Adenosine is a nucleoside, which is a molecule composed of a nitrogenous base (in this case, adenine) and a sugar (ribose in this case). It is one of the four nucleosides that make up nucleic acids, such as DNA and RNA. Adenosine plays a crucial role in cellular processes as a component of adenosine triphosphate (ATP), which is a primary energy carrier in cells. Additionally, adenosine is involved in various physiological functions, including neurotransmission and regulation of blood flow. It serves as a signaling molecule and can have effects on the central nervous system, including acting as a neuromodulator.

Cytidine is a nucleoside, composed of the nucleobase cytosine and the sugar ribose. It is a building block of nucleic acids, being one of the four nucleosides that make up RNA (ribonucleic acid). In RNA, cytidine pairs with guanine. Cytidine has various biological roles, including its involvement in the synthesis of nucleic acids, the transmission of genetic information, and as a component of certain coenzymes.

Guanosine is a nucleoside, consisting of the nucleobase guanine and the sugar ribose. It is one of the building blocks of nucleic acids, specifically RNA (ribonucleic acid). In RNA, guanosine pairs with cytidine. Beyond its role in RNA, guanosine is involved in various cellular processes, serving as a key component in the synthesis of nucleic acids.

Inosine is a nucleoside, composed of the nucleobase hypoxanthine and the sugar ribose. It is one of the naturally occurring nucleosides found in RNA (ribonucleic acid). Inosine can form during the degradation of adenosine in RNA. Inosine has various roles in cellular processes. It is involved in the wobble base pairing during protein synthesis, where it can pair with adenine, cytosine, or uracil. This flexibility in base pairing contributes to the versatility of the genetic code.

Uridine is one of the four standard nucleosides that make up RNA (ribonucleic acid). It is composed of a ribose sugar molecule, a phosphate group, and the nitrogenous base uracil. Uridine contains a pentose sugar known as ribose. The ribose sugar is a five-carbon sugar that forms the backbone of the nucleotide.