Anaerobic Respiration

Anaerobic Respiration: The Basics

• Anaerobic respiration refers to the process of generating energy from nutrients without the use of oxygen.
• This form of respiration typically occurs in microorganisms but also happens in the muscle cells of animals during high-intensity exercise when oxygen supply is inadequate.
• The word ‘anaerobic’ means ‘without air’, specifically without oxygen.

The Process of Anaerobic Respiration

• Anaerobic respiration starts with glycolysis, in which one glucose molecule splits into two pyruvate molecules, generating a small amount of energy.
• In the absence of oxygen, the pyruvate undergoes fermentation. The exact process and products of fermentation vary depending on the organism.
• In animal cells, the pyruvate is converted into lactate, in a process known as lactic acid fermentation. This also regenerates NAD+ from NADH, allowing glycolysis to continue.
• This process can cause a build-up of lactic acid in muscles, leading to cramp.
• In yeast and some bacteria, the pyruvate is converted into ethanol and carbon dioxide, in a process known as alcohol fermentation.

Energy Yield of Anaerobic Respiration

• Anaerobic respiration is less efficient than its counterpart, aerobic respiration.
• For every glucose molecule broken down during anaerobic respiration, only 2 ATP molecules are produced. Aerobic respiration, on the other hand, can yield up to 38 ATP molecules from the same glucose molecule.

Importance of Anaerobic Respiration

• Despite being less efficient, anaerobic respiration provides a rapid burst of ATP energy for muscular activity.
• It allows organisms to survive in conditions where oxygen is scarce or absent.
• Anaerobic respiration in yeast is exploited in the baking and brewing industries, for producing bread and alcoholic drinks respectively.