Correct option is A
.Ans. (a) The direction of L-ADH reaction varies with the relative concentrations of acetaldehyde and ethanol. In addition, the enzyme metabolizes the alcohols produced by intestinal microflora anaerobically.
Sol. The physiological significance of Liver Alcohol Dehydrogenase (L-ADH) is primarily related to its role in ethanol metabolism, especially under anaerobic conditions or in situations where fermentation is not occurring in the liver. In mammals, ethanol is metabolized by L-ADH, which converts ethanol to acetaldehyde and subsequently to acetic acid. The direction of the L-ADH reaction is highly dependent on the concentration of acetaldehyde and ethanol. Under certain conditions, where acetaldehyde concentration is high, L-ADH may metabolize ethanol to acetaldehyde. Additionally, L-ADH plays a role in metabolizing alcohols produced by intestinal microflora anaerobically, thus playing a significant role in maintaining the homeostasis of alcohol metabolites.
Information Booster
Liver Alcohol Dehydrogenase (L-ADH) is involved in the oxidation of ethanol to acetaldehyde and acetaldehyde to acetate, which is then further metabolized to Acetyl-CoA, entering the citric acid cycle. This process helps to detoxify alcohol and maintain physiological balance when alcohol is consumed. L-ADH's activity is highly influenced by the concentrations of ethanol and acetaldehyde, with the enzyme being able to switch between the two reactions depending on the relative concentration of these compounds.
L-ADH also plays a crucial role in the metabolism of alcohols produced by the gut microbiome. These alcohols, produced through fermentation, are absorbed and metabolized by the liver, where L-ADH helps to prevent their accumulation by converting them to less toxic compounds.
Additional Information
(b) NAD⁺ produced by L-ADH drives glycolysis in the liver:
This option is incorrect because the NAD⁺ produced by L-ADH does not directly drive glycolysis in the liver. While NAD⁺ is a cofactor in glycolysis, the role of L-ADH in NAD⁺ production is mainly associated with the oxidation of alcohols rather than directly promoting glycolytic pathways.
(c) Mammalian L-ADH converts pyruvate to lactate and the NAD⁺ thus generated drives glycolysis:
This is inaccurate as L-ADH does not convert pyruvate to lactate; instead, lactate dehydrogenase (LDH) catalyzes this reaction. L-ADH’s primary role involves alcohol metabolism, not the conversion of pyruvate to lactate.
(d) Mammalian L-ADH has non-metabolic moonlighting functions:
While L-ADH may have some regulatory roles in various processes, this option is incorrect in the context of the question. The main role of L-ADH in the liver is metabolic, specifically related to the detoxification of alcohols and acetaldehyde. Non-metabolic moonlighting functions are not its principal physiological significance.
