7.012_Section_1-solution_key_-2010 - Questions: Solution...

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1 Solution key - 7.012 Recitation 1 - 2010 Questions: 1. Oil is fluid at room temperature but butter is solid. Which types of fat do you think predominates in oil and butter (saturated/unsaturated)? Butter is comprised of saturated fatty acids that only have single bonds, which allow close packing. In comparison, oil is comprised of unsaturated fatty acids that have one or more double bonds that hinder close packing. 2. Each cell in an organism has a plasma membrane that defines its boundaries, however the plasma membranes of different cell types show different fluidity. What factors determine the fluidity of the plasma membrane? This is defined by lipid composition and temperature. Fluidity of the membrane increases proportionately with an increase in the unsaturated fatty acids, short chain fatty acids or phospholipids. It also increases with an increase in temperature. Membrane fluidity is also know to decrease with an increase in the amount of cholesterol in the membrane. 3. When biomedical researchers design drugs that must enter cells to be effective, they often add methyl (-CH 3 ) groups, which make the drugs more likely to enter the cells. Why does this work? Plasma membrane is comprised of lipid bilayer with proteins embedded in it. Adding nonpolar, hydrophobic methyl groups (-CH 3 ) to the drug enhances the chances of the drug (which may otherwise be hydrophilic and hence incompatible for the hydrophobic atmosphere provided by the lipid bilayer) to cross the lipid bilayer and enter the cell to mediate its action.
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This note was uploaded on 03/12/2011 for the course BIO 7.012 taught by Professor Lander during the Fall '10 term at MIT.

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7.012_Section_1-solution_key_-2010 - Questions: Solution...

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