1. Membrane Function and Cell Communication

2. Summary How do materials get across a cell's membrane? How do materials get across a cell's membrane? It depends on the type of substance It depends on the type of substance

3. Summary Non-polar materials or hydrophobic materials do cross easily, especially if small. Ex – CO 2, O 2 Non-polar materials or hydrophobic materials do cross easily, especially if small. Ex – CO 2, O 2 Phospholipid bilayer is MOSTLY hydrophobic (non-polar), so hydrophilic (polar) materials don't cross easily. (ions, water soluble, polar molecules etc.) Phospholipid bilayer is MOSTLY hydrophobic (non-polar), so hydrophilic (polar) materials don't cross easily. (ions, water soluble, polar molecules etc.) Large molecules don't cross easily. Too big to get through the membrane. Large molecules don't cross easily. Too big to get through the membrane.

4. Rank the relative rates from SLOWEST to FASTEST at which the particles cross the cell membrane through diffusion Rank the relative rates from SLOWEST to FASTEST at which the particles cross the cell membrane through diffusion A. Sodium ion < glucose < water < oxygen A. Sodium ion < glucose < water < oxygen B. Sodium ion < water < glucose < oxygen B. Sodium ion < water < glucose < oxygen C. Oxygen < glucose < water < sodium ion C. Oxygen < glucose < water < sodium ion A. sodium is an ion so doesn’t cross. Glucose and water are both polar, but glucose is larger than water so it diffuses slower than water. Oxygen is nonpolar so it diffuses quickly A. sodium is an ion so doesn’t cross. Glucose and water are both polar, but glucose is larger than water so it diffuses slower than water. Oxygen is nonpolar so it diffuses quickly

5. Membrane Function Review When urea moves through embedded proteins from the inside of a cell (high concentration) to the outside of a cell (low concentration) the process is called When urea moves through embedded proteins from the inside of a cell (high concentration) to the outside of a cell (low concentration) the process is called A. urination A. urination B. diffusion B. diffusion C. facilitated diffusion C. facilitated diffusion D. active transport D. active transport C facilitated diffusion

6. Membrane Function Review Explain why an embedded protein is used to move glucose molecules across a membrane. Explain why an embedded protein is used to move glucose molecules across a membrane.

7. Membrane Function Review Glucose is a large polar molecule. It does not travel well through the phospholipid bilayer due to the nonpolar nature of the center of the membrane. An embedded protein provides the glucose molecule with a path that is more polar and allows the larger molecule to move through freely. Glucose is a large polar molecule. It does not travel well through the phospholipid bilayer due to the nonpolar nature of the center of the membrane. An embedded protein provides the glucose molecule with a path that is more polar and allows the larger molecule to move through freely.

8. Stages of C.S. 1. Reception - receiving the signal. 2. Transduction - passing on the signal. 3. Response - cellular changes because of the signal.

9. Reception

10. Transduction

11. Response

13. Reception The target cell’s detection of a signal coming from outside the cell. The target cell’s detection of a signal coming from outside the cell. May occur by: May occur by: Direct Contact Direct Contact Through signal molecules Through signal molecules

14. Direct Contact When molecules can flow directly from cell to cell without crossing membranes. When molecules can flow directly from cell to cell without crossing membranes. Plants - plasmodesmata Plants - plasmodesmata Animals - gap junctions Animals - gap junctions

16. Direct Contact May also occur by cell surface molecules that project from the surface and “touch” another cell. May also occur by cell surface molecules that project from the surface and “touch” another cell.