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?