What is formed when Acetyl CoA enters the Krebs cycle?

When Acetyl CoA enters the Krebs cycle, it combines with a four-carbon molecule called oxaloacetate to form citrate, a six-carbon compound. This reaction is catalyzed by the enzyme citrate synthase and is the first step of the Krebs cycle. The formation of citrate is crucial as it initiates the series of reactions that will ultimately lead to the regeneration of oxaloacetate, allowing the cycle to continue and facilitating the production of energy in the form of ATP, NADH, and FADH2. This process contributes to the overall function of cellular respiration, which is key in energy production for the cell.