Which of the following most accurately describes the ribose component of a nucleotide triphosphate?

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Quizplus · Accepted Answer

11ecba2d_0ea3_4bbc_a3bf_6bbfdc3beb48_MD0008_00 Nucleotide triphosphates (NTPs) consist of a nitrogenous base (adenine, guanine, cytosine, or uracil), a sugar (ribose), and a triphosphate. Ribose is a pentose (five-carbon sugar) that links to the nitrogenous base through a glycosidic bond. A phosphoester bond links the 5′ carbon of ribose to the triphosphate group. Carbohydrates can participate in glycosidic linkages only when in cyclic form (furanose or pyranose), so ribose must be cyclic in NTPs. In the furanose form, the 5′ hydroxyl group can readily participate in phosphoester bonds. Because the ribose in an NTP is a pentose in the furanose form, it is classified as a pentofuranose. (Choice B) In the pyranose form, the 5′ hydroxyl group of ribose becomes part of the ring structure and cannot participate in phosphoester bonds, so ribose cannot be in the pyranose form in NTPs. (Choices C and D) Ribose is a pentose (five carbons), not a hexose (six carbons). Educational objective: Ribonucleotide triphosphates contain a nitrogenous base, ribose, and a triphosphate group linked to the 5′ carbon of ribose. Ribose is a five-carbon sugar (pentose) that must adopt the furanose form to be incorporated into the nucleotide triphosphates. In this form, it can be classified as a pentofuranose.

Which of the Following Most Accurately Describes the Ribose Component