Question

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

Answer 1

Hint: 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.