mbbs ims msu


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mbbs ims msu

  1. 1. Diffusion Summary <ul><li>Diffusion is the movement of molecule from one location to another by random thermal motion </li></ul><ul><li>The net flux between the two compartments always proceed from higher to lower concentration </li></ul><ul><li>Diffusion equilibirum is reached when the two concentration become equal </li></ul>
  2. 2. Osmosis Summary <ul><li>Water crosses membranes by diffusing through protein channels in the membrane </li></ul><ul><li>Osmosis is the diffusion of water from higher water concentration to lower water concentration. Osmolarity total solute concentration in the solution. The higher osmolarity of a solution the lower the water concentration. </li></ul>
  3. 3. <ul><li>Osmosis across membrane permeable to water but impermeable to solute leads to increase volume in the compartment that initially had higher osmolarity. </li></ul><ul><li>Application to a solution of sufficient pressure will prevent the osmotic flow of water into the solution from the compartment of pure water. This pressure is osmotic pressure. </li></ul><ul><li>The greater the osmolarity of a solution the greater the osmotic pressure </li></ul>Osmosis Summary
  4. 4. <ul><li>The osmolarity of the extracellular fluid is about 300 mOsm. Intracellular fluid has osmolarity equal to that of extracellular fluid </li></ul><ul><li>Na and Cl ions are major effectively nonpenetrating solutes in the extracellular fluids. K ions and various organic solute are nonpenetrating solute in the intracellular fluid </li></ul>Osmosis Summary
  5. 5. Endocytosis and Exocytosis <ul><li>During endocytosis vesicles will be formed that enclose a small volume of extracellular material </li></ul><ul><li>Three classes of endocytosis (1) fluid endocytosis (2) adsorptive endocytosis and (3) phagocytosis </li></ul><ul><li>Vesicles content digested by lysosome enzyme </li></ul><ul><li>Exocytosis provide a means of adding components to the plasma membrane and a route to release impermeable molecules into extracellular fluid </li></ul>
  6. 6. Mediated Transport System <ul><li>Involve binding of the transported solute to transporter protein in the membrane. Changes in the conformation of the transporter move the binding site to the opposite side of the membrane </li></ul><ul><li>The binding sites exhibit chemical specificity and saturation </li></ul>
  7. 7. <ul><li>Facilitated diffusion move molecule from higher to lower concentration across the membrane by means of transporter. Metabolic energy is not required. </li></ul><ul><li>Active transport moves molecules against an electrochemical gradient across a membrane by means of transporter and require energy </li></ul>Mediated Transport System
  8. 8. <ul><li>Primary active transport uses the phosphorylation of the transporter by ATP to drive the transport process </li></ul><ul><li>Secondary active transport uses the binding of ions (often Na) to the transporter to drive the transport process </li></ul><ul><li>In secondary active transport the downhill flow of an ion is linked to the uphill movement of a second solute either in the same direction as the ion (cotransport) or opposite direction of the ion (countertransport) </li></ul>Mediated Transport System
  9. 9. Epithelial Transport <ul><li>Molecules can cross epithelial layer by (1) through the extracellular spaces between the cells (paracellular pathway) and (2) through the cell across both luminal and basolateral membrane </li></ul><ul><li>The permeability and transport characteristics of the luminal and basolateral plasma membrane differ, resulting in the ability of the cells to actively transport a substance between the fluid on one side of the cell and the fluid on the opposite side of the cell </li></ul>
  10. 10. <ul><li>Major chemical substance in extracellular fluid are Na and Cl. Intracellular contain high K and negatively charged proteins and phosphate compound </li></ul><ul><li>Electrical resulting from this distribution have a significant role in cell integration and communication </li></ul>Membrane Potentials
  11. 11. <ul><li>Potential difference determine the difference in the amount of charge between two points. </li></ul><ul><li>The movement of electric charge is called current </li></ul><ul><li>The current depends on the potential difference between the charges </li></ul>Membrane Potentials
  12. 12. Terms describing the membrane potential <ul><li>Potential – Potential difference: The difference between two points </li></ul><ul><li>Membrane potential: The voltage between inside and outside the cell </li></ul><ul><li>Resting potential: The steady membrane potential of a cell that is not producing an electric signal </li></ul>
  13. 13. Ion Distribution <ul><li>Particles / molecules </li></ul><ul><ul><li>electrically charged </li></ul></ul><ul><li>Anions </li></ul><ul><ul><li>negatively charged </li></ul></ul><ul><li>Cations </li></ul><ul><ul><li>positively charged </li></ul></ul>
  14. 14. <ul><li>Anions (-) </li></ul><ul><ul><li>Large intracellular proteins </li></ul></ul><ul><ul><li>Chloride ions Cl- </li></ul></ul><ul><li>Cations (+) </li></ul><ul><ul><li>Sodium Na+ </li></ul></ul><ul><ul><li>Potassium K+ </li></ul></ul>Ion Distribution
  15. 15. The resting Membrane Potential <ul><li>All cells have potential difference, inside negatively charged with respect to the outside. This potential is the resting membrane potential </li></ul>
  16. 16. Role of Electric Forces on Ion Movement <ul><li>Separation of electric charge across plasma membranes known as Membrane Potential </li></ul><ul><li>Membrane Potential provides an electric force that influences the movement of ions across the membrane. </li></ul>
  17. 17. Resting Membrane Potential <ul><li>The magnitude of the resting membrane potential determined by two factors: </li></ul><ul><li>Differences in specific ion concentration in the intracellular and extracellular fluids </li></ul><ul><li>Differences in the membrane permeabilities to the different ions </li></ul>
  18. 18. <ul><li>Plasma membrane Na, K- ATPase pumps maintain intracellular Na concentration low and K high </li></ul><ul><li>In almost all resting cells, the plasma membrane is much more permeable to K than to Na </li></ul>Resting Membrane Potential
  19. 19. Electrochemical Gradient <ul><li>The Direction and Magnitude of ion fluxes across membranes depend on both the concentration difference and the electrical difference. </li></ul><ul><li>These two forces are collectively known as the electrochemical gradient . </li></ul>
  20. 20. Graded Potentials and Action Potentials <ul><li>Changes in the membrane potential from its resting level produce electric signals </li></ul><ul><li>These signals occur in two forms: graded potentials and action potentials </li></ul><ul><li>Graded signaling over short distance while action potentials are long distance signals of nerve and muscle membrane </li></ul>