1. Cell Membrane

2. What cells have a cell membrane…
ALL cells have a cell membrane!
Prokaryotic and Eukaryotic

3. Cell Membrane’s Job…
Forms a boundary between a cell and the outside environment
Controls the passage of materials into and out of a cell

5. What is the cell membrane made of?
A double layer of phospholipids
Hydrophilic Heads-”water loving”-are exposed to water inside and outside the cell
Hydrophobic Tails-”water fearing”-cannot be exposed to water

6. Phospholipid

7. The cell membrane also has…
Molecules embedded within the phospholipid layers
Cholesterol molecules-provide strength for membrane
Proteins-help materials cross the membrane
Carbohydrates-attach to membrane proteins and serve as identification tags

8. Cell Membrane Structure
carbohydrate
chain
protein
cholesterol
protein
protein channel

9. Fluid Mosaic Model
Describes the arrangement of the molecules that make up the cell membrane
Cell membrane is flexible, not rigid.
The phospholipids in each layer can move from side to side and slide past each other.

10. Property of the Cell Membrane
Selective Permeability (semipermeable)
Cell membrane allows some, but not all, materials to cross into or out of the cell.
Enables cell to maintain homeostasis

11. Which side, outside or inside, has the highest/lowest concentration?
Concentration-number of particles present in a solution
Which side, outside or inside, has the highest/lowest concentration?

12. How do molecules move across the cell membrane?
Several different ways molecules will move.
Some ways require the cell to use energy and some do not.
How a molecule moves across the membrane depends on:
Size
Polarity
Concentration inside the cell vs. outside the cell

13. Examples of materials moving across the cell membrane…
Small nonpolar molecules move easily across the membrane
Small polar molecules are transported via proteins
Large molecules are moved in vesicles