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Unformatted text preview: Biochemistry 460, Exam #1A NAME Key for version A- version B is the same questions with the multiple choice in a different order February 13, 2009 Page 1 of 6 Total _________ 1- A tetrapeptide structure is shown below: A. (4 pts) Circle a group of 6 atoms in the tetrapeptide that are coplanar ( all in the same plane),excluding atoms in cyclic structures. There is more than one correct answer, but circle only 6 atoms total ; if you circle more than 6 atoms, the grader will assume you mean the first 6 atoms you circle starting from the left. See circled atoms above; ANY 6-atom peptide group from one C to the next C , i.e., C -C(O)-NH-C , was OK -- there were 3 such groups to choose from. B. (4 pts) The structure is drawn in a certain state of ionization. Under which of the following pH conditions would this peptide exist predominantly in the state of ionization shown above? a) pH 10 b) pH 7.5 c) pH 5 d) pH 1 (pH must be above the pKa of the -amino group for that group to be in its neutral, conjugate base, state) C. (4 pts) Which residue (A, B, C or D) has an R group that can be involved in TWO (2 ) hydrogen bonds in the form shown above? residue C (Asn) or A __ D. (4 pts) Which residue (A, B, C or D) has the most hydrophobic R group? __residue D (Phe)__ E. (4 pts) Draw one clear ARROW ( - ) to any ONE of the peptide bonds in this structure. Draw only one arrow. If you draw more than one, the grader will assume you mean the arrow closest to left end. Any one of the 3 peptide bonds (3 arrows above) was O.K Biochemistry 460, Exam #1A NAME Key for version A- version B is the same questions with the multiple choice in a different order February 13, 2009 Page 2 of 6 Total _________ 2- The structure of the enzyme citrate synthase, a homodimer, is shown below. A. (3 pts) What is the principal type of secondary structure seen in the structure above? __ helix__ B. (3 pts) What type of axis of rotational symmetry is apparent in this structure? _____2-fold________ C. (6 pts) Name 3 of the 4 types of noncovalent interactions that might be expected to stabilize the tertiary and quaternary structures of a protein such as this one. (Disulfide bonds are covalent bonds, so don't give that as an answer.) ionic bonds (or charge-charge, or salt links; hydrogen bonds, van der Waals interactions, hydrophobic interactions D. (4 pts) What principles would dictate the folding of this globular protein in aqueous solution? hydrophobic residue move away from water to the core (i.e. minimizing solvent accessible area): maximize hydrogen bonding; chiral effects, disulfide bonds, ionic interactions (FULL CREDI T for any two) We also accepted primary structure, and - G, 3. In a muscle cell, when the ATP required to provide the energy for muscle contraction is depleted, another &quot;energy storage&quot; compound, creatine phosphate, can provide the energy to produce ATP from ADP in the following reaction: ADP + creatine phosphate...
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This note was uploaded on 05/06/2010 for the course BIOC 460 taught by Professor Ziegler during the Spring '07 term at Arizona.
- Spring '07