VIDEO: Overview of Carbohydrates as Macromolecules

Sep 24, 2024

Lecture Notes: Carbohydrates as Macromolecules

Introduction to Carbohydrates

  • Carbohydrates are macromolecules composed of carbon, hydrogen, and oxygen.
  • These elements typically present in a 1:2:1 ratio (e.g., glucose C6H12O6).

Levels of Carbohydrates

  1. Monosaccharides

    • Monomers/building blocks of carbohydrates.
    • Examples include glucose.
    • Structure: Long carbon chains with oxygen and hydrogen.
    • Classification by carbon chain length:
      • Triose (3 carbons)
      • Pentose (5 carbons)
      • Hexose (6 carbons)
    • Functional groups: Carbonyl groups (double-bonded carbon and oxygen).
      • Aldoses: Carbonyl group on terminal carbon.
      • Ketoses: Carbonyl group on internal carbon.
    • Structure Types: Linear and ring structures (ring form is more common in water).
    • Function: Primary fuel source for cellular reactions, stores energy in nonpolar covalent bonds.

  2. Disaccharides

    • Comprised of two monosaccharides bonded by a glycosidic bond (e.g., sucrose = glucose + fructose).
    • Formation involves dehydration synthesis; breaking involves hydrolysis.
    • Function: Transportable form of sugar that can be broken down for fuel.

  3. Polysaccharides

    • Large chains of monosaccharides.
    • Types: Starch, glycogen, cellulose, chitin.
    • Starch: Made of amylose and amylopectin, produced by plants. Used as energy storage.
    • Glycogen: Produced by animals, used for energy storage.
    • Cellulose: Plant structural polysaccharide, reinforces cell walls.
    • Chitin: Structural polysaccharide in animals (e.g., insect exoskeletons).
    • Structure: Starch and glycogen are helical and branched; cellulose and chitin are straight and reinforced.

Structure-Function Relationship

  • Starch and glycogen: Helical, easily broken for energy.
  • Cellulose and chitin: Straight chains with bonds for structural support.
  • Form fits function: Structure of polysaccharides matches their biological role.

Special Cases

  • Enzymatic Breakdown
    • Starch and glycogen can be broken down by enzymes in humans.
    • Cellulose and chitin require different enzymes, not produced by humans.
  • Some animals have bacteria that enable cellulose digestion.

Conclusion

  • Carbohydrates serve as crucial energy sources and structural components in organisms.
  • Understanding structure helps appreciate their diverse functions.