1. MOVEMENTS THROUGH THE CELL MEMBRANE

2. Importance
All organisms need to maintain a balance in their internal environment.
This balance is called?
Homeostasis
The cell membrane is vital to cell homeostasis because it controls the movement of molecules into and out of the cell. This is called?
Selective permeability

3. Passive movement of substances through the cell membrane (no cellular energy required)
Diffusion: The process by which molecules or ions scatter or spread spontaneously from regions of high concentration to low concentration.
What happens to the piece of candy when you place it in water?
O seconds
20 seconds
40 seconds
6O seconds

4. What happens to the molecules (red dots) over time
What happens to the molecules (red dots) over time? The final equal distribution of molecules is called a “state of equilibrium”.

5. 2.Facilitated diffusion: When molecules are too large to pass through the pores of the cell membrane, carrier molecules carry the large molecules from regions of higher to areas of lower concentration.
3. Filtration: Movement of molecules across a membrane as a result of pressure
Watch this animation.
What human body example of filtration was provided?
Read page 62 of your text. What is a human body example of facilitated diffusion?

6. Why is it called “facilitated diffusion”?

7. How is filtration different than diffusion?

8. 4. Osmosis: A special case of diffusion in which water molecules diffuse from regions of higher concentration to area of lower concentration.
Watch the animation.
How does water move across a cell membrane?
Why do you think the movement of water across a cell membrane is important?

9. What do you think will happen to red blood cells when the are placed in a hypertonic solution? Watch the video.

10. What do you think will happen to red blood cells when the are placed in a hypotonic solution? Watch the video.

11. Active Mechanisms (Use cellular energy)
1. Active transport -process that moves particles through membranes from regions of lower concentration to regions of higher concentration. animation and quiz amazing students
Uses specific carrier molecules (pumps)
Uses 40% of the cell’s energy
Particles transported include sugars, amino acids, sodium, potassium, calcium and hydrogen ions

12. 2. Endocytosis- large particles are brought into a cell through vesicles
a. pinocytosis- cell
takes in liquids
b. phagocytosis- cell
takes in solids
3. receptor mediated
-specific molecules
move into cell
3. Exocytosis- a substance stored in a vesicle is released from the cell
Animation

13. What would a human cell take in by endocytosis?
What would a human cell eliminate via exocytosis?

14. Summary
Passive transport- the cell does not expend energy 1. diffusion -movement of molecules -no force 2. osmosis -diffusion of water molecules 3. filtration -membrane (filter) present -force

15. Summary
Active transport- the cell uses energy to move molecules 1. active transport -pumps are used 2. endocytosis -cell engulfs solids or liquids 3. exocytosis -cell releases substances