The Krebs Cycle, also known as the Citric Acid Cycle or Tricarboxylic Acid (TCA) Cycle, is a series of chemical reactions that occur in the mitochondria. It takes place in three stages: cis-citrate cycle, isocitrate cycle, and oxaloacetate cycle. During these cycles, acetyl-CoA molecules are converted into carbon dioxide, releasing energy that is used to produce ATP (adenosine triphosphate), the primary energy currency of cells. The Krebs Cycle also produces NADH and FADH2, which are used in the electron transport chain to generate more ATP.