STRUCTURE and PROPERTIES of PEPTIDES Multiple Choice Questions :-
1. Disulfide bonds most often stabilize the native structure of
A. extracellular proteins
B. dimeric proteins
C. hydrophobic proteins
D. intracellular proteins
Answer: A
2. Secondary structure in protein refers to
A. linear sequence of amino acids joined together by peptide bond
B. three dimensional arrangement of all amino acids in polypeptide chain
C. regular folding of regions of the polypeptide chain
D. protein made up of more than one polypeptide chain
Answer: C
3. Heme is the binding pocket of myoglobin and hemoglobin and is composed of
A. negatively charged residues
B. polar residues
C. hydrophobic residues
D. positively charged residues
Answer: C
4. What is the effect of a decrease in pH on hemoglobin oxygen affinity?
A. Decrease in oxygen affinity
B. Increase in oxygen affinity
C. No effect on oxygen affinity
D. Increase affinity in muscle cell otherwise decrease
Answer: A
5. What is the proportion of glycine residues in collagenous regions?
A. One-fourth
B. One-third
C. Half
D. One-tenth
Answer: B
6. Which of the following statements is incorrect?
A. Protein G contains both a-helix and P-sheet
B. Protein G contains only a-helix
C. Fatty acid binding protein contains largely P-sheet
D. Hemoglobin contains four sub-units
Answer: B
7. The oxygen binding curves of hemoglobin and myoglobin
A. allow maximum transfer of oxygen to the tissues
B. are a consequence of the quaternary structure of hemoglobin
C. both (a) and (b)
D. are identical
Answer: C
8. The nature of peptide bond can be best explained as
A. partial double bond
B. truly double bond
C. Hydrogen bond
D. Van der waals force
Answer: A
9. Which of the following statement is incorrect?
A. Hemoglobin and myoglobin are the two oxygen binding proteins
B. Hemoglobin transports O2 in the blood
C. Myoglobin stores O2 in muscles
D. None of the above
Answer: D
10. Which hemoglobin chain replaces the beta chain in embryonic hemoglobulin?
A. Delta
B. Epsilon
C. Gamma
D. Alfa
Answer: B
STRUCTURE and PROPERTIES of PEPTIDES Objective type Questions with Answers
11. Hemoglobin has quaternary structure and is made up of
A. six polypeptide chains, two a-chains and four ß-chains
B. two polypeptide chains, one a-chains and one ß-chains
C. four polypeptide chains, two a-chains and two ß-chains
D. five polypeptide chains, two a-chains and three ß-chains
Answer: C
12. When pO2 = Kd of myoglobin, the fractional saturation (YO2) is about
A. 0.1
B. 0.5
C. 0.9
D. 1.7
Answer: B
13. Peptides in the fully extended chain conformation
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
Answer: A
14. The oxygen in hemoglobin and myoglobin is bound to
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
Answer: A
15. Which of the three subunits of the G proteins binds GDP and GTP?
A. Alpha
B. Beta
C. Gamma
D. Delta
Answer: A