Chapter 8, Problem 1Q

Summary Introduction

To review:

The production of a large amount of NADH (reduced form of nicotinamide adenine dinucleotide or NAD) leading to lactate accumulation in an individual, as a result of alcohol intoxication.

Introduction:

Alcohol is one of the most common mood-altering drugs used by individuals. However, alcohol is a toxic drug, which is capable of causing damage to liver tissues and in severe cases, death of the individual. Thus, the body has evolved certain mechanisms to reduce the damage through the oxidation of consumed alcohol (ethanol).

Explanation of Solution

The metabolism of ethanol occurs in the liver of an individual. The oxidation of ethanol produces acetaldehyde, which is further oxidized to form acetic acid along with carbon dioxide and water. Further, both the oxidation processes result in the production of a large amount of NADH. This is because alcohol has no or negligible nutrient content and thus, cannot be stored in the body.

The NADH thus produced is utilized for the conversion of pyruvic acid to lactic acid (lactate) along with the production of NAD⁺ as a byproduct. The equation has been described below:

$\text{Pyruvate}+\text{NADH}+{\text{H}}^{\text{+}}\to \text{Lactate}+{\text{NAD}}^{\text{+}}$

Hence, lactate or lactic acid accumulation is commonly observed as a side-effect of alcohol intoxication. Furthermore, synthesized NAD⁺ participates in the glycolysis reaction for the production of energy.

Conclusion

Therefore, it can be concluded that the fate of the NADH (that is, the conversion of pyruvate to lactate), which is formed as a result of oxidation of ethanol and acetaldehyde, leads to the accumulation of lactate in an individual.