Membrane Structure Chapter 11. Questions in this chapter you should be able to answer: Chapter 11- #s1 - 20. Membranes are described as a “2-dimensional liquid”. Why?. Jmol Membrane model. Laser tweezers. Membrane fluidity. How can we measure membrane fluidity?
Questions in this chapter you should be able to answer:
Chapter 11- #s1 - 20
a “2-dimensional liquid”. Why?
Jmol Membrane model
FRAP: ‘Fluorescence Recovery After Photobleaching’
GFP: Green fluorescent protein
Cell fusion also
See Figure 11-32
Properties of P-lipids: Chain length Saturation
Properties of membranes: Cholesterol content Cytoskeleton association
Other membrane lipids
Scamblase vs Flippase
P-lipids are synthesized on the ER membrane….
How do they get to other side of membrane?
How is asymmetry achieved?
From MBOC ed 5
How are membrane proteins connected to the membrane?
Membrane associated (peripheral)
Covalent vs Noncovalent
Why do transmembrane proteins occur as alpha helices and beta-pleated sheets??
Jmol Transmembrane proteins
-- detergents ‘mimic’ P-lipid structure around proteins
Why is red part hydrophilic and blue part hydrophobic?
the structure of bacteriorhodopsin?
-- Cell cytoskeleton
-- also influences fluidity
-- extracellular matrix
Consider challenge of intestinal epithelium…
Fig 12-18 p 399
You have isolated two mutants of a normally pear-shaped microorganism that have lost their distinctive shape and are now round. One of the mutants has a defect in a protein you call A and the other has a defect in a protein you call B. You grind up each type of mutant cell and normal cells separately and separate the plasma membranes from the cytoplasm by centrifugation. You then wash the membrane fraction with a low concentration of urea ( which disrupts their ability to interact with other proteins) and centrifuge the mixture. The membranes and their constituent proteins form a pellet while the proteins liberated by the urea wash remain in the supernatant. When you check each of the fractions for the presence of A or B, you obtain the results given below.
Answer the following statements about your results?
(a) Which is an integral and which is a peripheral membrane-associated protein. The results for which cell-type shows this?
(b) How does the mutation to protein-A alter its properties.
(c) How does the mutation to protein-A alter its properties.
(d) Which result(s) most indicate an interaction between A and B. Explain.