320Fall2010Homework1_key - Cell Biology(BIO 320 Fall 2010...

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Cell Biology (BIO 320), Fall 2010, Dr. Bushart Homework set #1 key 1. Dissolving solid urea in water is an endothermic reaction (+ΔH) yet it still occurs spontaneously at room temperature. a. In the context of the free energy equation, how would heating the water help this process? Higher temperatures increase the subtracted value of “T Δ S, which needs to be larger than the value of Δ H in order for the reaction to be spontaneous. b. Even at room temperature this process will occur. How can we explain this in terms of the free energy equation? Note that you should be able to answer this without looking up the specific details of how urea dissolves (which does help explain it too). Solid urea is ordered. Dissolved urea is going to be disordered since it is mixed up with water. The change in entropy is therefore favorable even if H is not. 2. Proteins are found in many different environments within the cell. a. Which classes of amino acid side chains would you expect to be on the outside of a properly folded water-soluble protein? Explain. Any of the side chains that interact favorably with water should be on the outside: acidic, basic, polar. If it is water soluble, it must be able to interact with water through hydrogen bonding. (The core of the protein may consist of nonpolar amino acids to increase stability through their clustering via hydrophobic forces.) b.
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This note was uploaded on 09/12/2010 for the course BIO 320 taught by Professor Staff during the Fall '08 term at University of Texas.

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320Fall2010Homework1_key - Cell Biology(BIO 320 Fall 2010...

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