In the context of nucleic acids, ATP is structurally most similar to which type of molecule?

• A. A pyrimidine nucleotide (e.g., cytidine triphosphate)
• B. A nucleic acid polymer (a long chain of nucleotides such as DNA or RNA)
• C. A deoxyribonucleoside (adenine attached to deoxyribose with no phosphate groups)
• D. A ribonucleotide (adenosine triphosphate is a purine nucleoside with three phosphate groups)

Answer: (D)