1. Cell Transport Osmosis and Diffusion

2.  Particles in constant motion  Run into each other and randomly spread out  Particles move from an area of high concentration to an area of low concentration Diffusion

3.  Can occur across membranes IF the particle can cross the membrane  Does not require energy  Passive transport Time Semipermeable

4. Facilitated Diffusion  Molecules that can’t pass directly through membrane may pass through a protein channel in membrane  Still no energy = passive transport

5. Osmosis  Specific type of facilitated diffusion  Diffusion of water through a selectively permeable membrane  Is energy required?

6. Osmosis, cont’d  Water moves from an area of high concentration to an area of low concentration.  When comparing two solutions:  Hypotonic – “below strength”; lower concentration of solute, higher concentration of water  Hypertonic – “above strength”; higher concentration of solute, lower concentration of water  Isotonic – “same strength”; solutions have same concentration of solute and same concentration of water

7. Osmosis, cont’d  Water moves from an area of high concentration to an area of low concentration. 1 % salt 99% water 0% salt 100% water In which direction will water move? Into the cell our out of the cell? Water moves into cell (trying to reach equilibrium) What will happen to the cell? Is the solution hypertonic, isotonic, or hypotonic? Hypotonic Solution

8. Osmosis, cont’d  Water moves from an area of high concentration to an area of low concentration. 1 % salt 99% water 5% salt 95% water In which direction will water move? Into the cell our out of the cell? Water moves out of the cell. What will happen to the cell? Is the solution hypertonic, isotonic, or hypotonic? Hypertonic Solution

9. Osmosis, cont’d  Water moves from an area of high concentration to an area of low concentration. 1 % salt 99% water 1% salt 99% water In which direction will water move? Into the cell our out of the cell? No net movement of water! What will happen to the cell? Is the solution hypertonic, isotonic, or hypotonic? Isotonic Solution

11. Active Transport  Allows movement of particles against the concentration gradient  In other words, particles can move from low concentration to high concentration  Proteins in membrane “pump” the molecules in or out  Requires energy  Active transport

12. Passive vs. Active Transport