1. Cell Transport Notes

2. Cell Membrane Functions:
forms a boundary between inside and outside of the cell (provides protection and support)
Regulates passage of materials into and out of the cell.

3. Components of the Cell Membrane
Outside of cell
Carbohydrate chains
Proteins
Cell membrane
The cell membrane regulates what enters and leaves the cell.
Inside of cell (cytoplasm)
Protein channel
Lipid bilayer
Phospholipid
Cholesterol

4. Components of the Cell Membrane
Be able to identify:
Phospholipid
Cholesterol
Proteins
Transmembrane, integral, peripheral
Channel, pump, receptor, marker/signal
The cell membrane regulates what enters and leaves the cell.

5. Phospholipids Phospholipids are the major component of cell membranes
Hydrophilic
- likes water
- polar
Phosphate head
Fatty Acid Tails
Hydrophobic
- dislikes water
- non-polar

6. Lipid Bilayers (2 layers of phospholipids)
Heads
Phospholipids arrange themselves into two layers  aka phospholipid bilayer
The lipid bilayer gives the cell membranes a flexible structure that forms a barrier between the cell and its surroundings.
Layer #2

7. Molecules in the Membrane
Channel Proteins
Allow larger particles to pass through
Protein Pumps
Use energy to push molecules across the barrier
Receptor Proteins
Receive signals from the outside
Marker/signal Proteins
Give information about the cell to other cells
Have a carb attached to them

8. Cell Transport: Diffusion and Osmosis

9. Selective Permeability
The cell membrane is considered selectively permeable
What does this mean?

10. Selectively Permeable:
Allows some molecules to cross the membrane, while others cannot.

11. Why must the membrane be selective?
To maintain HOMEOSTASIS:
Organisms ability to maintain stability and adjust to environmental changes
To let in only necessary molecules such as:
water molecules
food particles
ions
To remove wastes such as:
Worn-out organelles
CO2
excess water
Undigested food

12. Passive Transport
Molecules pass through the cell membrane requiring no energy input from the cell

13. What is Diffusion? Diffusion:
Movement of particles from higher concentration to lower concentration.
When the concentration of the particles is the same throughout a system, the system has reached equilibrium.
Diffusion does not require the cell to use energy!

14. DIFFUSION

15. DIFFUSION

16. Diffusion Through Cell Boundaries
Diffusion is the process by which molecules of a substance move from areas of higher concentration to areas of lower concentration. Diffusion does not require the cell to use energy.

17. Factors that affect Diffusion
Heat:
The hotter the solution, the quicker it will diffuse
Size of Particles
Particles that are too large may not be able to diffuse because they can’t get through the semi permeable membrane
Small particles are also able to move faster so they diffuse faster
Concentration of Particles
The larger the difference, the faster the diffusion will happen

18. Perfume!
What do you think would happen?

19. Osmosis
Osmosis:
Osmosis is the diffusion of water through a selectively permeable membrane.
Goal: equilibrium
Think: making Gatorade

20. Selectively permeable membrane
Osmosis
How Osmosis Works
Dilute sugar solution (Water more concentrated)
Concentrated sugar solution (Water less concentrated)
Sugar molecules
Osmosis is the diffusion of water through a selectively permeable membrane. In the first beaker, water is more concentrated on the right side of the membrane. As a result, the water diffuses (as shown in the second beaker) to the area of lower concentration.
Movement of water
Selectively permeable membrane

21. Three Types of Solutions
A cell can be in three types of solutions:
Isotonic
Hypertonic
Hypotonic

22. Isotonic Solutions
Concentration of solution = concentration inside cell.
Cells in isotonic solution do not experience osmosis in one direction and retain their normal shape.
EX: Immunizations

23. Isotonic

24. Hypertonic Solutions
Concentration of solution > concentration inside cell
Cells in hypertonic solutions experience osmosis in which water moves through membrane to outside of cell.
Ex:
In plant cells, membrane and cytoplasm shrink away from cell wall and plant wilts (plasmolysis)
In animal cells, the pressure decreases and the cells shrivel.

25. Hypotonic Solutions
Concentration of solution < concentration inside cell
Cells in hypotonic solutions experience osmosis in which water moves through membrane into cell.
EX:
In animal cells, the pressure inside cell increases causing the cells to swell and sometimes burst!
In plant cells, the rigid cell wall prevents bursting, but the cells become more firm (turgor pressure)

27. Facilitated Diffusion
The passive transport of specific molecules across cell membranes through protein channels is known as facilitated diffusion.
Essentially, the molecules are being helped across the membrane!
If facilitated diffusion is considered Passive Transport, is there any energy used? NO

28. Facilitated Diffusion
Glucose molecules
During facilitated diffusion, molecules, such as glucose, that cannot diffuse across the cell membrane’s lipid bilayer on their own move through protein channels instead.
Protein channel

29. Active Transport Active transport requires energy!
Sometimes cells move materials in the opposite direction from which the materials would normally move—that is against a concentration difference. (from low to high concentrations)
This process is known as active transport.
Active transport requires energy!

30. Active Transport
Protein pumps use energy to move particles against a concentration gradient (from low concentration to high concentration)

31. Active Transport Molecule to be carried
Active transport of particles against a concentration difference requires transport proteins and energy.

32. Cellular Transport

33. What about the big boys?
ENDOCYTOSIS: cells surrounds and takes in material from environment by engulfing the material! YUMMY!
EXOCYTOSIS: cells expel materials from cell, such as waste or indigestible particles. GROSS!
Both endo and exocytosis are moving large masses of material and require energy (ACTIVE TRANSPORT!)

34. Endocytosis Phagocytosis: Psuedo arms take in food particles
Pinocytosis: NO psuedo arms are made as the cell takes in fluid.

35. Endocytosis and Exocytosis

36. 7-3 Unlike a cell wall, a cell membrane
is composed of a lipid bilayer.
provides rigid support for the surrounding cell.
allows most small molecules and ions to pass through easily.
is found only in plants, fungi, algae, and many prokaryotes.

37. 7-3 The concentration of a solution is defined as the
volume of solute in a given mass of solution.
mass of solute in a given volume of solution.
mass of solution in a given volume of solute.
volume of solution in a given mass of solute.

38. 7-3
If a substance is more highly concentrated outside the cell than inside the cell and the substance can move through the cell membrane, the substance will
move by diffusion from inside the cell to outside.
remain in high concentration outside the cell.
move by diffusion from outside to inside the cell.
cause water to enter the cell by osmosis.

39. 7-3
The movement of materials in a cell against a concentration difference is called
facilitated diffusion.
active transport.
osmosis.
diffusion.

40. 7-3
The process by which molecules diffuse across a membrane through protein channels is called
active transport.
endocytosis.
facilitated diffusion.
osmosis.

41. END OF SECTION