Building a bond releases water. Breaking one uses it.
- The idea
- Predict
- See it
- Why
- Check
The idea
“Breaking a bond releases water, and forming one uses it up.”
Breaking a bond sounds like it should let water out. It runs the other way, and the two long names are easy to swap.
The short version
The mistake: Breaking a bond releases water, and forming one uses it up.
What's actually true: Dehydration synthesis builds a bond and releases one water. Hydrolysis breaks a bond and uses one water.
- Dehydration synthesis joins two monomers and releases one water. Dehydration means losing water.
- Hydrolysis breaks the bond. Hydro means water and lysis means splitting, so a water is split and used up.
- Linking 5 monomers makes 4 bonds and releases 4 waters. Breaking all 4 bonds uses 4 waters.
- Carbohydrates, proteins and nucleic acids are built and broken this way. So are fats, even though they aren't polymers.
On the exam: Dehydration builds a bond and gives off water. Hydrolysis uses water to break one.