In biochemistry, a ribonucleoside is an organic molecule derived from the condensation of a nitrogenous base and the C1 atom of ribose via a glycoside linkage. Examples of pyrimidine ribonucleosides include uridine and cytidine. Thymine ribonucleoside is sometimes called 5-methyluridine, while thymidine represents deoxynucleoside of thymine. Pyrimidine ribosides are linked via their N1 nitrogen atoms. The purine ribosides include adenosine and guanosine, linked via their N9 ring atoms. The glycoside linkage may be α- or β-, depending on which face of the ribose ring the nitrogen heterocycle is bonded on. Biological ribosides are β-linked. Nucleosides are phosphorylated to give nucleotides.