# NAD
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**NAD**, or **nicotinamide adenine dinucleotide**, is a [[vitamin B]] [[cofactor]] central to [[metabolism]] as an [[electron carrier]].
![[nad diagram.png]]
## Structure
It is called a "dinucleotide" because it is made up of two [[nucleotide|nucleotides]], "nicotinamide" and "adeninie". These are bonded between their phosphate groups. It is structurally similar to [[adenosine triphosphate]] in some ways, considering the adenine base, but it only has two phosphate groups, which allow [[redox]] to occur much more eaisly.
ATP is a building block for NAD.
## Forms
NAD has two main forms, the reduced from *NADH* and it's oxidized form *NAD+*.
**NAD+** is the [[redox|oxidized]] (or "empty") form of NAD. When it becomes reduced and accepts electrons it becomes NADH, which is the [[electron carrier|electron carrying]] from. It is reduced during the [[citric acid cycle]].
**NADH** is the [[electron carrier]] form of NAD. It is the [[redox|reduced]] (or "full") form of NAD+. It plays a vital role in the [[ETC (mitochondria)]], where it oxidizes some protein complexes.
NAD becomes **[[NADP]]** with the addition of a phosphate group.
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