Question

Which of the following organic acids is produced by fermentation?
A. Oxalic acid
B. Lactic acid
C. Citric acid
D. Propionic acid

Answer 1

Hint: Fermentation is essentially an important biochemical reaction or metabolic process that induces chemical changes in organic matter (substrates) by the action of specific enzymes. In simple words, this process is carried out for the extraction of energy in the form of ATP molecules, from carbohydrate substrates, in the absence of oxygen.

Complete answer: Lactic acid fermentation is a metabolic pathway carried out in cells, by which glucose or any other six-carbon sugars (such as sucrose or lactose) get readily oxidized followed by the subsequent release of cellular energy and release lactic acid as a byproduct. This type of fermentation is beneficial in anaerobic bacteria because they convert glucose into 2 ATP molecules, which is basically the main energy currency cells use to carry out life processes. Lactic acid fermentation usually occurs in muscles during fatigue. For example during a heavy workout, i.e. when the muscle is devoid of oxygen, the lactic acid starts accumulating in muscle cells. It not only occurs in muscle cells, but it can also be witnessed in bacteria. In fermentation, Bacteria convert glucose into two molecules of lactate and use this reaction to perform substrate-level phosphorylation to make two molecules of ATP. The main enzyme involved in the reaction is lactate dehydrogenase.
Hence, the correct answer is option B.

Note: It is important to note that the carboxylic acid produced in muscle cells is transported through the bloodstream to the liver, where it's converted back to pyruvate and processed normally within the remaining reactions of respiration.