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What is adenosine diphosphate (ADP) predominantly composed of?

  1. A nitrogenous base and three phosphate groups

  2. A nitrogenous base, a pentose sugar, and two phosphate groups

  3. A pentose sugar and one phosphate group

  4. A nitrogenous base, a pentose sugar, and three phosphate groups

The correct answer is: A nitrogenous base, a pentose sugar, and two phosphate groups

Adenosine diphosphate (ADP) is predominantly composed of a nitrogenous base, a pentose sugar (specifically ribose), and two phosphate groups. The nitrogenous base in ADP is adenine, which is crucial for the molecule's function in energy transfer within cells. The ribose sugar forms the backbone structure of the molecule, connecting the nitrogenous base to the phosphate groups. The presence of two phosphate groups, as opposed to three found in ATP (adenosine triphosphate), indicates its role in energy metabolism. When ADP is phosphorylated to become ATP, it serves as a key energy source for various biological processes.