Question

During anaerobic respiration, the conversion of pyruvate into acetaldehyde, along with coenzyme TPP, the cofactor required is
A) $Mg^{++}$
B) $Mn^{++}$
C) $Fe^{++}$
D) $Zn^{++}$

Answer 1

Hint: Anaerobic respiration is the breakdown of food to liberate energy in the absence of oxygen. It is less efficient than aerobic respiration. It is also called alcoholic fermentation. It takes place in yeast.

Complete answer:
To answer this question we must know about the anaerobic respiration in yeast. Under anaerobic conditions, yeast undergoes alcoholic fermentation in which the pyruvate is converted to acetaldehyde which is further converted to ethanol. This reaction is an enzymatic reaction which is catalysed by the enzyme Pyruvate decarboxylase.

Reaction steps:
i) The first step is conversion of pyruvate to acetaldehyde in the presence of enzyme pyruvate decarboxylase. The enzyme depends on the cofactor thiamine pyrophosphate (TPP) and magnesium. This enzyme is a decarboxylase which produces acetaldehyde along with carbon dioxide.
ii) The acetaldehyde is converted to ethanol in the presence of alcohol dehydrogenase to liberate ethanol.
$Mn^{++}$ is used as a cofactor to the enzyme pyruvate carboxylase.
$Fe^{++}$ is used as a cofactor in the electron transfer chain.
$Zn^{++}$ is used as a cofactor which is called metalloenzyme. It is used as a cofactor in the alcohol dehydrogenase activity.

Thus the correct answer is option ‘A’. $Mg^{++}$ is the cofactor required along with coenzyme TPP.

Note: The cofactors are the helper molecules which assist an enzymatic reaction. It is a non-protein compound or a metallic ion which helps in activating the catalyst.