Cell and Tissue Biology Lecture 2, Part A

Cell and Tissue Biology (Lecture 2, Part A)

• Lecture covers biological membranes and extracellular matrix (ECM)
• Contents: Explores fats (lipids), molecules in the natural world (proteins, amino acids, DNA), biological membranes, ECM, and cell adhesion.
• Phospholipids: Essential components of cell membranes.
  • Similar to triglycerides
  • Formed by condensation reactions
  • Contain only two fatty acid chains.
  • A "head" group substitutes the third fatty acid, containing phosphorus and nitrogen
  • Polar head (hydrophilic): Attracted to water
  • Non-polar tail (hydrophobic): Repelled by water
• Phospholipid structure: The phospholipid molecule has a polar head and non-polar tail
  • This structural feature results in an amphipathic nature of the molecule meaning it has both hydrophilic and hydrophobic properties
• Amphipathic nature: The combined hydrophobic and hydrophilic properties enable phospholipids (and other lipids) to organize into membranes. These properties ensure the phospholipids arrange so that the polar heads face the water (water-soluble) and the non-polar tails face away from water (water-insoluble).
• Phospholipid bilayer: A fundamental structure of cell membranes.
  • Forms a bilayer with hydrophilic heads facing the aqueous environments (inside and outside of the cell) and hydrophobic tails facing each other in the middle.
• Phospholipid structures: Under certain conditions, phospholipids can form various structures.
  • Micelles: Single phospholipid layer, typically formed in solution
  • Liposomes: Double phospholipid layer forming a closed sphere. Often used for drug delivery.
• Steroids: Large lipid molecules containing four interconnected carbon rings.
  • Cholesterol: The best-known steroid, found in all cell membranes
  • Cholesterol plays a role in regulating membrane fluidity and is a precursor to some steroid hormones (sex hormones).
  • Sources of cholesterol include diet and the liver can synthesize large amounts
• Fatty Acids: Essential components of lipids.
  • Provide energy and structural support in the body
  • Essential for cellular function
• Amino Acids and Proteins: Proteins are a vital part of the human body.
  • Consists of a central carbon atom (C) bonded to an amino group, a carboxyl group, a hydrogen atom, and an R-group or side chain.
  • Make up about 20% of the human body's weight.
  • Composed of amino acids
  • Functions: Support, movement, transport. buffering. metabolic regulation, coordination and control, defense.
• Protein Structure:
  • Proteins are long chains of amino acids (AA)
  • AA are joined together by peptide bonds to form polypeptide chains
  • 20 different types of AA
  • Individual AA differing in R-group/side chain
  • Chains form various configurations, determining function.
  • Globular proteins (such as hemoglobin and myoglobin have specific roles)
  • Fibrous proteins (such as keratin have structural roles)

This lecture delves into biological membranes and the extracellular matrix, focusing on phospholipids and their unique structure. Key topics include the properties of lipids, proteins, and the significance of cell adhesion in biological systems. Ideal for students seeking to understand the complex interactions within cells.