What is lactic acid fermentation?

Lactic acid fermentation is a type of anaerobic respiration in which glucose is partially broken down into lactic acid in the absence of oxygen, producing a small amount of energy.

It occurs in muscle cells of humans and in certain bacteria.

Process of lactic acid fermentation:

1. Glycolysis
Glucose is converted into pyruvate in the cytoplasm, producing:

• 2 ATP (net gain)

• 2 NADH

2. Conversion to lactic acid
In the absence of oxygen, pyruvate is reduced to lactic acid.
This step regenerates NAD⁺, which is necessary for glycolysis to continue.

3. Continuation of energy production
The regenerated NAD⁺ allows glycolysis to keep producing ATP, even without oxygen.

Key features:

• Occurs without oxygen

• Produces only 2 ATP per glucose

• Does not involve mitochondria

Where it occurs:

• Human muscle cells during intense exercise

• Lactic acid bacteria (used in curd/yogurt formation)

Effects:

• Accumulation of lactic acid causes muscle fatigue and cramps

• Lactic acid is later broken down when oxygen becomes available

Importance:

• Provides quick energy in low oxygen conditions

• Used in food production like curd and fermented products

In simple terms: Lactic acid fermentation produces a small amount of energy without oxygen by converting glucose into lactic acid.