Introduction to Proteins

Importance of Proteins

• Proteins are organic molecules found in all organisms.
• Composed of carbon, hydrogen, oxygen, and other elements.
• Play many important roles in the body:
  • Structural Role:
    • Build structures such as:
      • Muscles (muscle fibers)
      • Tendons (attach muscles to skeleton)
      • Bones

Metabolic Roles of Proteins

• Proteins have metabolic roles, especially as enzymes.
  • Enzymes:
    • Catalyze reactions involving substrates to produce products.
    • Numerous types of proteins facilitate reactions in cells and cell membranes.
• Transport Proteins:
  • Example: Hemoglobin (Hb) transports oxygen from lungs to tissues.

Chemical Structure of Proteins

• Like carbohydrates and lipids, proteins contain:
  • Carbon
  • Hydrogen
  • Oxygen
• Unique to proteins:
  • Include nitrogen, sulfur, and phosphorus.

Amino Acids: Building Blocks of Proteins

• Definition: Amino acids are monomers that combine to form proteins (polymers).
• Each amino acid has the same basic structure:
  • Components of an Amino Acid:
    • Central Carbon (C)
    • Carboxyl Group (COOH)
    • Amino Group (NH2)
    • Hydrogen Atom (H)
    • R Group (Variable Group)
• There are 20 naturally occurring amino acids, each with a unique R group.

Variability of R Groups

• R groups can differ in:
  • Size:
    • Example: Glycine (simple) vs. Lysine (complex).
  • Polarity:
    • Non-polar: Alanine (CH3)
    • Polar: Cysteine (contains sulfur and hydrogen).
  • Charge:
    • Basic Amino Acids:
      • Example: Lysine (positively charged).
    • Acidic Amino Acids:
      • Example: Aspartic acid (negatively charged).

Summary

• The diverse properties of the 20 amino acids allow for the formation of a wide variety of proteins with different functions and characteristics.