Carbohydrates Overview

Carbohydrates

• Organic compounds containing carbon, hydrogen, and oxygen.
• Ratio of hydrogen to oxygen is the same as in water.

Biochemical Importance

• Primary energy source for the body.
• Stored as glycogen in muscles and liver for later use.
• Cellulose, a component of fiber, promotes intestinal motility and waste elimination.
• Combine with lipids (glycolipids) and proteins (glycoproteins) to form structural components of cells.
• Food sources provide water-soluble vitamins and minerals

Classification:

• Monosaccharides: Single sugar unit, simplest carbohydrates
• Oligosaccharides: 2-10 sugar units
• Polysaccharides: More than 10 sugar units

Monosaccharides

• Simplest carbohydrates with one sugar unit.
• Classified by the number of carbon atoms:
  • Trioses: 3 carbon atoms
  • Tetroses: 4 carbon atoms
  • Pentoses: 5 carbon atoms
  • Hexoses: 6 carbon atoms, e.g., glucose, fructose, galactose, and mannose.

Hexoses

• Glucose: Grape sugar, blood sugar, primary energy source for tissues. Stored as glycogen.
• Fructose: Found in fruit juices and honey, fetal blood, and seminal fluid.
• Galactose: Component of lactose (milk sugar), paired with glucose.
• Mannose: Found in mucoproteins.

Oligosaccharides

• Formed by condensation of 2 to 10 monosaccharide molecules.
• Disaccharides are the most important group.

Disaccharides

• Formated by condensation of 2 monosaccharides:
  • Lactose (Milk Sugar): 1 Galactose + 1 Glucose
  • Sucrose (Cane Sugar, Beet Sugar, Table Sugar): 1 Glucose + 1 Fructose
  • Maltose (Produced during Starch Digestion): 1 Glucose + 1 Glucose

Polysaccharides

• Composed of many monosaccharide units (more than 10) linked together.
• Homopolysaccharides: Contain only one type of sugar, e.g., starch, glycogen, cellulose, dextrins, dextrans, and agar-agar.
• Heteropolysaccharides: Contain different types of sugars, e.g., gums, pectin, and mucopolysaccharides.

Homopolysaccharides

• Contain similar sugar units
• Starch:
  • Major carbohydrate in food.
  • Primary storage form of carbohydrates in plants.
  • Found in cereals (rice, barley, maize, wheat) and roots and tubers (potatoes, sweet potatoes).
  • Not found in animals.
  • Granule structure:
    • Amylose: Inner layer, straight chain of glucose units.
    • Amylopectin: Outer layer, branched chains of glucose units.

Starch Structure

• Starch granules are formed of amylose and amylopectin.
• Amylose forms the inner layer and is made of straight chains of glucose units.
• Amylopectin forms the outer layer and is composed of branched chains of glucose units.