Question

Describe how muscles produce energy when oxygen is not present using lactic acid fermentation.

Answer 1

• In absence of oxygen, muscle cells produce energy by anaerobic respiration.
• Anaerobic respiration steps - glycolysis and fermentation.

Glycolysis :-
• This is common step for both aerobic and anaerobic respiration.
• It occurs in cytoplasm and in this step one molecule of glucose is converted into two molecules of pyruvate.
• Total 4 ATPs produced and 2 ATPs used in this process, so net 2 ATPs are produced by glycolysis.
• 2 NADH also produced.

Fermentation/ Lactic acid fermentation :-
• In this process, pyruvate is converted to lactate or lactic acid.
• There is no ATP is produced in this process.
• In this process, NAD+ is produced from NADH, this NAD+ is reused in glycolysis. This is the only significance of this process that it regenerates NAD+ for glycolysis.

Hence, muscle cells produce 2 ATP per glucose molecule in absence of oxygen.