1. CELL MEMBRANE FUNCTION
PASSIVE DIFFUSION, OSMOSIS, FACILITATED DIFFUSION AND ACTIVE TRANSPORT

2. The Cell Membrane Question of the Day:
How Is the Structure of a Membrane Related to Its Function?

3. (b) Enzymatic activity (c) Signal transduction
MEMBRANE PROTEINS
Signaling molecule
Enzymes
Receptor
ATP
Signal transduction
(a) Transport
(b) Enzymatic activity
(c) Signal transduction
Glyco-
protein
(d) Cell-cell recognition
(e) Intercellular joining
(f) Attachment to
the cytoskeleton
and extracellular
matrix (ECM)

4. EXTRACELLULAR
SIDE
N-terminus
C-terminus
CYTOPLASMIC
SIDE
 Helix

5. Importance 1. Acquire molecules & Ions 2
Importance 1. Acquire molecules & Ions 2.Transport into and out of cell through membrane 3.Transport WITHIN the cell ER 1
Transmembrane
glycoproteins
Secretory
protein
Glycolipid
Golgi
apparatus 2
Vesicle 3
Plasma membrane:
Cytoplasmic face 4
Extracellular face
Transmembrane
glycoprotein
Secreted
protein
Membrane glycolipid

6. Cell Membrane Function
Problems and Solutions 1. Relative concentrations Passive Transport Active Transport 2. Lipid bilayers are impermeable to most essential molecules and ions permeable to: small non polar molecules

7. Cell membrane function, con’t
b. impermeable to: -

8. SIMPLE DIFFUSION REQUIRES A CONCENTRATION GRADIENT
FACILITATED DIFFUSION REQUIRES A CONCENTRATION GRADIENT AND A PROTEIN TRANSPORTER

9. Use you membrane models to show diffusion
Molecules of dye
Membrane (cross section)
WATER
Net diffusion
Net diffusion
Equilibrium
(a) Diffusion of one solute

10. Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
(b) Diffusion of two solutes

11. Use your models to show facilitated diffusion
Use your models to show facilitated diffusion. What molecules would you want to transport this way?
EXTRACELLULAR FLUID
Channel protein
Solute
CYTOPLASM
(a) A channel protein
Solute
Carrier protein
(b) A carrier protein

12. REQUIRES A PROTEIN TRANSPORTER AND ATP ENERGY
ACTIVE TRANSPORT
REQUIRES A PROTEIN TRANSPORTER AND ATP ENERGY

13. Active transport:
ATP

14. 1 2 3 6 5 4 EXTRACELLULAR FLUID [Na+] high Na+ [K+] low Na+ Na+ Na+
[Na+] low
ATP
Na+ P P
CYTOPLASM
[K+] high
ADP 1 2 3 K+ K+ K+ K+ K+ P K+ P 6 5 4

15. –
EXTRACELLULAR
FLUID +
ATP – + H+ H+
Proton pump H+ – + H+ H+ H+ – +
CYTOPLASM H+ – +

16. – + H+ ATP H+ – + H+ H+ – + H+ H+ – + H+ H+ – + – + Diffusion of H+
Proton pump H+ H+ – + H+ H+ – + H+
Diffusion
of H+
Sucrose-H+
cotransporter H+ –
Sucrose + – +
Sucrose

17. Facilitated diffusion
REVIEW
Passive transport
Active transport
ATP
Diffusion
Facilitated diffusion

18. Osmosis
Passive Diffusion of Water Vocabulary: Hypertonic, hypotonic, isotonic, osmotic pressure, tonicity, turgid, flaccid, lyse.

19. cell cell Hypotonic solution Isotonic solution Hypertonic solution H2O
(a) Animal
cell
Lysed
Normal
Shriveled
H2O
H2O
H2O
H2O
(b) Plant
cell
Turgid (normal)
Flaccid
Plasmolyzed

20. What would happen to the animal cells in each beaker?
100% Distilled Water
70% Water 30% Dissolved Substances
80% Water 20% Dissolved Substances
Ask the students to predict what would happen to the cells in the beaker. You may want to explain solutions first. Dissolved substances would be sugars, salts, ions, etc.

21. Which way did the water move?
100% Distilled Water
0% dissolved substances
80% H2O
20% “stuff”
Have the students predict – and then show the answer. You have to click to get the beaker and the question to show.
Why did the cell get so big?
Hypotonic solution

22. Which way did the water move?
80% Water 20% Dissolved Substances
80% H2O
20% “stuff”
Predict and show answer.
Why did the cell stay the same size?
Isotonic solution

23. Which way did the water move?
70% Water 30% Dissolved Substances
80% H2O
20% “stuff”
Predict and show answer.
Why did the cell get so small?
Hypertonic solution

24. Let’s look at what happens to your blood cells in the three different solutions:
Isotonic (equal)
Hypertonic (high)
Hypotonic (low)

25. Environment:
0.01 M sucrose
0.01 M glucose
0.01 M fructose
“Cell”
0.03 M sucrose
0.02 M glucose

26. Lower
concentration
of solute (sugar)
Higher concentration
of sugar
Same concentration
of sugar
H2O
Selectively
permeable
membrane
Osmosis

27. Additional transport Mechanisms
Bulk Transport
Endocytosis
Phagocytosis
Pinocytosis
Receptor-mediated
endocytosis

28.
PHAGOCYTOSIS
EXTRACELLULAR
FLUID
CYTOPLASM
1 µm
Pseudopodium
Pseudopodium
of amoeba
“Food” or
other particle
Bacterium
Food
vacuole
Food vacuole
An amoeba engulfing a bacterium
via phagocytosis (TEM)

29. Phagocytosis Your white bloods cells also do this.
Amoeba
Make sure to point out that the diagram is an amoeba, not a human cell. As the “food particle” moves in the cell, it fuses with lysosomes to be digested.
Your white bloods cells also do this.
This is the ingestion of large particles.

30. PINOCYTOSIS Plasma membrane Vesicle 0.5 µm Pinocytosis vesicles
forming (arrows) in
a cell lining a small
blood vessel (TEM)
Vesicle

31. Pinocytosis
For animation, point out to the students that the cell doesn’t “spit” the contents out, like it does in the picture. The particles move into the cell and become part of a vacuole.
Tiny pockets form along cell membrane, and pinch off into vacuoles inside the cell. Sometimes called “Cell Drinking”

32. Coat protein Receptor Coated vesicle Coated pit Ligand A coated pit
RECEPTOR-MEDIATED ENDOCYTOSIS
Coat protein
Receptor
Coated
vesicle
Coated
pit
Ligand
A coated pit
and a coated
vesicle formed
during
receptor-
mediated
endocytosis
(TEMs)
Coat
protein
Plasma
membrane
0.25 µm

33. Exocytosis This is how the cell gets rid of waste.
The blue particle should have “waste” particles in it, but does not. Make sure this is pointed out to the students. The waste fuses to the cell membrane and is then released into the environment.
This is how the cell gets rid of waste.