1. Fermentation
Fermentation is releasing energy in the absence of oxygen. It is an ANAEROBIC process.
Occurs in the cytoplasm.
There are two main types of fermentation
Alcoholic Fermentation
Lactic Acid Fermentation
During Fermentation, cells convert NADH to NAD+, allowing glycolysis to continue.

2. Alcoholic Fermentation
Alcoholic fermentation is found in Yeasts,
and a few other microorganisms.
Causes bread to rise
The equation is:
Pyruvic acid + NADH  alcohol + CO2 + NAD+
Note: Carbon Dioxide is also produced!
When yeast in the dough runs out of oxygen, it begins to ferment, giving off bubbles of carbon dioxide that form the air.

3. Alcoholic Fermentation

5. Lactic Acid Fermentation
Takes place in animal cells
Pyruvic acid from glycolysis can be
converted to lactic acid.
This conversion regenerates NAD+ for glycolysis to continue
The equation is:
Pyruvic acid + NADH  lactic acid + NAD+
Lactic acid is created by unicellular organisms in the production of cheese, pickles, kimchi and other foods.
Lactic acid is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to the tissues. But lactic acid does not directly cause muscle burn or soreness!!
Through Lactic Acid Fermentation, ATP is made very quickly which causes a drop in the pH. This pH drop is what causes muscle burn.
If you continue to exercise, then you will tear your muscles and cause muscle soreness.

6. Muscle soreness
Lactic acid is produced in your muscles during rapid exercise when the body cannot supply enough oxygen to the tissues. But lactic acid does not directly cause muscle burn or soreness!!
Through Lactic Acid Fermentation, ATP is made very quickly which causes a drop in the pH. This pH drop is what causes muscle burn.
If you continue to exercise, then you will tear your muscles and cause muscle soreness.

7. Lactic Acid Fermentation
Lactic Acid fermentation diagram

8. Energy use by humans Cells contains small amounts of ready ATP
About 5 seconds worth
After that, your body uses lactic acid formation
This lasts for about 90 seconds
You breathe hard to get rid of the lactic acid buildup
For exercise longer than 90 seconds, cellular respiration is used
This is a slow method to generate ATP
Glycogen (a form of carbohydrate) is used for the first minutes of cellular respiration
After that other molecules, such as fats, are broken down