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A graduate student is studying cell membranes in the rare silver Arctic fox

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1. A graduate student is studying cell membranes in the rare silver Arctic fox.  Specifically he is comparing cell membranes in the fox’s feet and in the fox’s shoulder.  Surprisingly he finds the composition of these membranes to be different.  Based on your knowledge of cell membranes and melting temperatures, predict which type of cell membrane (those in feet or shoulder) will have a lower melting temperature and why the fox has adapted this survival strategy.   Include in your explanation a discussion of how fatty acid composition impacts melting temperature and how this is related to the fox example.  [Note:  the fox spends a lot of time walking around in the snow.]

2. A graduate student is comparing the activity level of the mutated form of the armadillo enzyme to the activity level of the normal (wild type) armadillo enzyme.  Initially both enzymes display the same activity level.  However after six hours the activity of the mutated form decreases while the activity of the normal protein remains constant.  Structural studies of the mutated enzyme indicate binding of the substrate to the enzyme, catalysis to convert substrate to product and release of product are all normal.  An additional experiment finds the concentration of messenger RNA coding for normal armadillo protein is equal to the concentration of messenger RNA coding for the mutated armadillo protein and these values remain equal initially and after six hours.   One experiment found labeled ubiquitin bound to the mutated enzyme but NOT the wild type enzyme.  Explain these results.  Design an experiment to test your hypothesis.