Structure and Properties of Peptides – Section 1

6. In deoxyhemoglobin (Hb), the Fe (II) is coordinated to

A. four nitrogens of heme, the proximal His, and a water molecule
B. four nitrogens of heme and to a water molecule
C. two nitrogens of heme and to three His residues in Hb
D. two nitrogens of heme and to three water molecules

Correct Answer: A. four nitrogens of heme, the proximal His, and a water molecule

7. In the β-pleated sheet

A. hydrogen bonds are formed between the peptide bonds
B. adjacent polypeptide chains can either be parallel or antiparallel
C. the polypeptide chain is fully extended
D. all of the above

Correct Answer: D. all of the above

8. The Ramachandran plot illustrates the fact that

A. the peptide bond is planar
B. the F & Y angles can assume any value in a peptide
C. the F & Y angles can assume only a single value in a protein
D. the F & Y angles can assume approximately three different values

Correct Answer: D. the F & Y angles can assume approximately three different values

9. The resonance structures that can be drawn for the peptide bond indicate that the peptide bond

A. is stronger than an ordinary single bond
B. has partial double bond character
C. both (a) and (b)
D. is still not completely understood

Correct Answer: C. both (a) and (b)

10. The major element of secondary structure in myoglobin and hemoglobin is

A. the P-strand
B. the a-helix
C. the reverse turn
D. All of these

Correct Answer: B. the a-helix

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