Lactic Fermentation is one of two
anaerobic processes that can be used by a
cell to create
energy in the absense of
oxygen. During
lactic fermentation, the cell creates
pyruvate through two steps.
The first stage of this reaction is
glycolysis, which is the one stage of
cellular respiration that is common to all living
organisms. During glycolysis the
molecule glucose is broken into two molecules of
pyruvate. This molecule looks something like this:
O-
+
C=O
+
C=O
+
CH3
After glycoysis has been completed, the net products of the reactants are two molecules of pyruvate, two molecules of ATP and two molecules of NADH.
The two molecules of NADH that were produced during glycolysis are now used to fuel the second step of lactic fermentation. The two molecules of NADH are oxidized and the hyrdogen molecules that are freed are used to reduce the two molecules of pyruvate which creates two molecules of lactate, also know as lactic acid (see also: lactose). The products of this process looks like this:
O-
+
C=O
+
H-C-OH
+
CH3
Lactic Acid Fermentation has many important uses not only on a biological level, but on a utilitarian one as well. Because of the negative effects that it has on the body of mammals, alcoholic fermentation is not a possible means of producing energy within a cell when oxygen is not present. Not only would would the alcohol build up and destroy vital organs in the body, but the release of carbon dioxide during the process would also cause brain damage. Lactic Fermentation is free of both of these dangerous products.
If you have ever exercised you will know the effects that Lactic Acid has on the human body. The buring sensation that one encounteres after vigorous activity is caused by a build-up of Lactic Acid in the muscle tissue of the part of the body that has been worked. The cause for a cell to go through lactic fermentation rather than normal cellular respiration is due to the lack of oxygen in the blood because of a limited flow of circulation. While the heart speeds up during exercise, sometimes it is impossible for your heart to pump the necessary amount of blood through the muscles to supply them with oxygen, and so there is not enough oxygen for the cell to begin the Kreb's cycle. This forces the cell to use other means to obtain the ATP needed to function. This lactic acid is later carried away by the blood and transported to the liver where it is broken down.
Also, if you have ever eaten cheese or yogurt, you have benefitted from lactic fermentation in another way. Both of these dairy products are created through lactic acid fermentation in various fungi and bacteria.
Net ATP gained= 2
Primary Source: Biology, Sixth Addition by Campbell and Reece