Fats are built like polymers but aren't polymers
- The idea
- Predict
- See it
- Why
- Check
The idea
“Fats are built by dehydration synthesis, so they're polymers like starch.”
Fats, starch and proteins all form when pieces join and water comes off. Only some can keep adding pieces.
The short version
The mistake: Fats are built by dehydration synthesis, so they're polymers like starch.
What's actually true: A polymer is a chain of repeating monomers that can keep growing. A fat is glycerol plus three fatty acids, with a fixed size.
- A polymer is a chain of monomers joined by the same bond over and over, like starch, proteins and nucleic acids.
- Each monomer that joins brings a new open site, so a polymer can keep growing.
- Dehydration synthesis builds fats and polymers alike, so the reaction can't tell you what's a polymer.
On the exam: Ask whether the units repeat and the end stays open. A fat stops at three fatty acids.