ATP Structure: Ribonucleotide with Triphosphate

Steps:

• Identify ATP as adenosine triphosphate, composed of a nitrogenous base, sugar, and phosphate groups.
• Recall the base is adenine (purine, in both DNA/RNA) and sugar is ribose (5-carbon sugar in RNA).
• Confirm phosphate count: ATP has three phosphate groups linked in a chain.
• Match to options: RNA indicates ribose sugar; three phosphates distinguish ATP from ADP (two phosphates).

Why D is correct:

• ATP is defined as a ribonucleotide (adenine + ribose + phosphate) with three phosphate groups total, often described as having additional phosphates beyond the standard single-phosphate nucleotide.

Why the others are wrong:

• A: DNA nucleotides contain deoxyribose sugar, not ribose.
• B: DNA uses deoxyribose, and two phosphates describe ADP, not ATP.
• C: RNA is correct for ribose, but two phosphates describe ADP, not ATP.

Final answer: D