Jan%2012%20questions

Jan%2012%20questions - Question: Which of these...

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Question: Five students in your class always sit together in the front row. This could be because: (a) they really like each other, or (2) nobody else in the class wants to sit next to them. Which answer holds for the assembly of lipids into a bilayer in water? Answer (2): Water excludes lipids. How might membranes be different if (1) was correct? Answer: If lipids attracted each other and formed bonds, membranes might be less fluid or even rigid. Question: Which of the following organisms will have the highest percentage of unsaturated fatty acid chains in their membranes? A. Antarctic fish B. Desert iguana C. Human being D. Polar bear E. Thermophilic bacterium Answer: A. Antarctic fish- cold-blooded. UFAs counteract the effects of cold: cold makes membranes less fluid, UFAs make membranes more fluid.
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Unformatted text preview: Question: Which of these arrangements of proteins have been found in biological membranes? Answer: A, B, D, E, F, I C: carbohydrate on cytoplasmic side never found G: protein completely buried never found, theoretically unlikely H: tip only in membrane never found, unlikely Bonus Question (not used in class): Question: Why are membrane-spanning protein segments almost always alpha-helices or beta-barrels, but never disordered chains? Answer: In both alpha- helix and beta-barrel, the polar H-bonding groups in the peptide bond make internal hydrogen bonds with other peptide bonds. In a disordered chain the peptide polar groups are not bonded to each other or to lipid. As a result, a disordered peptide chain in a membrane is energetically very unfavorable....
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Jan%2012%20questions - Question: Which of these...

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