Understanding Proteins and Amino Acids

Aug 30, 2024

Lecture on Proteins and Amino Acids

Structure and Function of Proteins

  • Proteins are three-dimensional coiled chains of amino acids.
    • Amino acid chain: polypeptide
    • Functional when coiled as proteins
  • Denaturation: process that uncoils proteins into polypeptide chains, causing them to lose functionality. Caused by:
    • High temperature
    • Acidosis or alkalosis
    • Exposure to heavy metals

Amino Acids

  • Structure: Carbon atom bonded to:
    • Amino group
    • Carboxylic acid group
    • Hydrogen atom
    • Variable group (R group) – varies among different amino acids
  • Types: 20 different amino acids
    • Example amino acids: Glycine, Leucine, Phenylalanine, Lysine, Cysteine

Amino Acid Linking Reactions

  • Dehydration synthesis: Joins amino acids into polypeptides
  • Hydrolysis: Splits polypeptide chains into individual amino acids

Essential vs Non-Essential Amino Acids

  • 20 types needed to construct proteins
  • Essential amino acids: Must be obtained from diet, e.g., Phenylalanine
  • Non-essential amino acids: Can be synthesized by the body, e.g., Tyrosine

Dietary Sources

  • Complete proteins: Contain all essential amino acids (e.g., eggs, most meats)
  • Incomplete proteins: Lack some essential amino acids (e.g., plant proteins like beans and rice)

Protein Diversity

  • Proteins differ by:
    1. Number of amino acids
    2. Types of amino acids
    3. Sequence of amino acids
    4. Three-dimensional structure

Types of Proteins

  • Enzymes: Catalyze biochemical reactions essential for life
    • Specific to substrates, akin to a "lock and key" model
  • Enzyme Inhibitors: Stop enzyme function, some act as poisons (e.g., cyanide)
    • Used in antibiotics to target bacterial enzymes
    • Aspirin, Advil inhibit enzymes forming prostaglandins
    • Statins inhibit enzymes converting fatty acids to cholesterol

Hormones

  • Steroid vs Protein Hormones:
    • Steroid hormones are absorbed directly (e.g., birth control pills)
    • Protein hormones must be injected (e.g., insulin, growth hormone)

Examples of Protein Hormones

  • Insulin: Lowers blood sugar levels
  • Growth Hormone: Produced by the pituitary gland
  • Oxytocin: Induces labor contractions

Other Protein Functions

  • Antibodies: Y-shaped proteins produced by B lymphocytes, inactivate foreign agents
  • Globular proteins: Examples include hemoglobin, immunoglobulin