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Overview of Carbohydrates

  • D-Glucose
    • Type: Aldose
    • Structural features: Contains 4 chiral carbons
    • Significance: Energy source, energy storage, and structural role in plants

Types of Monosaccharides

Aldoses
  • Key Aldoses:
    • D-Glyceraldehyde
    • D-Erythrose
    • D-Threose
    • D-Ribose
    • D-Arabinose
    • D-Xylose
    • D-Lyxose
    • D-Allose
    • D-Mannose
    • D-Galactose
    • D-Talose
    • D-Altrose
Ketoses
  • Key Ketoses:
    • Dihydroxyacetone
    • D-Erythrulose
    • D-Ribulose
    • D-Xylulose
    • D-Psicose
    • D-Fructose
    • D-Sorbose
    • D-Tagatose

D and L Configurations

  • D and L Notation: Indicates the configuration of the farthest chiral carbon from the carbonyl group.
  • Mostly D-monosaccharides are observed in nature.
  • D and L forms are enantiomers.
    • Example: D (+)-Glucose rotates to the right, while D (-)-Fructose rotates to the left.

Epimers

  • Definition: Epimers differ in the configuration at one specific chiral center.
    • Example:
    • D-Mannose (epimer at C-2)
    • D-Galactose (epimer at C-4)
    • D-Glucose as the base reference.

Cyclization of Monosaccharides

  • Monosaccharides can form cyclic structures in aqueous solutions, leading to an additional chiral center.
  • Anomeric Carbon: The carbonyl carbon that becomes chiral during cyclization.
  • Anomers: Two configurations (α and β) around the anomeric carbon with distinct physical properties.
  • Mutarotation: The change in optical rotation as alpha and beta forms interconvert.

Monosaccharide Derivatives

  • Types:
    • Sugar acids: Aldonic and uronic acids.
    • Sugar alcohols: Formed by reduction (e.g., Sorbitol).
    • Deoxy sugars: One hydroxyl group replaced by hydrogen.
    • Amino sugars: Hydroxyl group replaced by an amino group (e.g., D-Glucosamine).
    • Glycosides: Formed via the reaction of the anomeric hydroxyl group with another compound.

Polysaccharides

  • Types:
    • Disaccharides: Two monosaccharides linked by glycosidic bonds.
    • Storage Polysaccharides: Such as starch and glycogen.
    • Starch: Mixture of amylose and amylopectin.
      • Amylose: Linear polymer linked through α(1-4) bonds.
      • Amylopectin: Branched polymer with mostly α(1-4) bonds and some α(1-6) branch points.
    • Glycogen: Similar to amylopectin but with more branch points.

Disaccharides and Their Characteristics

  • Lactose:

    • Constituted by galactose (C1 in β-configuration) linked to glucose (C4).
    • Classified as a reducing sugar.

  • Sucrose:

    • Formed by glucose (C1 in α-configuration) linked to fructose (C2 in β-configuration).
    • Non-reducing sugar.