Question

Skeletal muscle contracting under anaerobic conditions further metabolize the pyruvate produced by glycolysis to lactic acid as part of a fermentation reaction.Why is this reaction essential for the anaerobically functioning cell?

Answer 1

Anaerobic glycolysis is the transformation of glucose to lactate when limited amounts of oxygen (O₂) are available.

• Anaerobic glycolysis is only an effective means of energy production during short, intense exercise, providing energy for a period ranging from 10 seconds to 2 minutes.
• The anaerobic glycolysis (lactic acid) system is dominant from about 10–30 seconds during a maximal effort. It replenishes very quickly over this period and produces 2 ATP molecules per glucose molecule or about 5% of glucose's energy potential (38 ATP molecules). The speed at which ATP is produced is about 100 times that of oxidative phosphorylation.
• Anaerobic glycolysis is thought to have been the primary means of energy production in earlier organisms before oxygen was at high concentration in the atmosphere and thus would represent a more ancient form of energy production in cells.

This reaction essential for the anaerobically functioning cell because

In mammals, lactate can be transformed by the liver back into glucose.

Fates of pyruvate under anaerobic conditions:

1.     Pyruvate is the terminal electron acceptor in lactic acid fermentation
When sufficient oxygen is not present in the muscle cells for further oxidation of pyruvate and NADH produced in glycolysis, NAD+ is regenerated from NADH by reduction of pyruvate to lactate. Pyruvate is converted to lactate by the enzyme lactate dehydrogenase. The standard free energy change of the reaction is -25.1 kJ/mol.