1. CELL MEMBRANE STRUCTURE & FUNCTIONS
PASSIVE DIFFUSION, OSMOSIS, FACILITATED DIFFUSION AND ACTIVE TRANSPORT

2. WATER
Hydrophilic
head
Hydrophobic
tail
WATER

3. Phospholipid
bilayer
Hydrophobic regions
of protein
Hydrophilic
regions of protein

4. TECHNIQUE
RESULTS
Extracellular
layer
Proteins
Inside of extracellular layer
Knife
Plasma membrane
Cytoplasmic layer
Inside of cytoplasmic layer

5. Lateral movement
(~107 times per second)
Flip-flop
(~ once per month)
(a) Movement of phospholipids
Fluid
Viscous
Unsaturated hydrocarbon
tails with kinks
Saturated hydro-
carbon tails
(b) Membrane fluidity
Cholesterol
(c) Cholesterol within the animal cell membrane

6. Cell Membrane Structures
Recognition Factors
Antenna that capture required solutes/hormnones
Amphipathic nature of the phospholipids and its consequences
Integral Proteins

7. Fibers of extracellular matrix (ECM) Glyco- Carbohydrate protein
Glycolipid
EXTRACELLULAR
SIDE OF
MEMBRANE
Cholesterol
Microfilaments
of cytoskeleton
Peripheral
proteins
Integral
protein
CYTOPLASMIC SIDE
OF MEMBRANE

8. (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)

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

10. 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

11. Cell Membrane Function
Problems and Solutions 1. Relative concentrations a. Passive Transport b. Active Transport 2. Lipid bilayers are impermeable to most essential molecules and ions a. permeable to:

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

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

14. Molecules of dye
Membrane (cross section)
WATER
Net diffusion
Net diffusion
Equilibrium
(a) Diffusion of one solute

15. Relate to Lab: Glucose, Starch. NaCl, Proitein
Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
(b) Diffusion of two solutes

16. Channel protein Solute (a) A channel protein Solute Carrier protein
EXTRACELLULAR FLUID
Channel protein
Solute
CYTOPLASM
(a) A channel protein
Solute
Carrier protein
(b) A carrier protein

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

18. Active transport:
ATP

19. 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

20. –
EXTRACELLULAR
FLUID +
ATP – + H+ H+
Proton pump H+ – + H+ H+ H+ – +
CYTOPLASM H+ – +

21. – + 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

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

23. Osmosis Passive Diffusion of Water Dissociation of ions in solution
Aquaporins
Osmotic concentration
Free Energy
Water Potential

24. Tonicity of cell IN COMPARISON TO the environment:
The cell is ________in comparison to the environment. Hence, water will move from _____________________ to ____________.
The results:
Cell Interior:
Less than 1% solute
ENVIRONMENT 99% water

25. 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

26. Cell with less than 1 % solute
Cell with less than 1 % SOLUTE (freshwater cell with more than 99% water)
Cell with less than 1 % solute
Environment with greater than 10% SOLUTE (less than 90 % water)
Cell
Environment
Osmotic or Solute Potential -
Free Energy
Osmotic Potential
Osmotic Pressure
Water Potential Ψ

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

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

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

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

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

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