transfer it to the transport chain through complex-II and turns back into FAD.

Thus, NADH and FADH2  provide high energy electrons to the electron transport chain in oxidative phosphorylation and hence the answer.

Ans.2:

The answer is (c) one acetyl CoA molecule and one CO2 molecule

Explanation:

In aerobic respiration, the pyruvate molecules that is formed at the end of glycolysis are transported into the mitochondria inorder to enter into the next pathway of respiration.But for that it must first undergo some changes,that is oxidation of pyruvate must happen in the mitochondria before it can enter the next pathway.In the mitochondria these pyruvate first transforms into a 2 carbon acetyl group by removing a carboxyl group and releasing releasing a molecule of CO2 into the surrounding.This step also produces NADH.This acetyl group is then picked up by coenzyme A or CoA,a carrier compound,resulting in the formation of acetyl CoA.

Thus for every molecule of pyruvate oxidized , one molecule of acetyl CoA and one molecule of CO2 is produced and hence the answer.