1. The Cell Membrane; Active & Passive Transport
Chapter 7.3
The Cell Membrane; Active & Passive Transport

2. Diffusion Molecules tend to “spread out”
Move from an area of high concentration to low concentration
Requires no energy

3. Diffusion
= The movement of molecules from an area of high concentration to an area of low concentration

4. Equilibrium

5. What’s this have to do with cells
What’s this have to do with cells? Think about it…cells are like a nation
Cells need things like a nation needs things…
Exports, imports
Has borders
Why may a cell need materials to leave or enter a cell?
How might this occur?

6. Cell Membrane Function: the GATEKEEPER1) 2) 3)

7. Cell Membrane Structure
Characteristics:

8. Cell Wall
Found in most prokaryotes and some eukaryotes (plants, fungi, algae)
Main function is support

9. Types of Cellular Transport
Animations of Active Transport & Passive Transport
high
low
Weeee!!!
Passive Transport
cell doesn’t use energy
Diffusion
Facilitated Diffusion
Osmosis
Active Transport
cell does use energy
Protein Pumps
Endocytosis
Exocytosis
high
low
This is gonna be hard work!!

10. Passive Transport (HighLow) cell uses no energy
molecules move randomly
Molecules spread out from an area of high concentration to an area of low concentration.
(HighLow)
Three types:

11. 3 Types of Passive Transport
Diffusion
Facilitated Diffusion – diffusion with the help of transport proteins
Osmosis – diffusion of water

12. Diffusion
In a cell:
- cytoplasm a solution of many different substances dissolved in water.
As you know:
-In any solution, solute particles tend to move from an area where they are more concentrated to an area where they are less concentrated.= Diffusion
Diffusion---- the driving force behind the movement of many substances across the cell membrane.

13. Passive Transport: 1. Diffusion
Simple Diffusion Animation
Passive Transport: 1. Diffusion
Diffusion: random movement of particles from an area of ______ concentration to an area of _______ concentration.
(__________________)
Diffusion continues until all molecules are evenly spaced (equilibrium is reached)-
Note: molecules will still move around but stay spread out.

14. 7-15 diagram pg 209
Discuss with a friend and DRAW: What would be different in 7-15 if the high concentration of solutes had been inside the cell to start with?

15. Facilitated diffusion (Channel Protein) Diffusion (Lipid Bilayer)
Passive Transport: 2. Facilitated Diffusion A B
2. Facilitated diffusion: diffusion of specific particles through transport proteins(protein channels/carriers) found in the membrane
Transport Proteins are specific – they “select” only certain molecules to cross the membrane
Transports larger or charged molecules
Facilitated diffusion (Channel Protein)
Diffusion (Lipid Bilayer)
Carrier Protein

16. Passive Transport: 2. Facilitated Diffusion
Glucose
molecules
Cellular Transport from a
High
High Concentration
Channel Proteins animations
Cell Membrane
to a Low Concentration
Protein
channel
Low
Transport Protein
Through a 
Go to Section:

17. Osmosis: A Type of Facilitated Diffusion
Inside of a cell’s lipid bilayer is hydrophobic—or “water-hating.”
water has a hard time getting through.
Water channel proteins, known as ______________________ allow water to pass right through them.
This movement of water is an extremely important biological =

18. Passive Transport: 3. Osmosis
Osmosis animation
3.Osmosis: diffusion of water through a selectively permeable membrane
Water moves from high to low concentrations
Water moves freely through pores.
Solute (green) too large to move across.

19. Rule for Osmosis:
Water will get sucked to wherever there is a higher concentration of salt.

20. Osmosis
= The diffusion of water across a selectively permeable membrane
ONLY THE WATER is moving.

21. How Osmosis Works
Barrier below is permeable to water but not to sugar.
-water molecules can pass through the solute, sugar, cannot.

22. How Osmosis Works
More sugar molecules on the
The concentration of water is __________________________ where more of the solution is made of sugar.

23. How Osmosis Works
There is a net movement of water into the compartment containing the concentrated sugar solution.
Water will tend to move across the barrier until equilibrium is reached. At that point, the concentrations of water and sugar will be the same on both sides.

24. How Osmosis Works
When the concentration is the same on both sides of the membrane, the two solutions will be ______________ which means “same strength.”

25. Osmotic Pressure
The net movement of water out of or into a cell produces a force known as osmotic pressure.
= the force created by the net movement of water through a cell membrane.

26. Isotonic Solution iso=same
Isotonic: The concentration of solutes in the solution is __________________ concentration of solutes inside the cell.
Result: Water moves equally in both directions and the cell remains same size!

27. Isotonic

28. Hypotonic Solution Hypo=less
Hypotonic: The solution has a _______ concentration of solutes and a __________ concentration of water than inside the cell. (_______solute; _______water)
Result: Water moves from the solution to inside the cell: Cell Swells and bursts open

29. Hypotonic

30. Hypertonic Solution hyper = more
Hypertonic: The solution has a ________ concentration of solutes and a ________ concentration of water than inside the cell. (_______ solute; ________ water)
shrinks
Result: Water moves from inside the cell into the solution: Cell shrinks

31. Hypertonic

32. B C A What type of solution are these cells in? Hypertonic Isotonic
Hypotonic

33. How Organisms Deal with Osmotic Pressure
Paramecium (protist) removing excess water video
Bacteria and plants have cell walls that prevent them from over-expanding. Pressure can damage the cell wall though.
A protist like paramecium has contractile vacuoles that collect water flowing in and pump it out to prevent them from over-expanding.
Salt water fish pump salt out of their specialized gills so they do not dehydrate.
Animal cells are bathed in blood. Kidneys keep the blood isotonic by remove excess salt and water.

34. Passive Transport Review
Requires no energy
Diffusion
Osmosis = Diffusion of water
Facilitated Diffusion: carrier proteins “help” molecules across the membrane like a tunnel

35. Active Transport (Low  High) cell uses energy
actively moves molecules to where they are needed
Movement from an area of low concentration to an area of high concentration
(Low  High)
Three Types:

36. Types of Active Transport
Sodium Potassium Pumps (Active Transport using proteins)
Protein Pumps –
Example: Sodium / Potassium Pumps are important in nerve responses.
Protein changes shape to move molecules: this requires energy!

37. Active Transport
Small molecules pumped into or out of cell by transport proteins on the cell membrane.
Transport goes against a concentration gradient
Requires cellular energy (ATP)

38. Types of Active Transport
2. _________________: taking bulky material into a cell
Uses energy
Cell membrane in-folds around food particle
“cell eating”
forms food vacuole & digests food
This is how white blood cells eat bacteria!

39. Types of Active Transport
3. __________________Forces material out of cell in bulk
membrane surrounding the material fuses with cell membrane
Cell changes shape – requires energy
EX: Hormones or wastes released from cell
Endocytosis & Exocytosis animations

41. Molecular Transport
A considerable portion of the energy used by cells in their daily activities is devoted to providing the energy to keep this form of active transport working.
The use of energy in these systems enables cells to concentrate substances in a particular location, even when the forces of diffusion might tend to move these substances in the opposite direction.

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