| 1.3 Introduction to Macromolecules |
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Summary
Biological macromolecules are polymers assembled from monomer subunits through dehydration synthesis, a reaction that removes water and forms a covalent bond between adjacent monomers. Repeating this reaction many times — polymerization — produces the large molecules cells need for structure, energy storage, and information.
Key Definition Hydrolysis consumes a water molecule to break the covalent bond between monomers, splitting the hydrogen ion onto one monomer and the hydroxyl group onto the other, thereby dismantling polymers into their building blocks. |
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Together, these two reactions form a reversible system that cells use to build up and break down macromolecules as needed.
Dehydration Synthesis
- Dominates during growth and biosynthesis
Hydrolysis
- Dominates during digestion and molecular recycling
Both reactions center on covalent bonds and water, but they operate in opposite directions — a symmetry that AP exam questions frequently test by asking students to compare the two side by side, specifying bond changes and the precise fate of the water molecule.