Question

The liver can convert some of the acetate generated by aldehyde dehydrogenase from ethanol into acetyl CoA. But acetyl CoA cannot be processed by the CAC, why?

Answer 1

Acetyl CoA cannot enter the citric acid cycle when oxaloacetate is limited, which can occur due to a high NADH/NAD+ ratio from alcohol metabolism or excessive fatty acid oxidation leading to ketone body production.

Step-by-step explanation:

The liver can indeed convert acetate from the metabolism of ethanol to acetyl CoA. However, under certain conditions, acetyl CoA cannot enter the citric acid cycle (CAC), also known as the tricarboxylic acid (TCA) cycle or Krebs cycle.

This is typically because the cycle requires oxaloacetate to combine with acetyl CoA to form citrate, which is the first step of the cycle. During heavy alcohol consumption, the high NADH/NAD+ ratio in liver cells due to ethanol metabolism inhibits the conversion of lactate to pyruvate and of pyruvate to oxaloacetate, limiting the substrates necessary for the CAC to operate.

Furthermore, excessive levels of fatty acid oxidation can lead to an accumulation of acetyl CoA, which the CAC cannot fully process, resulting in the production of ketone bodies such as acetoacetate, ß-hydroxybutyrate, and acetone.