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.