1. Cell Membranes and Transport

2. 
Homeostasis
Homeostasis is the balance cells must maintain with their surrounding environment.
Cells maintain homeostasis by controlling what enters and exits the cell.

3. Hydrophilic Hydrophobic
The Cell Membrane
Made of a bilayer of phospholipids
Phospholipids have a hydrophobic tail (water fearing) and hydrophilic head (water loving).
Proteins are embedded in the membrane to help move materials in-and-out of the cell.
Hydrophilic
Hydrophobic

4. The membrane is called a fluid-mosaic – why?

5. Draw Me! The Cell Membrane
Figure 7-12 The Structure of the Cell Membrane
The Cell Membrane
Section 7-3
Outside
of cell
Inside
(cytoplasm)
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains
Draw Me!

6. 
The Cell Membrane
Cell membranes are SELECTIVELY PERMEABLE – what does this mean?
The cell membrane has some control over what can cross it, so that only certain molecules either enter or leave the cell. 
Ex. The strainer lets water pass through, yet keeps the pasta in. It is selectively permeable.

7. 
Passive Transport
Movement of molecules across the cell membrane that DOES NOT USE ENERGY.
Materials move from an area of HIGH CONCENTRATION to an area of LOW CONCENTRATION.

8. 
Diffusion
Diffusion – Movement of molecules through the cell membrane
A type of PASSIVE TRANSPORT because it DOES NOT USE ENERGY.

9. Diffusion Checkpoint
What direction will the molecules move?

10. Diffusion Checkpoint Pt. 2
Diffusion Checkpoint Pt. 2
When is equilibrium reached?
EQUILIBRIUM is reached when concentrations are equal on both sides of the cell membrane.

11. Osmosis  Osmosis – diffusion of WATER molecules through the cell
membrane (passive transport)
Water always diffuses from an area of LOW SOLUTE CONCENTRATION to an area of HIGH SOLUTE CONCENTRATION.
OR  High Water Concentration to Low Water Concentration
Solute is…..??

12. Osmosis

13. Osmosis – Driven by Solute Concentration
Osmosis – Driven by Solute Concentration
Hypotonic solution – solute concentration is lower on the outside of the cell than inside the cell.
Water moves INTO the cell
Hypo= low, below normal

14. Osmosis – Driven by Solute Concentration
Osmosis – Driven by Solute Concentration
Hypertonic solution – solute concentration is higher on the outside of the cell than inside the cell.
Water moves out of the cell
Hyper= excessive

15. Osmosis – Driven by Solute Concentration
Osmosis – Driven by Solute Concentration
Isotonic solution – solute concentration is equal on both sides of the cell membrane.
Water diffuses in-and-out equally
Iso= equal or the same

16. Osmosis and Plant Cells
Osmosis and Plant Cells
Plant cells require a hypotonic environment so water moves into the cell and the cell swells
Swelling of the cell builds up turgor pressure

17. Osmosis and Plant Cells
Osmosis and Plant Cells
Plant cells in hypertonic environments lose water and the cell shrivels up.
Shriveling of the cell is called plasmolysis.

18. Class Demo! Osmosis Checkpoint
What would happen to animal cells in hypotonic and hypertonic environments?
Class Demo!

19. Osmosis
For example, marine fish:

20. Complete Osmosis Pre-Lab Work

21. Recall – Osmosis – WHAT WILL HAPPEN TO THE CELL???

22. Facilitated Diffusion
Facilitated Diffusion
Facilitated diffusion - moves molecules in-and-out of the cell using a carrier protein (passive transport)
Why would molecules need help from a carrier protein?
Too big
Charged
Can not dissolve in the phospholipid bilayer.

23. 
Active Transport
Active transport - movement of molecules across the cell membrane that requires energy.
Can move materials from an area of LOW CONCENTRATION to an area of HIGH CONCENTRATION. (Opposite of diffusion)

24. Active Transport Why does your body need to use active transport?
Na+/K+ pumps for neuron function
SWEET Video
Animation of Sodium/Potassium Pumps

25. 
Endocytosis
Large molecules can be engulfed by cells in a process called ENDOCYTOSIS. (Active transport)
Pinocytosis - process of engulfing a liquid. (“Cell drinking,”)
Phagocytosis - process of engulfing a solid. (“Cell eating,”)

26. Endocytosis

27. Exocytosis – release material from the cell
Exocytosis – release material from the cell