1. Cell Boundaries

2. Cell membrane
thin, flexible barriers that surrounds all cells and separate some areas within cells

3. Cell membrane organelles are surrounded by cell membranes
organelles are special structures in cells that perform a specific function (ex: mitochondria, chloroplasts, nucleus)
organelles = little organs

4. Cell membrane
composed of phospholipid bilayers

5. Plasma membrane cell membrane on the outside of the cell
regulates (controls) what enters and leaves the cell
provides protection and support
sometimes just called THE cell membrane

6. Beginning Watching at 9:42
Phospholipid
have two distinct ends
CrashCourse Biology
Episode #3
You Are What You Eat
Beginning Watching at 9:42
Stop Watching at 10:27

7. Phospholipids Phosphate end Water Soluble Hydrophilic “Water Loving”
Lipid end
Water Insoluble
Hydrophobic
“Water Hating”

8. When placed in water, how will these molecules arrange themselves?
into a hollow sphere
water hating (insoluble) ends will "stick together"

9. When placed in water, how will these molecules arrange themselves?
will form a bilayer to keep lipid ends away from water outside of the cell and away from the water inside the cell
Outside the cell
Inside the cell

10. Phospholipid bilayer as a Barrier
The lipid portion in the center is very oil like. This oil like layer repels water, and water-soluble molecules.
Most molecules inside or outside of the cell are water-soluble and cannot easily pass through this oil like layer.
This layer thus forms a barrier to most molecules trying to pass in or out of a cell.

11. Membrane Proteins
protein molecules embedded within the phospholipid bilayer
They may form channels. If small enough, water-soluble molecules can cross the barrier through the protein channel.
Other protein molecules are located on the inside or outside surface of the membrane and "transport" or move particular molecules across the membrane using energy.

12. Membrane Proteins

13. Cholesterol
lipid embedded in the phospholipids of the cell membrane that prevents the membrane from becoming too solid or too fluid
helps the cell membrane tolerate temperature changes

14. Membrane Carbohydrates
serve as identifying markers on the outside of cells
helps identify the cell and its function to other cells

15. Membrane Carbohydrates
form many of the antigens on the outside surfaces of cells
sometimes combine with proteins to form glycoproteins

16. Cell Wall found in plants, fungi, some protists, and prokaryotes
provides a large amount of support and protection for the cell
made of the carbohydrate cellulose in plants
NOT a barrier to the movement of molecules

17. Summary
Identify one similarity and one difference between a plasma membrane and a cell wall.