1. Cell Membrane

2. Cell Membrane Every cell has a cell membrane.
Protects the cell and helps move substances and messages in and out of the cell.
By regulating transport the membrane helps the cell maintain constancy and order.

3. Homeostatsis
Homeostasis is the maintenance of stable internal conditions in a changing environment.
Individual cells along with organisms, must maintain homeostasis in order to live.
A cell maintains homeostasis by controlling the movement of substances across the cell membrane.

4. Structure Phospholipid Bilayer Membrane Proteins Carbohydrates
Hydrophilic (Water-Loving) Heads
Hydrophobic (Water-Fearing) Tails
Membrane Proteins
For transport through membrane
Carbohydrates
Attached carbohydrates can hold cells together
Viruses and chemical messages can attach to carbs too.

5. Phospholipid
Hydrophilic head
Protein
Hydrophobic tail

6. Movement of Molecules Passive Transport Active Transport
All movement of molecules across a membrane is one of two types of transport.
Passive Transport
No energy required
Molecules move from high to low concentration.
Active Transport
Energy required
Molecules almost always move from low to high concentration

7. Which is more concentrated?B A

8. Passive Transport Diffusion
Is the natural tendency of molecules to move from high to low concentration.
Some molecules can pass through the openings in the cell membrane.
Others cannot. They require a protein helper. This process is called facilitated diffusion.
Osmosis is one example of facilitated diffusion.
Osmosis is the diffusion of water.

9. Osmosis
Water moves via osmosis from hypotonic to hypertonic solutions.
Solute: a dissolvable substance (ex. Kool Aid)
Solvent: liquid used to dissolve a substance (ex. water).
Hypertonic
A solution that has more solute than another.
Isotonic
A solution that has the same amount of solute as another.
Hypotonic
A solution that has less solute than another.

10. Diffusion of dye in water

12. OSMOSIS IN RED BLOOD CELLS

14. Plant Cell OSMOSIS

15. Practice What is the solute? What is the solvent?
If water can move through the bag, but salt cannot, which way will the water move?
1% Saltwater
2% Saltwater

16. Practice What is the solute? What is the solvent?
If water can move through the bag, but salt cannot, which way will the water move?
4% Saltwater
2% Saltwater

17. Practice What is the solute? What is the solvent?
If water can move through the bag, but sugar cannot, which way will the water move?
1.5% Sugar water

19. Active Transport Require energy Cell Membrane Pumps Two types
Proteins in membrane that push molecules from low concentration to high concentration.
Example is the Sodium/Potassium Pump
Moves sodium ions out and potassium ions in
Two types
Endocytosis
Exocytosis

20. Active Transport Endocytosis Exocytosis
Movement of molecules into the cell through a vesicle or vacuole, created by the cell membrane.
Phagocytosis – movement of large molecules such as food; “cell eating”.
Pinocytosis – movement of small molecules such as water; “cell drinking”.
Exocytosis
Movement of molecules out of the cell through a vesicle that fuses with the cell membrane.

21. Vesicle Fusing with Membrane