Apentix/AP Biology/Unit 1: Chemistry of Life/Question
AP Biologymediummcq1 pt

Which structural feature reliably distinguishes RNA from DNA in a cell?

A.Ribose in RNA bears a hydroxyl on its second carbon, while deoxyribose in DNA has only a hydrogen there
B.DNA contains uracil wherever RNA would contain thymine
C.RNA lacks phosphate groups connecting its sugars
D.RNA bases contain nitrogen while DNA bases are built from carbon alone

Explanation

Core Concept

The name deoxyribose records the difference: DNA's sugar lacks the oxygen that RNA keeps on the 2' carbon. That extra RNA hydroxyl makes the backbone far more prone to chemical cleavage and lets RNA adopt catalytic folds, while DNA trades this reactivity for long-term stability. RNA additionally uses uracil instead of thymine and usually exists single stranded, but the sugar distinction applies to essentially every nucleotide in each polymer.

Correct Answer

ARibose in RNA bears a hydroxyl on its second carbon, while deoxyribose in DNA has only a hydrogen there

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