1. Membrane Structure and Function
6.1 Plasma membrane structure

2. What is the plasma membrane (PM) like?
Fluid mosaic model
Consistency of salad dressing
Highly fluid

3. What is the PM made of? Three components Phospholipids Cholesterol
Proteins
Peripheral
structural
Transmembrane
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4. What do the transmembrane proteins do?
Channels
Carriers
Cell recognition
Receptors
Enzymes

5. What else is found in the PM?
Carbohydrate chains
Attached to proteins
Glycoproteins
Glycocalyx
Also lipid chains
lipoproteins

6. Membrane Structure and Function
6.2 Permeability

7. What is allowed to cross the PM?
PM is selectively permeable
Molecules that easily cross
O2, N2, CO2, H2O, alcohol
Move down concentration gradient

8. What is diffusion? Movement down concentration gradient
Solution = solute + solvent

9. What is osmosis?
Water down concentration gradient

10. What is osmotic pressure?
Pressure due to osmosis
Isotonic solutions
Water still moves!
Hypertonic solutions
plasmolysis
Hypotonic solutions
Turgor pressure

11. What would happen to each cell?

12. Membrane Structure and Function
6.3 Carrier proteins

13. What about items that cannot cross the PM freely?
Three possibilities:
1. Facilitated transport
Down concentration gradient
NO ATP

14. What about items that cannot cross the PM freely—2?
2. Active transport
UP the concentration gradient
Uses ATP
E.g. Na+/K+ pump
2 K+ ____, 3 Na+ ___

15. What about items that cannot cross the PM freely—3?
3. Vesicle formation
Endocytosis
Receptor-mediated
Exocytosis
Pinocytosis
Phagocytosis
Uses ATP

16. Membrane Structure and Function
6.4 Cell junctions

17. What cell junctions are found in animal cells?
Anchoring junctions
Adhesion junctions
Desmosomes
Tight junctions
Gap junctions

18. What is the extracellular matrix (ECM)?
Polysaccharides and proteins
Collagen = strength
Elastin = resilence
Adhesion proteins
Fibronectins
Laminins
We’ll talk more about ECM in histology

19. What is in plant cell walls?
Cellulose
Compare to
Fungi
Bacteria
Plasmadesmata
Connect plant cells