Anaerobic respiration allows cells to obtain energy without oxygen through fermentation, which results in fewer ATP molecules than aerobic respiration. There are two main types of fermentation: lactic acid fermentation, occurring in muscle cells during intense exercise, and alcohol fermentation, primarily in yeasts. Fermentation is also essential for producing various foods and beverages.

1. Anaerobic Respiration - Fermentation
13.1 Ecologists Study Relationships
Anaerobic Respiration

2. Anaerobic Respiration - Fermentation
• If no oxygen is available, cells can obtain energy
through the process of anaerobic respiration.
• A common anaerobic process is fermentation.
• Fermentation is not an efficient process and results in
the formation of far fewer ATP molecules than aerobic
respiration.
There are two primary fermentation processes:
1. Lactic Acid Fermentation
2. Alcohol Fermentation

3. Anaerobic Respiration - Fermentation
Lactic acid fermentation occurs when oxygen is not
available.
For example, in muscle tissues during rapid and vigorous
exercise, muscle cells may be depleted of oxygen. They
then switch from respiration to fermentation.

4. Anaerobic Respiration - Fermentation
The Pyruvic acid formed during Glycolysis each gain a
hydrogen from NADH.
The new hydrogen turn the Pyruvate into lactic acid and
energy is released (which is used to form ATP).
Glucose → Pyruvic acid → Lactic acid + energy

5. Anaerobic Respiration - Fermentation
•The process of lactic acid fermentation replaces the
process of aerobic respiration so that the cell can have a
continual source of energy, even in the absence of oxygen.
•However this shift is only temporary and cells need
oxygen for sustained activity.

6. Anaerobic Respiration - Fermentation
•When you exercise vigorously Lactic acid builds up in the
tissue causing a burning, painful sensation.
•You must breath in more Oxygen to replenish the O2 in
your muscles.

7. Anaerobic Respiration - Fermentation
Alcohol fermentation occurs in yeasts and some
bacteria.
Pyruvic acid formed during glycolysis is broken down
to produce alcohol and carbon dioxide and is released
(which is used to form ATP).

8. Anaerobic Respiration - Fermentation
In Fermentation the Pyruvate made during Glycolysis loses
another carbon making carbon dioxide.
The two sets of carbons left each gain a hydrogen from NADH.
This turns the two carbon chains into Ethyl Alcohol.
Glucose → Pyruvic acid → alcohol + carbon dioxide + energy

9. Anaerobic Respiration - Fermentation
• Fermentation is used in food production.
– Yogurt - Soy Sauce
– Cheese - Vinegar
– Bread - Olives/Pickles
– Beer/ Meade - Wine/ Ale
– Sauerkraut - Malt

10. Anaerobic Respiration - Fermentation