Nucleosides are organic molecules that consist of a nitrogenous base attached to a sugar molecule, specifically a pentose sugar. They are fundamental components of nucleotides, which are the building blocks of nucleic acids like DNA and RNA. Nucleosides play a crucial role in various biological processes, including energy transfer and signaling. In the body, nucleosides can be phosphorylated to form nucleotides, which are essential for cellular functions. They can also serve as precursors for the synthesis of ATP, the primary energy carrier in cells. Additionally, some nucleosides have therapeutic applications, such as in antiviral and anticancer treatments.