The energy releasing metabolic process in which substrate is oxidized without an external electron acceptor is called fermentation.

What is Fermentation?
Fermentation is a metabolic process that occurs in the absence of oxygen, where organic compounds such as glucose are broken down into simpler molecules, producing energy in the form of ATP (adenosine triphosphate). Unlike aerobic respiration, which uses oxygen as the final electron acceptor, fermentation does not require an external electron acceptor.

Types of Fermentation:
There are two main types of fermentation: alcoholic fermentation and lactic acid fermentation.

1. Alcoholic Fermentation:
In alcoholic fermentation, glucose is converted into ethanol and carbon dioxide. It is commonly carried out by yeast and some bacteria. This process occurs in various biological processes, including the production of alcoholic beverages and the baking industry. The chemical equation for alcoholic fermentation is:

Glucose → 2 Ethanol + 2 Carbon Dioxide + ATP

2. Lactic Acid Fermentation:
In lactic acid fermentation, glucose is converted into lactic acid. This type of fermentation occurs in certain bacteria and animal cells, such as muscle cells during intense exercise when oxygen supply is limited. The chemical equation for lactic acid fermentation is:

Glucose → 2 Lactic Acid + ATP

Key Differences between Fermentation and Aerobic Respiration:
- Fermentation occurs in the absence of oxygen, while aerobic respiration requires oxygen.
- Fermentation produces a small amount of ATP compared to aerobic respiration.
- Fermentation does not require an external electron acceptor, whereas aerobic respiration uses an external electron acceptor (oxygen).
- Fermentation produces byproducts such as ethanol or lactic acid, while aerobic respiration produces carbon dioxide and water.

Conclusion:
The energy releasing metabolic process in which substrate is oxidized without an external electron acceptor is called fermentation. It is a vital process in various organisms and industries. Understanding the differences between fermentation and aerobic respiration helps us appreciate the diverse ways in which living organisms generate energy.

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