Nucleoside diphosphates (NDPs) are organic molecules composed of a nucleoside linked to two phosphate groups. They play a crucial role in cellular metabolism and energy transfer. NDPs can be converted into nucleoside triphosphates (NTPs), which are essential for various biological processes, including DNA and RNA synthesis. The most common nucleoside diphosphates include ADP (adenosine diphosphate) and GDP (guanosine diphosphate). These molecules are involved in energy transfer within cells, acting as intermediates in the conversion of energy from food into usable forms. NDPs are vital for maintaining cellular functions and supporting life.