Anaerobic Respiration

Overview of Anaerobic Respiration

  • Anaerobic respiration refers to the process where energy is released from glucose without oxygen.
  • It occurs in various microbial and plant cells and is common in animal muscles during vigorous exercise.
  • Products of anaerobic respiration include lactate in animals (lactic acid fermentation) or ethanol and carbon dioxide in plants and yeast (alcoholic fermentation).

Process of Anaerobic Respiration

  • The first stage of anaerobic respiration is same as aerobic one: glycolysis.
  • In glycolysis, one molecule of glucose is broken down into two molecules of pyruvate, 2 ATP molecules are generated, and NAD+ is reduced to NADH.
  • In absence of oxygen, the process diverts from aerobic respiration and NADH is reoxidised to NAD+ by reducing pyruvate.

In Animal Cells

  • In muscle cells, reoxidised NAD+ cycles back into glycolysis, allowing continuous ATP production.
  • Pyruvate is converted into lactate, a process that regenerates NAD+.
  • If lactate builds up, it can cause muscle fatigue. It is transported to the liver to be oxidised back to pyruvate when oxygen becomes available.

In Plant Cells and Yeast

  • Pyruvate is converted to carbon dioxide and ethanol, also regenerating NAD+ in the process.
  • The process is vital in baking and brewing, where the carbon dioxide causes dough to rise and the ethanol gives alcohol its characteristic intoxicating effect.

Anaerobic Respiration Yield

  • Anaerobic respiration is far less efficient than aerobic respiration.
  • It yields only 2 ATP molecules per glucose molecule, compared to around 32 ATP molecules yielded by aerobic respiration.

Importance of Anaerobic Respiration

  • Despite its low energy yield, anaerobic respiration is essential as it allows continued ATP production when oxygen is scarce.
  • It’s a survival mechanism for organisms in oxygen-poor environments, and for muscles during heavy exercise when oxygen delivery is limited.
  • Also, it happens quickly, providing a burst of energy much faster than aerobic respiration can.