anaerobic respiration

When the body is in oxygen debt, there is no available final electron acceptor and so the electron transport chain ceases to work. As a result, the Krebs Cycle and Link Reaction also stop functioning because there is no need to keep reducing NAD that will not be able to be used.

As a result, what ends up happening is:

1) Glucose enters the cell and undergoes glycolysis, as it would usually do. This is because glycolysis is an anaerobic process and does not require oxygen.
2) This produces 2 pyruvate molecules, 2 net ATP molecules and 2 reduced NAD molecules.
3) The reduced NAD molecules cannot go to the electron transport chain (because there is no oxygen), so they must be recycled.
4) Pyruvate accepts the hydrogen from the reduced NAD molecules, so that they can now go and be used in more glycolysis.
5) When it accepts the hydrogen, with the assistance of lactate dehydrogenase, you have the formation of lactate.

This lactate is then carried to the liver, where it is broken down. Too much anaerobic respiration will lead to an influx of lactate in the cell, which you do not want because it will lower the pH of the cell and thus affect enzyme-controlled reactions within the cell; this leads to a condition called muscle fatigue.

does lactate dehydrogenase also convert lactate back to pyruvate?

Yeah

Can someone explain to me how anaerobic respiration work to produce lactic acid? cori cycle?

When the body is in oxygen debt, there is no available final electron acceptor and so the electron transport chain ceases to work. As a result, the Krebs Cycle and Link Reaction also stop functioning because there is no need to keep reducing NAD that will not be able to be used.

As a result, what ends up happening is:

1) Glucose enters the cell and undergoes glycolysis, as it would usually do. This is because glycolysis is an anaerobic process and does not require oxygen.
2) This produces 2 pyruvate molecules, 2 net ATP molecules and 2 reduced NAD molecules.
3) The reduced NAD molecules cannot go to the electron transport chain (because there is no oxygen), so they must be recycled.
4) Pyruvate accepts the hydrogen from the reduced NAD molecules, so that they can now go and be used in more glycolysis.
5) When it accepts the hydrogen, with the assistance of lactate dehydrogenase, you have the formation of lactate.

This lactate is then carried to the liver, where it is broken down. Too much anaerobic respiration will lead to an influx of lactate in the cell, which you do not want because it will lower the pH of the cell and thus affect enzyme-controlled reactions within the cell; this leads to a condition called muscle fatigue.

It is not lactate which lowers the pH of the cell. Lactate is the deprotonated form of lactic acid and lactic acid is NOT produced by the body. The hydrolysis of ATP, which is needed to release energy for muscle contraction, releases protons. Under normal aerobic conditions, the electron transport chain reincorporates these protons when producing more ATP. However, under anaerobic conditons, there is not sufficient ATP production (since the ETC produces the bulk of the ATP, and the ETC ceases to work) and as such, these protons are not reincorporated into ATP at a sufficient rate and as such, accumulate in the cells in the blood causing lactic acidosis - acidosis characterised by high lactate levels. This is something which used to confuse me. As stated, in acidic environments, the enzymes involved in glycolysis (which is the only metabolic pathway which can function in anaerobic conditions) are inhibited and so strenuous levels of exercise can only be sustained for a few minutes at best. You can kind of think of this as a defence mechanism, the levels of acid increase until even anaerobic respiration stops which forces your muscles to stop contracting and so force a recovery period - preventing serious damage to the muscles.

Without oxygen to act as the final electron acceptor in the electron transport chain, the electron transport chain can no longer proceed and so NADH and FADH₂ can no longer be oxidised to NAD⁺ and FAD respectively. As such, the Link reaction and the Krebs cycle can no longer occur since they require NAD⁺ and FAD. However, glycolysis is the metabolic pathway which can still function as it can reduce pyruvate to lactate (by donating a hydride ion, H^-, from the NADH and an H⁺ ion to pyruvate) and in doing so oxidises NADH back to NAD⁺ - allowing glycolysis and hence a small but steady production of ATP to continue.

The production of lactate induces this, though? That is what I was trying to say.

Apologies, though, my bad


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