Which of the following molecules is most similar in structure to $ATP$?

• A. $NADH$
• B. Coenzyme $A$
• C. $FAD$
• D. $GTP$

Answer: (D)

Verified step by step guidance

1. Begin by understanding the structure of ATP (adenosine triphosphate). ATP consists of an adenine base, a ribose sugar, and three phosphate groups. This structure is crucial for its role in energy transfer within cells.
2. Next, examine the structure of GTP (guanosine triphosphate). GTP is similar to ATP in that it also contains a ribose sugar and three phosphate groups. The key difference is the nitrogenous base: GTP has guanine instead of adenine.
3. Compare the structures of NADH, Coenzyme A, and FAD to ATP. NADH is a coenzyme involved in redox reactions and has a nicotinamide base, which is structurally different from ATP. Coenzyme A contains a pantothenic acid unit and a thiol group, which are not similar to ATP's structure. FAD is a flavin adenine dinucleotide, which includes a riboflavin moiety, differing significantly from ATP's structure.
4. Identify the structural similarities between ATP and GTP. Both molecules have a similar backbone consisting of a ribose sugar and three phosphate groups, making them structurally analogous except for the nitrogenous base.
5. Conclude that GTP is the molecule most similar in structure to ATP due to the shared components of ribose and phosphate groups, despite the difference in the nitrogenous base.