Give two examples where lactic acid is formed by fermentation.
Answers
Fermentation is a metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of respiration. In the context of food production, it may more broadly refer to any process in which the activity of microorganisms brings about a desirable change to a foodstuff or beverage. The science of fermentation is known as zymology.
EXAMPLE OF FERMENTATION
In ethanol fermentation, one glucose molecule is converted into two ethanol molecules and two carbon dioxide molecules.It is used to make bread dough rise: the carbon dioxide forms bubbles, expanding the dough into a foam.The ethanol is the intoxicating agent in alcoholic beverages such as wine, beer and liquor.Fermentation of feedstocks, including sugarcane, corn, and sugar beets, produces ethanol that is added to gasoline.In some species of fish, including goldfish and carp, it provides energy when oxygen is scarce (along with lactic acid fermentation).
The figure illustrates the process. Before fermentation, a glucose molecule breaks down into two pyruvate molecules. The energy from this exothermic reaction is used to bind inorganic phosphates to ADP, which converts it to ATP, and convert NAD+ to NADH. The pyruvates break down into two acetaldehyde molecules and give off two carbon dioxide molecules as a waste product. The acetaldehyde is reduced into ethanol using the energy and hydrogen from NADH, and the NADH is oxidized into NAD+ so that the cycle may repeat. The reaction is catalysed by the enzymes pyruvate decarboxylase and alcohol dehydrogenase.