Cytidine

As one of the four building blocks (nucleosides) of nucleic acids, life as we know it would not exist without cytidine (abbreviated C by biochemists and molecular biologists). A pyrimidine nucleoside similar to thymidine (T) in DNA or uridine (U) in RNA, cytidine is an aromatic single-ring nitrogen heterocycle (cytosine) bonded to a ribose sugar unit. In nucleic acids, pyrimidine nucleosides are hydrogen bonded to purines (guanidine (G) and adenosine (A)).