At the end of the Krebs cycle, the final product is oxaloacetic acid. This is identical to the oxaloacetic acid that begins the cycle. Now the molecule is ready to accept another acetyl-CoA molecule to begin another turn of the cycle. All told, the Krebs cycle forms (per two molecules of pyruvic acid) two ATP molecules, ten NADH molecules, and two FADH2 molecules.
If you take Regular insulin or a longer-acting insulin, you should generally take it 15 to 30 minutes before a meal. If you take insulin lispro (brand name: Humalog), which works very quickly, you should generally take it less than 15 minutes before you eat.
Short-acting insulin begins to lower blood glucose levels within 30 minutes, so you need to have your injection 30 minutes before eating. It has its maximum effect two to five hours after injection and lasts for six to eight hours.