H1-antihistamines work by binding to histamine H1 receptors in mast cells, smooth muscle, and endothelium in the body as well as in the tuberomammillary nucleus in the brain; H2-antihistamines bind to histamine H2 receptors in the upper gastrointestinal tract, primarily in the stomach.
3 NADH molecules and 1 FADH molecule is produced for every turn of the Krebs cycle. One molecule of glucose will result in two turns of the Krebs cycle because two pyruvate molecules are the result of one glucose molecule (pyruvate if fed into the Krebs cycle after it is converted into acetyl-CoA).
When acetyl-CoA is oxidized to carbon dioxide in the Krebs cycle, chemical energy is released and captured in the form of NADH, FADH 2, and ATP. The electron transport chain allows the release of the large amount of chemical energy stored in reduced NAD + (NADH) and reduced FAD (FADH 2).