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BIO 2960 HW 3 - Problem Set#3 KEY Biology 2960 Spring 2012...

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Problem Set #3 KEY Biology 2960 Spring 2012 1. Which one of each of the following pairs of amino acids has higher solubility in water? a) Ala & Leu, b) Tyr & Phe, c) Ser & Ala, d) Trp & His. Explain your answer. Structures of R groups are listed at the end of this problem set. Ala’is’more’soluble’than’Leu’because’it’is’less’hydrophobic’without’a’ hydrophobic’R’group. ’ Tyr’is’more’soluble’than’Phe’because’it’is’more’hydrophilic’due’to’the’ presence’of’OH. ’ Ser’is’more’soluble’than’Ala’because’it’is’more’hyd rophilic’due’to’the’ presence’of’OH. ’ His’is’more’soluble’than’Trp’because’it’is’more’hydrophilic’due’to’the’ positive’charge. 2. Explain why a fatty acid, oleic acid (18 carbon, one cis double bond), has lower melting point than stearic acid, which has the same number carbons but is saturated. The’presence’of’cis -double’bond’will’make’oleic’acid’bent,’hence’less’ tightly’packed’and’more’fluid.’Therefore,’it’stays’as’liquid’at’lower’ temperature.’ 3. What is bioethanol (cellulosic ethanol)? How could it be made? Cellulosic’ethanol’is’made’by’fer mentation’of ’sugars ’(primarily’ glucose)’generated’from’the’hydrolysis’of’cellulosic’agricultural’wastes’ such’as’corn’stover’and’wheat/rice’straws.’The’cellulosic’raw’ materials’are’first’hydrolyzed’by’cellulases’fro m’microbes’capable’of’ utilizing’cellulose.’The’fermentation’process’is’similar’to’the’brewing’ process’that’is’already’well’established’in’industry.’ ’ ’ 4. Assume you have a protein that is 44 kD (kilo Dalton) that is composed of two equal length α -helical domains. How many Angstroms long is each α - helix? Each α -helix is ~22 kD with 200 amino acids 22 kD / 0.11 kD) = 200 AA Length of each α -helix: 200 AA x 1.5 Angstroms (Å)/AA = 300 Å 5. Comparisons among the primary amino acid sequences of related proteins from different organisms highlights highly conserved amino acids. Conserved amino acids are retained through evolutionary time because these residues are important for protein function. Glycine is one amino acid that is often found to be highly conserved. Provide an explanation for this observation based on your understanding of glycine’s structure.
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