Not every sugar difference is alpha versus beta
- The idea
- Predict
- See it
- Why
- Check
The idea
“When two carbohydrates behave differently, one has alpha linkages and the other beta.”
Starch versus cellulose is the contrast you've drilled most, so it comes to mind first. Many differences have other causes.
The short version
The mistake: When two carbohydrates behave differently, one has alpha linkages and the other beta.
What's actually true: Alpha versus beta explains starch versus cellulose. Other differences come from monomers, branching, or how chains pack.
- A glycosidic linkage joins two sugars. It's alpha in starch and beta in cellulose, which changes the chain's shape and which enzymes fit.
- Carbohydrates also differ in their monomers, their branching, and how tightly their chains pack.
- First check what the two molecules share. If their linkages match, look elsewhere.
On the exam: Before you answer alpha versus beta, check that the linkages differ.