The upcoming discussion will update you about the similarities and differences between anaerobic respiration and fermentation.
Anaerobic respiration is often considered synonymous with fermentation. Anaerobic respiration is also called intra-molecular respiration.
Here the carbohydrates are degraded into two or more simpler molecules by processes not requiring molecular oxygen.
In anaerobic respiration (fermentation) the carbon-skeleton of glucose molecule is never completely released as CO2 and in some it may not appear at all. It does not require mitochondria and is completed in cytoplasm i.e., all enzymes of anaerobic respiration are present in cytoplasm.
The reason for believing that the two processes fermentation and anaerobic respiration are identical (in-fact synonymous) are:
1. Hexose sugars are respiratory substrate in both processes.
2. The principal end products are same (CO2 and C2H5OH) in both the cases.
3. The wide spread occurrence (probably universal) of the enzyme zymase complex in all the tissues of higher plants.
4. Pyruvic acid and acetaldehyde are formed as intermediates in both the processes.
5. Inorganic phosphate enhances the rate of sugar breakdown in both.
Although, biochemically speaking anaerobic respiration and fermentation are identical (or synonymous) but by convention the:
(1) Anaerobic respiration taking place in microorganisms (yeast, bacteria etc.) is usually called fermentation,
(2) Also fermentation is usually mentioned as anaerobic respiration with effervescence (as in many cases fermentation takes place in substrate in solution form and CO2 is released as bubbles),
(3) Also anaerobic respiration takes place inside the cells but fermentation may take place outside the cells by extracellular enzymes.