cell membrane structure and function

• Cell Membrane Structure and Function

  • To be able to describe how the structure of the cell membrane regulates the flow of materials into/out of the cell
• Selectively Permeable


  A characteristic of cell membranes that allows it to regulate the passage of molecules
• Cell membranes are not to be confused with semi-permeability
• Types of Molecular Movement

  • Diffusion
  • Passive Transport
  • Active Transport
• Some molecules may need "help" to get through the cell membrane, so require help from transport proteins

  1. Large molecules

  2. Charged molecules or ions (Na+ or Cl-)

  3. Molecules that may be traveling up their concentration gradient
• Cell membranes are selectively permeable, bilayered, and contain embedded proteins with different functions
• Active Transport involves

  Molecules passing through a protein to cross the membrane, movement of solutes against their concentration gradient, requiring energy in the form of ATP, and the use of proteins or "pumps" to transport molecules across the membrane
• Selective permeability depends on the structure of the membrane
• Cell membranes are "selective" due to

  1. Proteins embedded within membrane decide what can pass: big, small, necessary, unnecessary, charged, etc.

  2. Properties of the phospholipids that make up the layer: Nonpolar, hydrophobic
• Water, CO2, Glucose (C6H12O6), Starch, Potassium (K+), estrogen, Na+ are mentioned as molecules that may or may not be allowed through the lipid bilayer
• Anatomy of a Cell Membrane

  • Phospholipid
  • Hydrophilic
  • Hydrophobic
  • Polar
  • Nonpolar
  • Phosphate
  • Glycoprotein
  • Protein
• Passive Transport includes

  1. Simple diffusion

  2. Facilitated diffusion

  3. Osmosis
• Interchangeable terms for Cell Membrane

  • Phospholipid Bilayer
  • Lipid Bilayer
  • Plasma Membrane
  • Fluid Mosaic Model
• Homework due: Biozone 46 and 47