MCQs BIOCHEMISTRY: Structure of Peptides

1.
Hydrogen bonds in a-helices are

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
Answer & Explanation
Answer: Option D

2.
The peptide bond in proteins is

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
Answer & Explanation
Answer: Option C

3.
The molecular formula for glycine is C2H5O2N. What would be the molecular formula for a linear oligomer made by linking ten glycine molecules together by condensation synthesis?

A. C20H50O20N10 B. C20H32O11N10
C. C20H40O10N10 D. C20H68O29N10
Answer & Explanation
Answer: Option B

4.
Which of the following is an example of tertiary structure in a protein?

A. A multimeric protein
B. An a-helix
C. A P-pleated sheet
D. A globular domain
Answer & Explanation
Answer: Option D
5.
The peptide, Val-Lys-Glu-Met-Ser-Trp-Arg-Ala, was digested with cyanogen bromide (CNBr) to produce:

A. Val-Lys + Glu-Met-Ser + Trp-Arg-Ala
B. Val-Lys-Glu-Met-Ser-Trp + Arg-Ala
C. Val-Lys-Glu-Met + Ser-Trp-Arg-Ala
D. Val-Lys-Glu + Met-Ser-Trp-Arg-Ala
Answer & Explanation
Answer: Option C
6.
In deoxy hemoglobin (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
Answer & Explanation
Answer: Option A
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
Answer & Explanation
Answer: Option D
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
Answer & Explanation
Answer: Option D

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
Answer & Explanation
Answer: Option C
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
Answer & Explanation
Answer: Option B
11.
An oil drop with a polar coat is a metaphor referring to the three dimensional structure of

A. fibrous proteins
B. collagen
C. globular proteins
D. silk protein
Answer & Explanation
Answer: Option C

12.
What was the first protein whose complete tertiary structure was determined?

A. Lysozyme
B. Myoglobin
C. Pancreatic ribonuclease
D. Pancreatic DNase
Answer & Explanation
Answer: Option B

13.
The peptide bond in proteins is

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
Answer & Explanation
Answer: Option D

14.
In β-pleated sheet structures neighbouring

A. chains lie in a flat plane
B. neighboring residues are hydrogen bonded
C. neighboring chains are connected by a-helices
D. neighboring chains are hydrogen bonded
Answer & Explanation
Answer: Option D
15.
The same peptide, Val-Lys-Glu-Met-Ser-Trp-Arg-Ala. was digested with chymotrypsin to produce

A. Val-Lys + Glu-Met-Ser + Trp-Arg-Ala.
B. Val-Lys-Glu-Met-Ser-Trp + Arg-Ala.
C. Val-Lys-Glu-Met-Ser + Trp-Arg-Ala.
D. Val-Lys-Glu-Met + Ser-Trp-Arg-Ala.
Answer & Explanation
Answer: Option B