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MEMBRANE STRUCTURE BIO 100
OBJECTIVES Define details of membrane ultrastructure:
1. Explain the importance of plasma membranes
2. Discuss the molecular interactions between membrane components
3. Articulate how membrane components contribute to the properties and function of the plasma membrane
References
Alberts, Chapter 10- Membrane Structure
MEMBRANE FUNCTIONS
MEMBRANE PROPERTIES
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
THE LIPID BILAYER
LIPID COMPONENTS
phospholipids glycolipids
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
PACKING ARRANGEMENT
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
MEMBRANE FLUIDITY 10-8 cm2/sec
once a month
Internal factors that affect fluidity External factor that affects fluidity
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
LIPID RAFTS
• What type pf phospholipids do we expect to find in lipid rafts? • Why do proteins accumulate in lipid rafts? • Why are rafts rich in cholesterol? • In what way can lipid rafts help in cell function?
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
MEMBRANE ASYMMETRY Why asymmetric?
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al. New York: Garland Science; 2002.
MEMBRANE PROTEINS
• What type of amino acids can be found in the membrane section of 1/2/4?
• What type of molecules can be found in the external barrel of 3? internal barrel of 3?
• What type of bond is used in 5/6 for membrane docking?
• What type of bond is used in 7/8 for membrane docking?
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
MEMBRANE PROTEIN STRUCTURES
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al. New York: Garland Science; 2002.
GLYCOSYLATION
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
LATERAL DIFFUSION
aggregation
tethering
cell-cell interaction
How to restrict:
physical junctions
Molecular Biology of the Cell. 4th edition. Alberts B, Johnson A, Lewis J, et al.
New York: Garland Science; 2002.
MEMBRANE PROPERTIES What’s the molecular basis for the following properties?
1. Above is the lipid composition of various organisms. Answer the following questions based on the role of plasma membrane components. a. What is the predominant type (general, not specific) of lipid in all
organisms? Why? b. Why doesn’t E. coli need cholesterol and glycolipids? c. Why do mitochondria and ER have significantly low levels of
glycolipids?
2. Liposomes are currently used to deliver drugs or genetic material into cells. What is the principle behind this strategy? 3. Bacteria and fungi are normally exposed to varying temperatures. Knowing the effect of temperature on membrane fluidity, how come their plasma membrane remains undisturbed? 4. What will happen if lateral diffusion of proteins is unrestricted? 5. If a cell is exposed to glycosylation inhibitor, what will be affected: membrane structure or function? How? 6. A protein composed of hydrophilic amino acids was found to be membrane bound. How is this possible?