Principle of Osmosis and Diffusion Basics

Principle of Osmosis and Diffusion

• Osmosis: Movement of water across membranes from high to low concentration.
  • Passive process.
  • Dynamic equilibrium.
  • Fast over short distances.
  • Dependent on temperature, concentration gradient, and particle size.
• Diffusion: Movement of particles across membranes from high to low concentration.
  • Passive process.
  • Dynamic equilibrium.
  • Fast over short distances.
  • Dependent on temperature, concentration gradient, and particle size.

Terms and Measures of Fluid and Electrolytes

• Molarity: Concentration of a purified compound in a volume of water (mol/L).
• Millimolar (mM): 1/1000 of a mole.
• Osmolality: The quantity of dissolved particulate matter in the water portion of plasma.
  • Measured in milliosmoles (mOsm).
  • Range: 270-290 mOsm (average: 286 mOsm).
• Equivalents: Reflects the ion charge in a solution.
  • Measured in milliequivalents (mEq/L).
  • Used for individual ions in cell membranes and protein structures.

Cell Membranes: "The Fluid Mosaic Model"

• Composed of phospholipids.
  • Hydrophilic head: Attracts water.
  • Hydrophobic tail: Repels water.
• Membrane structure: phospholipid bilayer.
• Fluid Mosaic Model:
  • Dynamic, moving phospholipids.
  • "No Flip Flop": Phospholipids move within their own bilayer.
  • Cholesterol helps maintain membrane fluidity.
  • Unsaturated fatty acids increase membrane fluidity.

Protein Structures in the Membranes

• 2 Major Categories:
  • Extrinsic, Peripheral, Associated Proteins:
    • Located on the surface of the membrane.
    • Examples: Structural proteins.
  • Intrinsic, Transmembrane, Integral Proteins:
    • Extend through the membrane.
    • Categories:
      • Structural:
        • Tight Junctions: Found in skin, small intestine, and blood-brain barrier (BBB).
        • Gap Junctions: Found in cardiac cells.
      • Enzymes
      • Receptors
      • Transporter Proteins:
        • Channels: Allow passive movement of molecules across the membrane.
          • Open Pore Channels: No gates or barriers.
          • Gated Channels: Open and close in response to stimuli.
            • Voltage-Gated Channels (VGC's): Open in response to changes in electrical potential.
        • Carriers: Bind to molecules and transport them across the membrane.
          • Require energy for transport.
      • Carrier Proteins: Bind to and move molecules across the membrane.
        • Require energy for transport.