Disaccharides and Polysaccharides

Disaccharides

• Formed by joining two monosaccharide monomers.
• Occurs through a condensation reaction.
• A glycosidic bond is formed, releasing a water molecule.

Polysaccharides

• Comprised of many monosaccharides linked together.
• Examples include starch, glycogen, and cellulose.
• While all are composed of glucose, they differ in their bonding type.

Production of Macromolecules

• Monomers join together releasing water in a condensation reaction.
• This process is anabolic, requiring energy, usually ATP.

Digestion of Polymers

• Hydrolysis Reaction: Opposite of condensation. Breaks polymers into monomers.
  • Enzymes (e.g., sucrase) and water are used to break bonds and release monomers.
  • Digestion occurs in the digestive tract and by decomposers in the environment.

Polysaccharides: Starch, Glycogen, & Cellulose

• Starch: Energy storage in plants.

  • Consists of amylose and amylopectin.
    • Amylose: Unbranched chains (α 1-4 glycosidic bonds).
    • Amylopectin: Branched chains (α 1-6 glycosidic bonds).
  • Less soluble than glucose, preventing cell swelling by osmosis.

• Glycogen: Energy storage in animals.

  • Similar to amylopectin but with more 1-6 glycosidic bonds.
  • Mainly found in muscle and liver cells.
  • Insoluble in water, preventing osmotic swelling.

• Cellulose: Structural component.

  • Composed of β 1-4 linked glucose molecules.
  • Chains are straight and linked via hydrogen bonds forming microfibrils.
  • Provides strength and rigidity to plant cells, protecting against high pressure.

Energy Storage

• Starch in Plants:
  • Glucose can be removed from amylose and amylopectin for energy.
  • Question to consider: Which process is faster between amylose and amylopectin?
• Glycogen in Animals:
  • Serves as a quick energy source due to its branched nature which facilitates rapid glucose release.

Structural Role of Polysaccharides

• Cellulose forms a structural component in plant cells.
  • Provides tensile strength due to its microfibril formation.