Nomenclature of carbohydrates

Definition of Carbohydrates

Carbohydrates are organic compounds composed of carbon (C), hydrogen (H), and oxygen (O), typically in the ratio of 1:2:1, with the general formula $C_{n} (H_{2} O)_{n}$ . They are one of the primary macronutrients and serve as a major energy source for living organisms. Carbohydrates are classified based on their complexity and the number of sugar units they contain.

Nomenclature of Carbohydrates

Carbohydrates can be classified and named based on the number of sugar (saccharide) units they contain:

Monosaccharides:
- Definition: The simplest form of carbohydrates, consisting of a single sugar unit. They cannot be hydrolyzed into simpler sugars.
- Nomenclature: Named based on the number of carbon atoms and the functional group present (aldehyde or ketone).
  - Example:
    - Glucose: An aldohexose (six-carbon sugar with an aldehyde group), with the chemical formula $C_{6} H_{12} O_{6}$ .
    - Fructose: A ketohexose (six-carbon sugar with a ketone group), also with the chemical formula $C_{6} H_{12} O_{6}$ .
Disaccharides:
- Definition: Carbohydrates composed of two monosaccharide units linked by a glycosidic bond.
- Nomenclature: Named based on the monosaccharides involved and the type of glycosidic bond.
  - Example:
    - Sucrose: Composed of glucose and fructose linked by an α(1→2) glycosidic bond, with the chemical formula $C_{12} H_{22} O_{11}$ .
    - Lactose: Composed of glucose and galactose linked by a β(1→4) glycosidic bond, with the chemical formula $C_{12} H_{22} O_{11}$ .
Oligosaccharides:
- Definition: Carbohydrates composed of 3 to 10 monosaccharide units.
- Nomenclature: Typically named based on the number of monosaccharide units and the monosaccharides involved.
  - Example:
    - Raffinose: A trisaccharide composed of galactose, glucose, and fructose, with the chemical formula $C_{18} H_{32} O_{16}$ .
    - Stachyose: A tetrasaccharide composed of two galactose units, one glucose, and one fructose, with the chemical formula $C_{24} H_{42} O_{21}$ .
Polysaccharides:
- Definition: Carbohydrates composed of more than ten monosaccharide units. They can be linear or branched.
- Nomenclature: Named based on the type of monosaccharides, the glycosidic linkages, and their biological function.
  - Example:
    - Starch: A storage polysaccharide in plants, composed of amylose (linear) and amylopectin (branched) chains of glucose.
    - Cellulose: A structural polysaccharide in plant cell walls, composed of linear chains of glucose linked by β(1→4) glycosidic bonds.
    - Glycogen: A storage polysaccharide in animals, similar to amylopectin but more highly branched.