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).
Nicotinamide adenine dinucleotide (NAD) is one of the most important coenzymes in the cell. Not surprisingly, NAD and the closely related NADP are the two most abundant cofactors in eukaryotic cell. Healthy bodies make all the NADH they need using vitamin B3 (also known as niacin, or nicotinamide) as a starting point.