1. Cell Boundaries
The Cell Membrane

2. The Cell Membrane Thin, flexible barrier
Regulates what enters and leaves
Protects and supports

3. aka: Phospholipid Bilayer.
Consists of:
hydrophilic head (water liking)
and a
hydrophobic tail.
(water avoiding)

4. Phospholipid Bilayer: Fluid Mosaic Model
Also has
Proteins – doorways
Carbohydrates – name tags
Cholesterol – keeps membrane flexible
Therefore referred to as a “fluid mosaic” of different molecules.

5. Assignment
Draw and label Figure 6 from page 188. Black and white okay. Do this in your journal. You will see a similar diagram on your test.
Complete the Cells Practice worksheet

6. Other Components and Functions
Proteins and carbohydrate chains
Protein channels/pores
Protein “pumps” or “carrier proteins”
Cholesterol
Act like “chemical id cards” so same cells can ID each other.
Allow some molecules to pass in or out without using energy.
Use energy to admit or send charged or larger molecules across the membrane.
Provides structure.

7. The Function of the Plasma Membrane
Cell Boundaries
The Function of the Plasma Membrane

8. The Cell Membrane Cells want nutrients Cells get rid of wastes
Two ways:
Passive Transport – No Cell Energy (ATP) needed
Active Transport – Cell Energy (ATP) required

9. Passive Transport - Diffusion
Molecules move from high to low concentration (with the “concentration gradient”) until “dynamic equilibrium” is reached.
Simple diffusion – small particles move between phospholipids of membrane
Facilitated diffusion – large particles move through transport proteins

10. Passive Transport - Diffusion

11. Passive Transport – Facilitated Diffusion

12. Passive Transport - Osmosis
The diffusion of water molecules through a cell membrane.
Concentration gradient depends on amount of dissolved particles (like salt) inside and outside the cell.

13. Isotonic Solution
Concentration of a dissolved substance (solute) is the same inside and outside the cell.
Isotonic = Dynamic equilibrium.
Cell stays same size.

14. Isotonic Solution

15. Hypotonic Solution
Concentration of the solute is low outside the cell and higher inside the cell.
Water moves INTO the cell.
Cell gets BIG like the O in hypOtonic

16. Hypotonic Solution

17. Hypertonic Solution
Concentration of the solute is higher outside the cell and lower inside the cell.
Water Exits the cell.
Think of the “E” in hypErtonic
Cell shrinks.

18. Hypertonic Solution

19. Assignment Draw and Label Figure 23, 24 and 25 on page 204-205.
Complete the Osmosis worksheet.