By: Kelly Song
Fermentation is the metabolic process in which energy is extracted from carbohydrates in the absence of oxygen. However, in most living things, energy is created by a process called cellular respiration. This process has three main stages; glycolysis, oxidation of pyruvate, the Kreb cycle, and electron transport. The Kreb cycle and electron transport both require oxygen, and are not involved in fermentation. There are two main types of fermentation: Lactic acid and alcoholic (aka ethanol).
Lactic Acid Fermentation:
One example of lactic acid fermentation is found in human cells. Lactic acid is best known as the waste product our muscles produce when they are fatigued. When people exercise intensely, there comes a point where there is not enough oxygen that is provided for aerobic respiration. Therefore, our muscle cells rely on another process that can provide ATP without it: fermentation. As mentioned before, fermentation starts off after the oxidation of pyruvate. In this specific process, two pyruvateand two ATP molecules occur from the splitting of glucose during glycolysis. The two pyruvateallows the two NADH to oxidize to NAD+, eventually leading to two lactate. Although fermentation is an alternative, it is not nearly as efficient as aerobic respiration. Additionally, in humans, the build-up of lactic acid in the muscles causes a burning sensation that tells us it is time to stop. Rest allows the cells to recover and receive the oxygen they need once more.
Alcoholic Fermentation:
The process of alcoholic fermentation is similar to that of lactic acid. However, humans cannot perform alcoholic fermentation because we lack the genetic information to do so. There are two pyruvate and two ATP molecules that are produced from glycolysis. The breakdown of pyruvateresults in acetaldehyde, carbon dioxide, and ethanol. Living organisms like yeast use this process to produce the waste product of carbon dioxide. Humans then take advantage of the alcoholic fermentation that occurs in yeast to make things such as bread. Additionally, humans also use this process to their full advantage by making things such as yogurt, wine, beer, and kimchi, among many others.
In simple terms, fermentation is the process in which substances produce energy without the presence of oxygen. Not only is lactic acid fermentation needed in the human body, but alcoholic fermentation is something that humans use and profit off of. Fermentation is one of the many necessary building blocks in the world.
Grewal, Suzanne. “5.10: Fermentation.” Libretexts, 21 Dec. 2018, https://bio.libretexts.org/Bookshelves/Human_Biology/Book%3A_Human_Biology_(Wakim_and_Grewal)/05%3A_Cells/5.10%3A_Fermentation.
https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/alcoholic-fermentation#:~:text=Alcoholic%20fermentation%20is%20a%20complex,properties%20of%20the%20fermented%20foodstuffs.
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