Final answer:
Acetyl CoA, formed through the metabolism of fatty acids, enters the citric acid cycle (Krebs cycle) where it contributes to ATP production and is not involved in glycolysis, the electron transport chain initiation, or conversion to pyruvate and lactate.
Step-by-step explanation:
When fatty acids are metabolized for cellular respiration and form acetyl CoA, the correct next step is that acetyl CoA enters the citric acid cycle. The process of fatty acid metabolism, also known as beta-oxidation, involves the removal of two carbon atoms at a time from fatty acid chains to form acetyl CoA. Once the acetyl CoA is formed, it is not used in glycolysis, nor does it start the electron transport chain directly, nor is it converted to pyruvate and lactate. Instead, it combines with oxaloacetate in the Krebs cycle to initiate a series of reactions that eventually lead to ATP production.
The Krebs cycle, also known as the citric acid cycle or TCA cycle, is a crucial stage in cellular respiration following glycolysis in the presence of oxygen. Acetyl CoA's entry into the Krebs cycle is essential for harvesting the substantial energy stores present within the fatty acid molecules, ending with the release of carbon dioxide, the production of NADH and FADH2, and the generation of ATP through substrate-level phosphorylation and oxidative phosphorylation.