1. 7.3 Movement Through the Membrane

2. Obvious Questions: What do we breath in? Why? What do we breath out?
Why do we eat?
Where does our waste come from?

3. Introduction to Movement Through the Membrane
Selectively Permeable – Some things can pass through and others cannot
oxygen
Carbon dioxide
water
proteins
food

4. Cell Membrane
Regulates what enters and leaves the cell, and also provides protection and support

5. The Structure of the Cell Membrane
Section 7-3
Core is lipid bi-layer
Proteins form channels and pumps that help to
move material into and out of cell
Carbohydrates act as identification cards
(immune system).
Outside
of cell
Cell
membrane
Proteins
Protein
channel
Lipid bilayer
Carbohydrate
chains
Inside
of cell
(cytoplasm) :

6. Diffusion Movement of molecules from a high to low concentration sugar
High concentration of sugar
20 gram/Liter
Cell membrane
Low concentration of sugar
10 grams/Liter

7. Osmosis – Diffusion of water
Osmosis – Diffusion of water across a selectively permeable membrane.
Example (oatmeal, raisin)

8. Osmosis Cell membrane Section 7-3 Water molecules Higher Concentration
of Water
Cell
membrane
Lower Concentration
of Water
Sugar molecules

9. Solutions
add the salt
Isotonic – the solution outside the cell is equal to the solution of the cytoplasm. Iso means the same.
Water will move equally in both directions.
No net movement across cell membrane.
90%
90%
Isotonic solution

10. Solutions
Hypertonic – the solution outside the bag is “hyper” meaning it is above strength. Hyper means high so the solution is high in solute, low in water.
Water will move in both directions but more will move to an area of low concentration. This will cause the cell to lose water.
H2O
90%
70%
Hypertonic solution
More solute = less water

11. Solutions
Hypotonic – the solution outside the bag is “hypo” meaning below strength. Hypo means below so the solution is low in solute and high in water.
Water will move in both directions but more will move inside the cell.
H2O
70%
90%
Hypotonic solution

12. Same as inside
the cell.
High in solute
Low in water.
Low in solute
High in water
Cell will swell Cell will not change Cell will shrink

13. Diffusion and Osmosis through the cell membrane (small molecules such as H2O, O2, CO2)

15. Facilitated Diffusion
Section 7-3
Glucose
molecules
High
Concentration
Cell
Membrane
Low
Concentration
Protein
channel
Facilitated Diffusion – diffusion through a protein channel
Larger molecules like sugars – because to large to pass through.
No energy required from cell.
Go to Section:

16. Active Transport
Section 7-3
Molecule to
be carried
Molecule
being carried
Energy
Low
Concentration
Cell
Membrane
Active transport is an energy requiring process moving molecules from a low concentration to a high concentration.
High
Concentration
Low
Concentration
Cell
Membrane
High
Concentration
Go to Section:

17. Active Transport Methods
Endocytosis (phagocytosis) – Taking things “into” the cell by infoldings or pockets of the cell membrane. Food, whole cells. #23 Forms a vacuole inside cell.
Exocytosis – Exiting out of cell by the same process. Pocket forms with cell membrane to expel wastes.
endocytosis (phagocytosis)