The Krebs cycle involves a series of enzymatic reactions that convert carbohydrates, fats, and proteins into ATP, the energy currency of cells. It starts with the acetyl-CoA molecule, derived from the breakdown of glucose or fatty acids, combining with a four-carbon molecule called oxaloacetate to form a six-carbon molecule called citrate. The citrate molecule then undergoes a series of chemical transformations, resulting in the formation of three molecules of NADH, one molecule of FADH2, one molecule of ATP, and two molecules of CO2.

The NADH and FADH2 molecules produced in the Krebs cycle are crucial for the electron transport chain, the final stage of cellular respiration. These molecules donate electrons to the chain, which generates a proton gradient across the inner mitochondrial membrane. This gradient drives the synthesis of ATP through a process called oxidative phosphorylation.

Overall, the Krebs cycle plays a major role in producing ATP, which provides energy for various cellular processes. Additionally, it generates NADH and FADH2, which participate in oxidative phosphorylation. The cycle is essential for the efficient utilization of carbohydrates, fats, and proteins as energy sources in living organisms.