Cell Metabolism - Stages of glucose oxidation: glycolysis, krebs cycle and oxidative phorphorylation

4 important questions on Cell Metabolism - Stages of glucose oxidation: glycolysis, krebs cycle and oxidative phorphorylation

Is there oxygen consumed in the Krebs cycle or the linking step?

No there is no oxygen consumed so far.

Can cells also metabolize other monosaccharides? If yes, how do they do it?

Yes they can. To use these sugars, cells first convert them into certain intermediates of glycolysis. These intermediates are then fed into the glycolysis pathway and oxidized in the usual manner.

What happens when there is not enough oxygen available to accept electrons in the electron transport chain?

The flow of electrons slows, creating a "traffic jam". This causes the co-enzyme molecules to become trapped in their reduced forms, and levels of the co-enzyme NAD+ decrease. A supply of NAD+ is necessary for proper operation of the glycolysis pathway and the Krebs cycle and a shortage slows all ATP-producing steps and can lead to exhaustion of the ATP supply.
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How is exhaustion of the ATP supply caused by oxygen shortage solved?

The enzyme lactate dehydrogenase (LDH) can convert pyruvate to lactate and in the process convert NADH + H+ to NAD+. This free NAD+ can then ensure that the glycolysis can continue.

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