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Study Questions - BIS 102, Prof. C. Gasser 42 BioSci 102...

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BIS 102, Prof. C. Gasser 42 BioSci 102 Sample Study Problems for Second Midterm 1. The aggregation of platelets in blood to form a plug on an injured surface of a blood vessel occurs after sequential activation of at least ten different enzymes which are normally present in blood as inactive precursors. Human platelets are composed of one major phospholipid, 1-stearoyl-2-arachidonyl phosphatidylinositol. The components of the phospholipid are stearic acid (18:0), arachidonic acid (20:4 all cis 5,8,11,14 ), glycerol, phosphate, and inositol (structure shown below). OH OH OH HO OH OH 6 5 4 3 2 1 Inositol a) In the space below, draw the complete structure of the phospholipid 1-stearoyl-2- arachidonyl phosphatidylinositol, given that the linkage of inositol to the phosphatidate involves the hydroxyl group on carbon 1 of inositol. (SHOW ALL BONDS). b) Sonication of the phospholipid described in part a) would most likely lead to the formation of (micelles, liposomes , two insoluble liquid phases). CIRCLE BEST ANSWER. Based on your answer, provide a diagrammatic description of the structures, if any, that would form upon sonication of this phospholipid. With your answer, please identify which of the components of the phospholipid will be exposed to the aqueous environment. Inositol-PO 4 exposed to H 2 O Hydrophobic fatty acyl tails, sequestered from H 2 O H 2 O H 2 O
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BIS 102, Prof. C. Gasser 43 2. A region of a globular protein has the sequence GRAKSR. a) Which of the following other regions of the same protein would be most likely to participate in ionic bonding with the above region? Give the reason for your answer. A) WLIFTV B) NEQKRL C) NEQDHD • D) VILALL Reason?- GRAKSR contains three amino acids that are positively charged at neutral pH (R and K). Peptide C has three negatively charged amino acids (D and E). These two peptides could therefore form strong salt bridges. b) Which two of the regions in a) could be held together tightly in the internal part of the protein by hydrophobic interactions? Give a reason for your answer. A and D Reason? These two peptides consist mostly of very hydrophobic amino acids. They would therefore be likely to reside in the inside of the intact protein, and if they are adjacent to each other would be held together by hydrophobic interactions. 3. Name and draw the structural formulas for three amino acids that are not
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Study Questions - BIS 102, Prof. C. Gasser 42 BioSci 102...

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