Lecture on Carbohydrates

Introduction to Carbohydrates

• Definition: Carbohydrates are chemical compounds made up of carbon atoms that are fully hydrated (carbo = carbon, hydrate = water).
• General Formula: C_n(H2O)_n (n = number of carbon atoms).
• Ratio: 1:2:1 ratio of carbon, hydrogen, and oxygen._

Types of Carbohydrates

• Monosaccharides: Single carbohydrate molecules (simple sugars).
  • Derived from the Greek word for sugar, saccharide.
• Polysaccharides: Multiple carbohydrate molecules linked together (e.g., cellulose forms the structural backbone of plant cell walls).
• Notable monosaccharides include glucose and ribose.

Functionality of Carbohydrates

• Energy Source: Glucose is the main energy source for metabolism in the body.
• Structural Role: Cellulose provides structural rigidity in plant cell walls.
• Genetic Support: Ribose is a component of RNA, supporting genetic transcription.

Naming Conventions

• Suffix: -ose indicates a sugar (e.g., glucose, cellulose, ribose).
• Number of Carbons:
  • Tri = 3 (triose)
  • Tetra = 4 (tetrose)
  • Penta = 5 (pentose)
  • Hexa = 6 (hexose)

Examples

• Glyceraldehyde: A simple carbohydrate with three carbons (triose).
• Glucose: A six-carbon carbohydrate (hexose) with an aldehyde functional group (aldohexose).
• Fructose: Another six-carbon carbohydrate (hexose) but with a ketone functional group (ketohexose).

Functional Groups

• Aldehyde vs Ketone: Determines the second naming prefix.
  • Aldohexose (e.g., glucose has an aldehyde group).
  • Ketohexose (e.g., fructose has a ketone group).

Stereochemistry

• Fisher Projection: Used to determine the highest numbered chiral center.
  • R (Right) or D (Dexter) configuration: Hydroxyl group on the right.
  • L (Left) configuration: Hydroxyl group on the left.
• Examples:
  • D-Glucose: A D-aldohexose due to the right-side placement of the hydroxyl group.
  • D-Fructose: A D-ketohexose with the hydroxyl group on the right.

Additional Learning Resources

• Recommended video on Fisher projections from Khan Academy to better understand stereochemistry in carbohydrates.