Final answer:
In the Krebs cycle, the 2-carbon fragment of acetyl-CoA is added to oxaloacetate to make citrate (or citric acid). The conversion of acetyl-CoA to citrate is the first step of the Krebs cycle and leads to a series of reactions that generate energy in the form of electron carriers and ATP or GTP.
Step-by-step explanation:
In the Krebs (TCA) cycle, the 2-carbon fragment of acetyl-CoA is added to oxaloacetate to make citrate (or citric acid). The acetyl-CoA molecule enters the Krebs cycle by combining with a four-carbon molecule known as oxaloacetate. This reaction results in the formation of a six-carbon molecule called citrate, or citric acid, and at the same time, it releases the coenzyme A molecule.
Detailed steps of the Krebs cycle include the oxidative decarboxylation of citrate, which leads to the release of carbon dioxide and the generation of high-energy electron carriers such as NADH and FADH₂, along with ATP or GTP (depending on the cell type). These energy carriers are produced through a series of reactions as part of the cycle. The Krebs cycle plays a crucial role in cellular respiration by processing the acetyl-CoA derived from carbohydrates, fats, and proteins into energy and by releasing carbon dioxide as a waste product.