Exam I - Fall 2006 (student answers)

Exam I Fall 2006 - Exam I Fall 2006 Answers in red have been debated by many and still a solid answer has yet come TRUE/FALSE 1 In protein x-ray

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Answers in red have been debated by many, and still a solid answer has yet come. TRUE/FALSE 1) In protein x-ray crystallography, the level of resolution at which the C, N, and O atoms of an alpha helix start to be resolved is 5 Angstroms. False, 1.5 Angstroms is the length of an amino acid. 5 Angstroms is not small enough. 2) The crystals analyzed by x-ray diffraction contain arrays of tightly packed protein molecules held together by non-covalent interactions between the proteins. True 3) The loop of amino acids joining the c-terminus of a beta strand to the n-terminus of the alpha helix in a beta-alpha-beta motif in a globular protein often contains amino acids involved in catalysis. True 4) Hydrophobic interactions between proteins in aqueous solution are favored because the number of ordered water molecules surrounding the proteins is maximized, giving the system greater thermodynamic stability. False , ordering is minimized 5) The two substrates that participate in the formation of a peptide bond in the solid phase synthesis of a peptide are the Fmoc-derivatized carboxy terminal amino acid and a dicyclohexylcarbodimide-activated amino acid. False, Fmoc is on the N-terminus. 6) The amino acid sequence of a globular protein determines the protein’s tertiary structure. False 7) Peptide prolyl isomerase catalyzes trans cis isomerism of proline residues, and therefore promotes formation of the beta-turns needed for a protein to adopt its folded conformation. True 8) V, L, M, W, and F are all classified as hydrophobic amino acids. False, W can be an H- bond donor through N-H group. 9) Sodium dodecyl sulfate polyacrylamide gel electrophoresis separates proteins according to their charge. False 10) The alpha-carboxyl group of a free amino acid has a higher pKa than the alpha-carboxyl group of a peptide (False) because the charge of the unprotonated form of the alpha- carboxyl group in the free amino acid can be stabilized by the charge of the protonated alpha-amino group (true). Multiple Choice
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This note was uploaded on 02/09/2009 for the course MCB 354 taught by Professor Spees during the Spring '09 term at University of Illinois, Urbana Champaign.

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Exam I Fall 2006 - Exam I Fall 2006 Answers in red have been debated by many and still a solid answer has yet come TRUE/FALSE 1 In protein x-ray

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