AQA A-Level Biology 2025/6

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Nucleic acids are always double‑stranded, providing redundancy, while proteins exist only as single chains. Proteins are rapidly degraded by cellular proteases, whereas nucleic acids are immune to enzymatic breakdown. Proteins contain nitrogen in their amino acids, making them too reactive to store genetic information safely. Nucleic acids have a uniform backbone of phosphate‑sugar linkages that is chemically stable, whereas proteins have variable side‑chain chemistries that do not provide a consistent, durable information‑bearing structure.

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