Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologyhardmcq1 pt

RNA is chemically less durable than DNA partly because their sugars differ. Which statement describes the decisive difference?

A.Ribose bears a hydroxyl group on its 2' carbon, enabling attacks that cleave the RNA backbone.
B.Ribose has no oxygen atoms, so the RNA backbone falls apart easily.
C.Ribose carries a phosphate group on every ring carbon, straining the chain.
D.Uracil is fused directly into the sugar ring instead of attaching to it.

Explanation

Core Concept

Deoxyribose lacks an oxygen at the 2' position, while ribose carries a hydroxyl group there. That RNA 2' hydroxyl can chemically attack the adjacent phosphodiester bond, especially in flexible single-stranded regions and under alkaline conditions, cutting the chain. Removing the 2' oxygen eliminates this internal route of degradation, so the same backbone architecture persists far longer in DNA. Durability explains why genomes are archived in DNA while RNA handles shorter-lived roles, and why some RNAs exploit that very reactivity for catalysis.

Correct Answer

ARibose bears a hydroxyl group on its 2' carbon, enabling attacks that cleave the RNA backbone.

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