Is a coenzyme found in all living cells. The compound is a dinucleotide, because it consists of two nucleotides joined through their phosphate groups. One nucleotide contains an adenine base and the other nicotinamid. Nicotinamide adenine dinucleotide exists in two forms, an oxidized and reduced form abbreviated as NAD+ and NADH respectively. NAD participates in many redox reactions in cells, including glycolysis and most of those, the citric acid cycle of cellular respiration [Wiki]