Carbohydrates are structurally classified based on the number of sugar units they contain.
1. Monosaccharides (simple sugars)
- Single sugar unit.
- Cannot be hydrolyzed into simpler sugars.
- Examples: Glucose, Fructose, Galactose.
- Can be further classified by carbon atoms:
- Trioses (3C), Pentoses (5C), Hexoses (6C)
- Also by functional group:
- Aldoses (with aldehyde group), Ketoses (with ketone group)
2. Disaccharides
- Two monosaccharides linked by a glycosidic bond.
- Formed by condensation reaction (loss of water).
- Examples: Sucrose (glucose + fructose), Maltose (glucose + glucose), Lactose (glucose + galactose)
3. Oligosaccharides
- Contain 3–10 monosaccharide units.
- Often attached to proteins or lipids on cell surfaces for recognition.
- Examples: Raffinose, Stachyose
4. Polysaccharides (complex carbohydrates)
- Many monosaccharide units linked together.
- Can be linear or branched.
- Serve as energy storage or structural support.
- Examples:
- Energy storage: Starch (plants), Glycogen (animals)
- Structural: Cellulose (plants), Chitin (insects/fungi)
In short:
Carbohydrates are classified as monosaccharides, disaccharides, oligosaccharides, and polysaccharides based on the number of sugar units and their complexity.