Carbohydrates §

• Organic
• Made up of carbon, hydrogen and oxygen
• Ususaly
• Ratio of hydrogen to oxygen is 2:1
• Provides energy for cellular activities
• Form supporting structures
• Form nucleic acids

Simple Sugars (monosaccharides) §

• Small molecules which cannot be further digested and can pass through plasma (cell surface) membrane
• All simple sugars are reducing sugars
• Eg: Glucose, Fructose, Galactose
• Looks like hexagon/pentagon

Structure:

Double Sugars (disaccharides) §

• Two monosaccharides are chemically bonded together to form disaccharides by a condensation reaction
• CANNOT PASS THROUGH PLASMA MEMBRANE
• Eg: Maltose, Lactose, Sucrose
• Maltose and Lactose are reducing sugars, Sucrose is non-reducing sugar
• Reactions:
  • Glucose + Glucose -> Maltose + Water
  • Glucose + Fructose -> Sucrose + Water
  • Glucose + Galactose -> Lactose + Water
  • + -> +
  • THESE REACTIONS CAN ALSO BE REVERSED
• A glycosidic/ether bond (C-O-C) is formed between two monosaccharides

Complex Sugars (polysaccharides) §

• Complex carbohydrates
• Many single sugars combined by condensation reactions
• Eg: Starch, glycogen, cellulose
  • made of many glucose molecules
• Linked differently
• Different structure = different properties

Starch §

• Branched macromolecules, making it compact
• Made of several thousand glucose molecules
• In long helix chains
• Function:
  • Store carbohydrates in plants
• Found in storage organs

Glycogen §

• Branched macromolecules, making it compact
• Made of many glucose molecules arranged in short helical chains with many branches
• Function
  • Stores carbohydrates in animals
  • Insoluble
  • Digested to glucose
• Stored in liver and muscles of animals

Cellulose §

• Unbranched macromolecules
• Cannot be easily digested
• Glucose molecules in long straight chains, giving them high tensile strength
• Present in cell walls of plants

Reducing Sugars §

• Gives electrons to other end
• Can be tested with Benedict’s Test