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).
NADH and FADH (products of the citric acid cycle) are processed in the mitochondria by removing the hydrogen atoms (electrons and protons) and combining them with oxygen form water molecules H2O. the mitochondria process the NADH and FADH to produce ATP energy. Each NADH produces 3 ATP. Each FADH produces 2 ATP.