Question

Some explanations of glycolysis, lactic acid fermentation and aerobic cellular respiration seem to indicate that your cells SWITCH between the two options to finish glycolysis: lactic acid fermentation OR cellular respiration. This is not the case! Your cells do not choose EITHER lactic acid fermentation OR aerobic cellular respiration.

What is the necessary item for glycolysis to continue to aerobic cellular respiration instead of lactic acid fermentation? Unless you are dead (no respiration, no blood circulation), are your muscle cells getting some of this? Explain.

Therefore, a better explanation might be: “If a cell is only getting 75% as much O2 as it needs to make enough ATP through aerobic cellular respiration, then (what %?) of the pyruvates from glycolysis will go into the mitochondria.”

In the above situation, what will happen to glycolysis rates that move forward to lactic acid fermentation? Why?

Answer 1

Glycolysis is always occurring in an individual. Its final products differ in presence and absence of oxygen.

In presence of oxygen – Cellular respiration occur and pyruvate and the electron carrier NADH are formed.

In absence of oxygen – fermentation occur and electrons from NADH molecules are removed and NAD+ molecules are recycled. Fermentation does not make ATP and lactic acid is produced.

If only 75% of the required oxygen is present then pyruvate molecule requiring nearly 25% of oxygen will be converted into lactate. In case if 100% oxygen is present, all pyruvates molecules will be transported into the mitochondrial matrix.