Adenine

Adenine (symbol A, or Ade) is a purine nucleotide base that is found in DNA, RNA, and ATP. It is usually a white crystalline subtance. The shape of adenine is complementary and pairs to either thymine in DNA or uracil in RNA. In cells, adenine is rare as an independent molecule. It is almost always covalently bound to become a part of a larger biomolecule. Adenine has a central role in cellular respiration. It is part of adenosine triphosphate which provides the energy that drives and supports most activities in living cells, such as protein synthesis, muscle contraction, and nerve impulse propagation. In respiration it also participates as part of the cofactors nicotinamide adenine dinucleotide, flavin adenine dinucleotide, and coenzyme A. It is also part of adenosine, adenosine monophosphate, cyclic adenosine monophosphate, adenosine diphosphate, and S-adenosylmethionine.