Carbohydrates of Biological Importance

Chemical Nature of Carbohydrates

  • Carbohydrates are polyhydroxyalcohols with aldehyde or keto groups.

  • General formula: C<em>n(H</em>2O)nC<em>n(H</em>2O)_n

Biomedical Importance of Carbohydrates

  • Most abundant organic molecules in nature.

  • Functions include:

    • Major source of dietary calories.

    • Energy storage.

    • Cell membrane components aiding intercellular communication.

Classification of Carbohydrates

  • Main Types:

    • Monosaccharides

    • Disaccharides

    • Oligosaccharides

    • Polysaccharides

Monosaccharides

  • Simplest sugars classified by:

    • Number of carbons: Trioses (C3), Tetroses (C4), Pentoses (C5), Hexoses (C6).

    • Functional groups: Aldoses (with aldehyde) vs. Ketoses (with ketone).

Aldoses

  • Simplest aldohexose: D-Glucose.

  • D-sugars: Hydroxyl on right of penultimate carbon.

  • L-sugars: Hydroxyl on left of penultimate carbon.

Ketoses

  • Simplest ketose: Dihydroxyacetone (triose).

  • Subclassified into: Ketotrioses (C3), Ketotetroses (C4), Ketopentoses (C5), Ketohexoses (C6).

Isomerism in Monosaccharides

  • Same molecular formula, different structural or steric formulas.

  • Types of isomerism:

    1. Optical isomers (D and L-sugars)

    2. Anomers

    3. Epimers

    4. Aldose-Ketose isomers.