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1. Plasma Membrane
Structure and
Function
Chapter 4

2. Outline
•Phospholipid Bilayer
•Fluid Mosaic Model
•Membrane Proteins
•Diffusion
•Facilitated Diffusion
•Osmosis
•Bulk Transport
•Active Transport

3. Membrane Functions
•Protection
•Communication
•Selectively allow substances in
•Respond to environment
•Recognition

4. Plasma Membrane
•Boundary that separates the living cell from
it’s non-living surroundings.
•Phospholipid bilayer
•Amphipathic - having both:
hydrophilic heads
hydrophobic tails
•~8 nm thick
•Is a dynamic structure
PhospholipidPhospholipid

5. Fluid-Mosaic Model

6. Proteins—For Function
•Transport
•Receptors
•Enzymes
•Signal Transducers
•Support

7. PROTEINS CAN
MOVE IN THE
MEMBRANE, T
OO!
Plasma Membrane Proteins

8. Channel protein

9. Carrier protein

10. Cell recognition protein

11. Receptor protein

12. Enzymatic protein
Example of
Enzymatic
activity
associated
with a
membrane
:
G-protein c
ascade
G-PROTEIN A
NIMATION 2

G-protein anim
ation 3

13. Permeability of the Cell Membrane-
Differentially PermeableDifferentially Permeable

14. Permeability of the Cell Membrane

15. •Diffusion
– the passive movement of molecules from
a higher to a lower concentration until
equilibrium is reached.
–How can we explain diffusion?
–Gases move through plasma membranes
by diffusion.
•Osmosis– A special case of diffusion
DIFFUSION

16. Process of diffusion

19. Gas exchange in lungs by diffusion

20. Osmosis
The diffusion of water across a
differentially permeable
membrane due to
concentration differences

21. Question:
What’s in a Solution?
Answer:
•solute+solventsolution
•NaCl +H
2
0 saltwater

22. TONICITY
•Refers to the concentration of
SOLUTES
•Is a RELATIVE term, comparing two
different solutions
•Hypertonic
•Hypotonic
•Isotonic

23. Hypertonic
•A solution with a greater solute
concentration compared to another solution.
3% NaCl
97% H
2O
Red Blood Cell
5% NaCl
95% H
2
O
solutionsolution
Which
way
will
the
water
move
?

24. Hypotonic
•A solution with a lower solute concentration
compared to another solution.
3% Na
97% H
2O
Red Blood Cell
1% Na
99% H
2
O
solutionsolution
Which
way
will
the
water
move
?

25. Isotonic
•A solution with an equal solute concentration
compared to another solution.
3% Na
97% H
2
O
Red Blood Cell
3% Na
97% H
2
O
solutionsolution
Which
way
will
the
water
move
?

26. ISOTONIC SOLUTION

27. HYPOTONIC SOLUTION

28. HYPERTONIC SOLUTION

29. •Function—Transport. Are specific,
combine with only a certain type of
molecule.
•Types
–Facilitated transport--passive
–Active transport—requires energy
Carrier Proteins (Trans-membrane Proteins)

30. Facilitated Transport

31. Active Transport

32. The sodium-potassium pump

33. •Exocytosis---Cellular secretion
•Endocytosis—
–Phagocytosis— “Cell eating”
–Pinocytosis– “Cell drinking”
–Receptor-mediated endocytosis-
specific particles, recognition.
Exocytosis and
Endocytosis

34. Exocytosis

35. Phagocytosis
Phagocytosis 1
Phagocytosis 2

36. Pinocytosis

37. Receptor-mediated
Endocytosis