Read It Backwards, Get a Different Molecule

Topic 1.3 built the chains. This one asks what they are — and the answer is never the ingredient list. A biological polymer has two chemically different ends, so it runs one way and one way only: proteins from N to C, nucleic acids 5′ to 3′. Reverse the order and you have not respelled the same molecule; you have written a different one. Same trap, one level down: two sugars with one formula, two fats with one formula, doing opposite jobs. Structure is the molecule. The formula is only the receipt.

AP BIOLOGY · 8 STEPS · 6 QUICK CHECKS · PROTEINS N→C · NUCLEIC ACIDS 5′→3′ · SAME FORMULA ≠ SAME MOLECULE · v1