Exam 2 Fall 07 Key MCB181R Dr. Jorstad

Exam 2 Fall 07 Key MCB181R Dr. Jorstad - MCB 181R, Fall...

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MCB 181R, Fall 2007 Instructor: Dr. S. Jorstad Exam II DETAILED KEY For multiple choice questions (each worth 3 points), bubble all correct answers (there may be more than one); there is a 1 point penalty for incorrect answer choices. For short essays (each worth 5 points): confine your answers to the space provided on the scansheet. Writing outside those margins will adversely affect the machine-scoring of your exam. You may use bulleted points to express yourself, as long as your meaning is clear. 1. Which of the following statements is/are correct with regard to the processes by which polymers are assembled and disassembled? a. Polymers are assembled by enzymes. * b. Polymers are disassembled by enzymes. * c. A hydrolysis reaction is used to build polymers, and a water molecule is released. this statement describes a condensation rxn d. Condensation reactions release energy. condensation rxns are building rxns (anabolic, endergonic), which require energy e. Hydrolysis of polymers releases energy. * (catabolic, exergonic) 2. Pictured below is an amino acid, with its R-group sticking up, and its “backbone” along the bottom. Which of the following statements is/are correct about this amino acid? a. We can tell it is classified as a polar amino acid because of the positive charge on the amino group (NH 3 ) and the negative charge on the oxygens that make up the carboxyl group. This describes the backbone; the amino acid is classified as polar/nonpolar based on properties of its R-group . b. We can tell it is classified as a non-polar amino acid because of the multiple carbon-hydrogen bonds in the R-group. * hydrocarbon tail = equal sharing of electrons = non-polar/hydrophobic c. If this amino acid were part of a transmembrane protein, it would be located in the part of the protein sticking out into either the cytoplasm or the extracellular environment. this situation would require POLAR amino acids d. If this amino acid were part of a transmembrane protein, it would be located in the part of the protein that interacts with the lipid interior (hydrophobic) of the membrane. * e. This is not an amino acid; it is a nucleotide. 3. The function of a protein is dependent on its exact 3-dimensional (3-D) shape; any change in the shape will alter the protein’s function. Protein shape is determined in part by
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a. the exact sequence of nucleotides that are linked up covalently in the primary structure of the protein. should be “amino acids” b. weak H-bonds that form between different amino acids in the polymer, and that twist the polymer into α -helices, or fold it into β -pleated sheets. * c. covalent bonds that hold the polypeptide in its precisely folded 3-D tertiary structure. it is WEAK bonds that do this d. hydrophobic effects that drive the hydrophobic amino acids into the interior of the 3-D shape. * e. phosphodiester bonds (these exist in nucleic acids) that hold the multiple subunits of the quaternary structure solidly together. and it is weak bonds that do
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This test prep was uploaded on 04/14/2008 for the course MCB 181 taught by Professor Jorstad during the Fall '07 term at University of Arizona- Tucson.

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Exam 2 Fall 07 Key MCB181R Dr. Jorstad - MCB 181R, Fall...

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