| 1.4 Carbohydrates |
|---|
Summary
Carbohydrates are built from monosaccharide monomers joined by covalent bonds (glycosidic linkages) through dehydration synthesis. The resulting polysaccharides can be linear or branched, and this structural difference is what determines biological function.
Key Definition Hydrolysis reverses the process, breaking polymers back into monomers by adding water.
These same principles of monomer assembly and disassembly apply to every class of biological macromolecule.
Three key polysaccharides illustrate the structure–function relationship.
Starch
- Stores energy in plants
- Made of α-glucose; consists of amylose (unbranched, coiled) and amylopectin (branched)
Glycogen
- Stores energy in animals
- Extensive branching enabling rapid glucose release
Cellulose
- Forms rigid linear chains that provide structural support in plant cell walls
- Made of β-glucose; chains held together by hydrogen bonds to form microfibrils
At a Glance
| Polysaccharide | Role | Structure | Location |
|---|---|---|---|
| Starch | Stores energy | Coiled, helical chains; mix of unbranched (amylose) and branched (amylopectin) | Plants |
| Glycogen | Stores energy | Extensive branching enabling rapid glucose release | Animals |
| Cellulose | Structural support | Rigid linear chains | Plant cell walls |
Recognizing that all three polymers are composed of the same glucose monomer — yet serve fundamentally different roles — reinforces the central idea that molecular shape and bonding pattern drive biological function.