Acetyl CoA is the common intermediate at which the breakdown pathways of fats, carbohydrates, and proteins converge. Specifically, fatty acids from fats are broken down directly into Acetyl CoA before entering the Krebs cycle . Carbohydrates are converted to glucose and then pyruvic acid, which is oxidatively decarboxylated to form Acetyl CoA . Proteins are broken into amino acids, which, depending on their structure, can enter the respiratory pathway as pyruvate or Acetyl CoA . Figure 12.6 in the source material confirms that Acetyl CoA is the common entry point for all three .