Question

When would a cell favor anerobic metabolism over aerobic metabolism? Which of the metabolic pathways are utilized when this is the case? How is NADH regenerated?

Answer 1

The cell favours anaerobic respiration over aerobic respiration when there is a absence or shortage of oxygen during heavy muscular activities etc. When the lungs cannot put enough oxygen in the blood to meet the demand of muscles. Glycolysis is the first step of both aerobic and anaerobic respiration which does not require oxygen. Pyruvate is reduced to lactic acid by NADH which becomes NAD+ in the presence of enzyme lactate dehydrogenase.Thus NAD+ is regenerated in this process which was used in glycolysis. It is also known as fermentation process. The end products are lactic acid or ethanol and ATP molecules. Less ATP molecules are produced in anaerobic respiration as compared to aerobic. Hence it is less efficient process.