Starch, glycogen, cellulose and chitin do different jobs
- The idea
- Predict
- See it
- Why
- Check
The idea
“They're all glucose chains, so any of them can store fuel, in plants and animals alike.”
All four are chains of nearly the same sugar, so the names feel interchangeable. Each one has its own job.
The short version
The mistake: They're all glucose chains, so any of them can store fuel, in plants and animals alike.
What's actually true: Plants store starch, animals and fungi store glycogen, and cellulose and chitin build walls and shells.
- Starch, glycogen and cellulose are glucose chains. Chitin's units are glucose with a nitrogen group added. How the units link sets each one's job.
- Starch and glycogen use alpha linkages and coil into compact shapes. Enzymes cut these easily, so glucose comes out fast. Glycogen branches the most.
- Cellulose and chitin use beta linkages. Their straight chains hydrogen bond into tough fibers. We have no enzyme for cellulose's beta linkages.
On the exam: Plants store starch and build cellulose. Animals and fungi store glycogen. Fungi and arthropods build chitin.