Biochemistry: Carbohydrates and Lipids

Introduction to Biochemistry
  • Biochemistry is conceptually similar to organic chemistry, focusing on carbon-based compounds.
  • The main focus will be on understanding compounds rather than mathematical aspects.
Key Sections in Biochemistry
  • Biochemistry can be divided into various units; however, today's focus is on carbohydrates and lipids.
  • Future discussions will involve proteins, enzymes, and amino acids in the following week.
Structure and Naming of Biomolecules
  • Unlike organic chemistry (naming and drawing compounds), the emphasis in biochemistry will be on:
    • Understanding the function of compounds
    • Recognizing structures of carbohydrates and lipids
Carbohydrates
  • Definition: Carbohydrates are carbon-based molecules that are structured such that for every carbon atom, there are typically:
    • 2 hydrogens
    • 1 oxygen
  • This structure resembles that of water (H2O), hence the name carbohydrate (carbons + hydrates).
  • Generalization: For every carbon in a carbohydrate, expect an equal number of water molecules or the ratio of 2 hydrogens and 1 oxygen.
Categories of Carbohydrates
  • Carbohydrates can be classified into saccharides:
    • Monosaccharides: Single sugar units (e.g., glucose).
    • Disaccharides: Two monosaccharides linked together.
    • Polysaccharides: Multiple monosaccharides linked together.
Monosaccharides
  • Examples include aldoses and ketoses:
    • Aldoses: Sugars with an aldehyde group (e.g., glucose).
    • Ketoses: Sugars with a ketone group (e.g., fructose).
  • Each type is characterized by its structure and the arrangement of hydroxides.
  • Dehydration Reaction: The process where monosaccharides link together:
    • Removal of water leads to the formation of glycosidic bonds (the bond formed between sugars).
Glycosidic Bonds
  • Definition: A bond formed between two monosaccharides resulting from a dehydration reaction.
  • Important in the formation of disaccharides and polysaccharides.
Reactions of Monosaccharides
  • Oxidation: Converts aldoses into carboxylic acids (sugar acids).
    • Example: Glucose oxidizes to form gluconic acid.
  • Reduction: Converts ketoses into sugar alcohols (e.g., converting fructose to a sugar alcohol).
Lipids
  • Definition: Lipids are primarily hydrophobic molecules consisting of long carbon chains, making them non-polar and water-resistant.
  • Common types of lipids:
    • Fatty Acids: Long unbranched carboxylic acids.
    • Can be saturated (no double bonds) or unsaturated (with double bonds).
    • Waxes: Formed from esterification reactions involving fatty acids and alcohols (biochemical equivalent of esters).
    • Triglycerides (or Triacylglycerols): Composed of three fatty acids linked to a glycerol molecule via ester bonds.
    • Phospholipids: Similar to triglycerides but one fatty acid is replaced with a phosphoester bond.
Summary Points
  • For carbohydrates:
    • Recognize the general structures of monosaccharides, disaccharides, and polysaccharides.
    • Understand the classification into aldoses and ketoses and their respective reactions.
  • For lipids:
    • Be able to identify fatty acids, waxes, triglycerides, and phospholipids based on their structures and characteristics.
  • The focus is on recognition and understanding rather than detailed naming or drawing. Next week will cover more functional aspects of these biomolecules.