Structure and Properties of Peptides problems
- 1. The peptide bond in proteins is
Options- A. planar, but rotates to three preferred dihedral angles
- B. nonpolar, but rotates to three preferred dihedral angles
- C. nonpolar, and fixed in a trans conformation
- D. planar, and usually found in a trans conformation Discuss
Correct Answer: planar, and usually found in a trans conformation
- 2. The resonance structures that can be drawn for the peptide bond indicate that the peptide bond
Options- 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 Discuss
Correct Answer: both (a) and (b)
- 3. Hydrogen bonds in a-helices are
Options- A. more numerous than Vander Waals interactions
- B. not present at Phe residues
- C. analogous to the steps in a spiral staircase
- D. roughly parallel to the helix axis Discuss
Correct Answer: roughly parallel to the helix axis
- 4. The peptide bond in proteins is
Options- A. only found between proline residues
- B. usually cis unless proline is the next amino acid
- C. usually trans unless proline is the next amino acid
- D. is planar because of steric hinderance Discuss
Correct Answer: usually trans unless proline is the next amino acid
- 5. The oxygen in hemoglobin and myoglobin is bound to
Options- A. the iron atom in the heme group
- B. the nitrogen atoms on the heme
- C. histidine residues in the protein
- D. lysine residues in the protein Discuss
Correct Answer: the iron atom in the heme group
- 6. The nature of peptide bond can be best explained as
Options- A. partial double bond
- B. truly double bond
- C. Hydrogen bond
- D. Van der waals force Discuss
Correct Answer: partial double bond
- 7. Peptides in the fully extended chain conformation
Options- A. have Y = F = 180°
- B. do not occur in nature
- C. also have a cis geometry in their peptide bonds
- D. are equivalent to the (3-sheet structure Discuss
Correct Answer: have Y = F = 180°
- 8. Heme is the binding pocket of myoglobin and hemoglobin and is composed of
Options- A. negatively charged residues
- B. polar residues
- C. hydrophobic residues
- D. positively charged residues Discuss
Correct Answer: hydrophobic residues
- 9. The different orders of protein structure are determined by all of the following bond types except
Options- A. peptide bonds
- B. phospho-diester bonds
- C. disulfide bridges
- D. hydrogen bonds Discuss
Correct Answer: phospho-diester bonds
- 10. An oil drop with a polar coat is a metaphor referring to the three dimensional structure of
Options- A. fibrous proteins
- B. collagen
- C. globular proteins
- D. silk protein Discuss
Correct Answer: globular proteins
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