1. Do you expect the native structure of a large protein to be the only stable 3
ID: 18057 • Letter: 1
Question
1. Do you expect the native structure of a large protein
to be the only stable 3-dimensional structure possible
for a given amino acid sequence? Explain.
a. Yes, the primary structure has a 1-to-1 correspondence
with the tertiary structure.
b. No, although the native structure has a low free energy,
there may be other conformations at other minima of free
energy.
c. Yes, because all proteins have chaperones that assist their
folding into only the native conformation.
d. No, many conformations are possible because protein
folding in nature is essentially a random process.
2. The molecule 2,3-bisphospho-D-glycerate (2,3BPG) raises the P50 of hemoglobin. What effect does this have?
a. Increases the binding of CO to hemoglobin.
b. Allows more efficient release of O2 to the tissues.
c. Decreases the pH dependence of the oxygen binding.
d. Raises the effective concentration of oxygen in red blood cells.
e. Oxidizes the iron ion in the heme.
3. Based strictly on Pauling’s definition of alpha helices and beta sheets, can proline fit in the middle of an alpha helix.
A. True, Proline’s compact side chain allows for better helical packing.
B. False, the charged COO- group on its side chain will hydrogen bond to its main-chain –NH group.
C. True, Proline is an amino acid and amino acids form helices.
D. False, Proline lacks the main-chain –NH group needed for hydrogen bonding in the -helix
4. The treatment of a protein that has disulfide bonds with ______________ produces Cys residues with free sulfhydryl groups.
A. A. Trypsin
B. Cyanogen bromide (CNBr)
C. -mercaptoethanol
D. Edman’s reagent
Explanation / Answer
1b. No, although the native structure has a low free energy, there may be other conformations at other minima of free energy. 2b. Allows more efficient release of O2 to the tissues. 3D. False, Proline lacks the main-chain –NH group needed for hydrogen bonding in the a-helix 4C. ß-mercaptoethanol
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