3.0 Lactic Acid Fermentation 3.1 Types of Fermentation 3.2 Energy Produced from Lactic Acid Fermentation
| 4.0 Anaerobic Exercise 4.1 Benefits of Anaerobic Exercise 4.2 Anaerobic threshold (AT) 4.3 Male vs. female anaerobic exercise characteristics
| 5.0 Conclusion
Respiration usually occurs in two ways, aerobically and anaerobically. Aerobic respiration uses oxygen to function and anaerobic respiration functions without oxygen. Generally, anaerobic respiration starts by breaking down the molecules of glucose and produces pyruvic acid. The pyruvic acid then undergoes fermentation to produce ATP, the basic energy source in our human body.
Although this kind of respiration is less efficient in producing energy, because it produces only two ATP molecules in comparison to the 38 molecules produced during aerobic respiration, however, this form of respiration is very primitive and had actually started from the time when oxygen was missing in our atmosphere. Many living organisms have successfully adapted to anaerobic form of respiration to survive due to insufficient of oxygen supply.
3.0 Lactic Acid Fermentation
Lactic acid fermentation of human beings is the simplest type of fermentation for which is a typical redox reaction. In anaerobic conditions, the primary mechanism of ATP production of a cell is glycolysis. Glycolysis will transfer electron (reduction) to NAD+, forming NADH. However, during lactic acid fermentation, the supply of NAD+ is limited in a cell. For glycolysis to continue, NADH must be oxidized (gives away electron) to regenerate the NAD+. This is done through an electron transport chain in oxidative phosphorylation in a condition that there is the presence of oxygen.
NADH will donate the extra electrons to the pyruvate molecules during glycolysis. Since the NADH has lost electrons, NAD+ is being regenerated to undergo glycolysis. Lactic acid, C3H6O3 is formed by the reduction of pyruvate molecules.
3.1 Types of Fermentation
There are two types of fermentation processes which may take place in the absence of oxygen after the glycolysis process, either heterolactic acid fermentation or homolactic fermentation. In heterolactic acid fermentation, glucose molecule is converted into lactate, ethanol and carbon dioxide. The reaction proceeds as follows, with one molecule of glucose being converted to one molecule of lactic acid, CH3CHOHCOOH, one molecule of ethanol, C2H5OH, and one molecule of carbon dioxide, CO2 which is also known as alcohol fermentation as ethanol is being produced. The equation for this reaction is as follow:
C6H12O6 → CH3CHOHCOOH + C2H5OH + CO2
On the other hand, homolactic fermentation breaks down the pyruvate into lactate. It occurs in the muscles of animals when they need energy faster than the blood can supply oxygen. It also occurs in some kinds of bacteria and some fungi. The bacteria convert lactose into lactic acid, for example, in the production of yogurt, giving the sour taste of yogurt. These lactic acid bacteria can be classed as homofermentative, where the end-product is mostly lactate, or heterofermentative, where some lactate is further metabolized and results in carbon dioxide, acetate, or other metabolic products. Heterolactic acid fermentation is unique because it is a respiration process which does not produce a gas as a byproduct. There are two possible outcomes, either one molecule of glucose is converted to two molecules of lactic acid, CH3CHOHCOOH: C6H12O6 → 2 CH3CHOHCOOH
Or, one molecule of lactose, C12H22O11 and one molecule of water reacted to form four molecules of lactate (as in yogurts and cheeses): C12H22O11 + H2O → 4 CH3CHOHCOOH
3.2 Energy Produced from Lactic Acid Fermentation
The overall equation...
References: Reference Guide to Anaerobic Exercise An In-Depth Look at High Intensity Exercise, Jen Mueller and Nicole Nichols, Fitness Experts
Anaerobic Respiration, Aharon Oren, The Hebrew University of Jerusalem, Jerusalem, Israel, September 2009, pp 123-136.
Anaerobic Respiration, Frederic P Miller, Agnes F Vandome, John McBrewster, VDM Publishing House Ltd., 2010, pp 67-78.
Biochemistry 2nd Edition, by Keshav Trehan, 1990, New Age International, pp 327-338.
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