Download Lactic Acid Fermentation

Alcohol Fermentation
-necessary in prokaryotes due to no mitochondria and in yeast when the oxygen is
gone.
As you can see in the above diagram, Glycolysis makes 2 ATP (net) and 2 NADH
which would normally be used in the ETC but there are no ETC in prokaryotes and
there is no oxygen available for yeast so the NADH builds up and NAD+ runs out. If
NAD+ runs out, glycolysis itself will stop and there will be NO ATP made again. This
will cause the organism to die.
Therefore, a recycling program is needed to get the NADH back to NAD+. In alcohol
fermentation, the pyruvate breaks down into Ethanol (alcohol) as it gives off one
carbon dioxide (per pyruvate) while accepting two electrons from NADH. This
breaks down NADH into NAD+ so that it can be used by Glycolysis again and again.
In bacteria (prokaryotes), this has to happen because there are no mitochondria to
pass the NADH to for the recycling of NAD+.
This is the process that allows beer and wine makers to produce alcoholic beverages
by putting yeast in with the fruits and sugars specific to the beverage.
Lactic Acid Fermentation
-necessary to recycle NADH back into NAD+ when oxygen is not available in humans
In animals, especially humans, when there is a high demand for oxygen and it is not
getting to the cells fast enough, the NADH builds up and the cell runs out of NAD+ in
glycolysis to make ATP. With no oxygen available to the last step of the ETC, then
there is no place for the NADH to drop off it’s electrons. This occurs when your
activity level exceeds your body’s ability to bring in oxygen fast enough to supply
the ETC in the mitochondria.
The solution, so that you get at least some ATP from glycolysis, is to skip the
mitochondria all together and recycle the NADH into NAD+ through lactic acid
fermentation.
When pyruvate is made, it is converted into lactic acid (lactate) while accepting 2
electrons from NADH. Once this occurs, the NADH falls apart into NAD+ and H+
thereby making NAD+ available so that at least glycolysis can continue to provide
you with some ATP instead of none.
The lactic acid is secreted by the cells into the surrounding space where your nerves
happen to be which causes you to feel a burning sensation in the areas of the
muscles that were in oxygen debt.