Question

Conversion of pyruvic acid into ethyl alcohol is mediated by
A) Phosphatase
B) Dehydrogenase
C) Decarboxylase and dehydrogenase
D) Catalase

Answer 1

Pyruvic acid is first transformed to acetaldehyde during the fermentation of alcohol. Acetaldehyde is then converted to ethyl alcohol.

Complete answer:
First we should know about fermentation to answer this question. Fermentation is a biochemical mechanism carried out by a wide variety of species that transforms sugar to acids, gases, or alcohol. As in the muscles of higher vertebrates, yeast and other microorganisms ferment glucose into ethanol and $CO_2$, instead of lactate. By glycolysis, glucose is transformed to pyruvate, and pyruvate is transformed to ethanol and $CO_2$ in a two-step process.
Now, let us find the solution from the options-

Pyruvate is decarboxylated in the first step in an irreversible reaction that is catalysed by pyruvate decarboxylase. Pyruvate is converted to acetaldehyde in the presence of pyruvate decarboxylase. > Pyruvate decarboxylase needs $Mg^{2 +}$ and has a coenzyme, thiamine pyrophosphate, which is closely bound.
In the second step, by the activity of alcohol dehydrogenase, acetaldehyde is reduced to ethanol, with the decreasing power given by NADH obtained from the dehydrogenation of glyceraldehyde 3-phosphate. Therefore, ethanol and $CO_2$ are the final components of ethanol fermentation.
From these we came to know that only option B is not correct and the options A and D are incorrect.

Thus, the correct answer is option C Decarboxylase and dehydrogenase.

Note: Two enzymes, carboxylase and carboxykinase, are needed to convert pyruvic acid back to phosphoenolpyruvate ( PEP). Pyruvic acid is either transformed to ethanol in alcohol fermentation or lactate in lactate fermentation under anaerobic conditions.