Biochemistry MCQ Quiz Hub

1. 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?
C20H50O20N10
C20H32O11N10
C20H40O10N10
C20H68O29N10

2. Which of the following is an example of tertiary structure in a protein?
A multimeric protein
An a-helix
A P-pleated sheet
A globular domain

3. The peptide, Val-Lys-Glu-Met-Ser-Trp-Arg-Ala, was digested with cyanogen bromide (CNBr) to produce:
Val-Lys + Glu-Met-Ser + Trp-Arg-Ala
Val-Lys-Glu-Met-Ser-Trp + Arg-Ala
Val-Lys-Glu-Met + Ser-Trp-Arg-Ala
Val-Lys-Glu + Met-Ser-Trp-Arg-Ala

4. In deoxy hemoglobin (Hb), the Fe (II) is coordinated to
four nitrogens of heme, the proximal His, and a water molecule
four nitrogens of heme and to a water molecule
two nitrogens of heme and to three His residues in Hb
two nitrogens of heme and to three water molecules

5. In the β-pleated sheet
hydrogen bonds are formed between the peptide bonds
adjacent polypeptide chains can either be parallel or antiparallel
the polypeptide chain is fully extended
all of the above

6. The Ramachandran Plot illustrates the fact that
the peptide bond is planar
the F & Y angles can assume any value in a peptide
the F & Y angles can assume only a single value in a protein
the F & Y angles can assume approximately three different values

7. The resonance structures that can be drawn for the peptide bond indicate that the peptide bond
is stronger than an ordinary single bond
has partial double bond character
both (a) and (b)
is still not completely understood

8. The major element of secondary structure in myoglobin and hemoglobin is
the P-strand
the a-helix
the reverse turn
All of these

9. An oil drop with a polar coat is a metaphor referring to the three dimensional structure of
fibrous proteins
collagen
globular proteins
silk protein

10. What was the first protein whose complete tertiary structure was determined?
Lysozyme
Myoglobin
Pancreatic ribonuclease
Pancreatic Dnase

11. The peptide bond in proteins is
planar, but rotates to three preferred dihedral angles
nonpolar, but rotates to three preferred dihedral angles
nonpolar, and fixed in a trans conformation
planar, and usually found in a trans conformation

12. In β-pleated sheet structures neighbouring
chains lie in a flat plane
neighboring residues are hydrogen bonded
neighboring chains are connected by a-helices
neighboring chains are hydrogen bonded

13. The same peptide, Val-Lys-Glu-Met-Ser-Trp-Arg-Ala. was digested with chymotrypsin to produce
Val-Lys + Glu-Met-Ser + Trp-Arg-Ala.
Val-Lys-Glu-Met-Ser-Trp + Arg-Ala.
Val-Lys-Glu-Met-Ser + Trp-Arg-Ala.
Val-Lys-Glu-Met + Ser-Trp-Arg-Ala.

14. Disulfide bonds most often stabilize the native structure of
extracellular proteins
dimeric proteins
hydrophobic proteins
intracellular proteins

15. Secondary structure in protein refers to
linear sequence of amino acids joined together by peptide bond
three dimensional arrangement of all amino acids in polypeptide chain
regular folding of regions of the polypeptide chain
protein made up of more than one polypeptide chain

16. Heme is the binding pocket of myoglobin and hemoglobin and is composed of
negatively charged residues
polar residues
hydrophobic residues
positively charged residues

17. What is the effect of a decrease in pH on hemoglobin oxygen affinity?
Decrease in oxygen affinity
Increase in oxygen affinity
No effect on oxygen affinity
Increase affinity in muscle cell otherwise decrease

18. What is the proportion of glycine residues in collagenous regions?
One-fourth
One-third
Half
One-tenth

19. Which of the following statements is incorrect?
Protein G contains both a-helix and P-sheet
Protein G contains only a-helix
Fatty acid binding protein contains largely P-sheet
Hemoglobin contains four sub-units

20. The oxygen binding curves of hemoglobin and myoglobin
allow maximum transfer of oxygen to the tissues
are a consequence of the quaternary structure of hemoglobin
Hydrogen bond
are identical

21. The nature of peptide bond can be best explained as
partial double bond
truly double bond
Hydrogen bond
Van der waals force

22. Which of the following statement is incorrect?
Hemoglobin and myoglobin are the two oxygen binding proteins
Hemoglobin transports O2 in the blood
Myoglobin stores O2 in muscles
None of the above

23. Which hemoglobin chain replaces the beta chain in embryonic hemoglobulin?
Delta
Epsilon
Gamma
Alfa

24. Hemoglobin has quaternary structure and is made up of
six polypeptide chains, two α-chains and four β-chains
two polypeptide chains, one α-chains and one β-chains
four polypeptide chains, two α-chains and two β-chains
five polypeptide chains, two α-chains and three β-chains

25. Peptides in the fully extended chain conformation
have Y = F = 180°
do not occur in nature
also have a cis geometry in their peptide bonds
are equivalent to the (3-sheet structure

26. The oxygen in hemoglobin and myoglobin is bound to
the iron atom in the heme group
the nitrogen atoms on the heme
histidine residues in the protein
lysine residues in the protein

27. Which of the three subunits of the G proteins binds GDP and GTP?
Alpha
Beta
Gamma
Delta

28. If the F and Y angles of each peptide unit in a protein are known, which of the following may also be determined?
Complete secondary structure
Complete tertiary structure
Complete quaternary structure
Thermodynamic stability

29. The different orders of protein structure are determined by all of the following bond types except
peptide bonds
phospho-diester bonds
disulfide bridges
hydrogen bonds

30. The heme is held in place by a bond between
the Fe2+ and cysteine
the Fe3+ and histidine
the Fe3+ and cysteine
the Fe2+ and histidine

31. Unpaired H-bond donors and acceptors are found in the hydrophobic core of a protein
only at the ends of a-helices
only at the turns connecting p-strands
only on Pro residues
rarely

32. For the unfolding reaction of Protein G, ΔH° =210.6 kJ/mol, this means that
unfolding is favored enthalpically
folding is favored enthalpically
the entropy is positive at all temperatures
the entropy is negative at all temperatures

33. Attractive Vander Waals forces occur between
apolar molecules in the liquid state
any pair of nearby atoms
polar molecules in the solid state
only if other forces are less favorable

34. Which of the following forces is the most favorable for protein folding?
Conformational entropy
Hydrophobic Interactions
Vander Waals interactions
Hydrogen bonds

35. At the midpoint of a temperature transition curve,
half of the protein is denatured
Keq = 1.0 and ΔG = 0
[Native] = [Unfolded]
All of these

36. Which of the following is the most correct?
Charged amino acids are never buried in the interior of a protein
Charged amino acids are seldom buried in the interior of a protein
All hydrophobic amino acids are buried when a protein folds
Tyrosine is only found in the interior of proteins

37. Which of the following forces is the most unfavorable for protein folding?
Conformational entropy
Hydrophobic interactions
Vander Waals interactions
Electrostatic interactions

38. Since ΔG° = -RTlnK
a 10-fold increase in K decreases ΔG° by about 10-fold
a 10-fold decrease in K decreases ΔG° by about 2.3*RT
a 10-fold increase in K decreases ΔG° by about 2.3*RT
a 10-fold decrease in K increases ΔG° by about 10-fold

39. The correlation between free energy ΔG transfer between the aqueous/organic phases and the surface area of amino acid residues
reflects the reduction in solvent-accessible area during protein folding
is only meaningful for the polar amino acids
ignores the important contribution of the peptide bond
is similar to effects seen with SDS denaturation

40. If the egg white protein, ovalbumin, is denatured in a hard-boiled egg, then which of the following is least affected?
The primary structure of ovalbumin
The secondary structure of ovalbumin
The tertiary structure of ovalbumin
The quaternary structure of ovalbumin

41. Buried hydrophobic side chains in a globular protein fit into a hole formed by the side chains of
1-3 other amino acids
5-7 other amino acids
9-12 other amino acids
13-15 other amino acids

42. In an SDS-PAGE
proteins are denatured by the SDS
proteins have the same charge-to-mass ratio
smaller proteins migrate more rapidly through the gel
all of the above

43. Proteins can be visualized directly in gels by
staining them with the dye
using electron microscope only
measuring their molecular weight
none of these

44. In SDS-PAGE, the protein sample is first
treated with a reducing agent and then with anionic detergent followed by fractionation by electrophoresis
fractionated by electrophoresis then treated with an oxidizing agent followed by anionic detergent.
treated with a oxidizing agent and then with anionic detergent followed by fractionation by electrophoresis
none of the above

45. Electrophoresis of histones and myoglobin under non-denaturing conditions (pH = 7.0) results in
both proteins migrate to the anode
histones migrate to the anode and myoglobin migrates to the cathode
histones migrate to the cathode and myoglobin migrates to the anode
both proteins migrate to the cathode

46. In isoelectric focusing, proteins are separated on the basis of their
relative content of positively charged residue only
relative content of negatively charged residue only
size
relative content of positively and negatively charged residue

47. In a gel filtration column
smaller proteins enter the beads more readily
large proteins elute first
both (a) and (b)
large proteins enter the beads more readily

48. In a native PAGE, proteins are separated on the basis of
net negative charge
net charge and size
net positive charges size
net positive charge

49. The subunit molecular weight as well as the number of subunits in the quaternary structure can be determined by
SDS-PAGE electrophoresis
gel filtration chromatography
combining information from (a)and (b)
isoelectric focusing

50. Proteins are separated in an SDS-PAGE experiment on the basis of their
positively charged side chains
molecular weight
negatively charged side chains
different isoelectric points

51. Enzyme-driven metabolic pathways can be made more efficient by
concentrating enzymes within specific cellular compartments
grouping enzymes into free-floating, multienzyme complexes
fixing enzymes into membranes so that they are adjacent to each other
All of the above

52. Which of the following (s) is/are serine proteases?
Chymotrypsin
Trypsin
Elastase
all of these

53. Which of the following statements about enzymes or their function is true?
Enzymes do not alter the overall change in free energy for a reaction
Enzymes are proteins whose three-dimensional form is key to their function
Enzymes speed up reactions by lowering activation energy
All of the above

54. Tryprotophan synthetase of E.coli, a typical bifunctional oligomeric enzyme consist of
a protein designated A
two proteins designated A and B
a protein A and one-subunit a
a protein designated B

55. What is the specificity of the Clostripain protease?
It cleave after Arg residues
It cleave after His residues
It cleave after Lys residues
None of the above

56. The proteolysis rate enhancement by chymotrypsin (~1010 folds) corresponds to a reduction in activation energy of about
40 kJ/mol
49 kJ/mol
58 kJ/mol
88 kJ/mol

57. Which of the following is false statement with regard to comparison between Serine and HIV proteases?
Both use nucleophilic attack to hydrolyze the peptide bond
Both require water to complete the catalytic cycle
Both forms an acyl-enzyme intermediate
Both show specificity for certain amino acid sequences

58. In the enzyme-catalyzed reaction shown below, what will be the effect on substances A, B, C, and D of inactivating the enzyme labeled E2? A ---(E1)---> B ---(E2)---> C ---(E3)--->
A, B, C, and D will all still be produced
A, B, and C will still be produced, but not D
A and B will still be produced, but not C or D
A will still be produced, but not B, C, or D

59. The nucleophile in serine proteases is
Serine
water
both (a) and (b)
Asparagine

60. The role of Asp 102 and His 57 during trypsin catalysis is to
neutralize the charge on the other's side chain
keep the specificity pocket open
function as a proton shuttle
clamp the substrate into the active site

61. The cleavage specificity of trypsin and chymotrypsin depend in part on the
proximity of Ser 195 to the active site or specificity pocket
size, shape, and charge of the active site or specificity pocket
presence of a low-barrier hydrogen bond in the active site or specificity pocket
absence of water in the active site

62. The E.coli pyruvic acid dehydrogenase complex is reported to
decatalyze the oxidation of pyruvic acid to acetyl Co A and CO2
Catalyze the oxidation of pyruvic acid to acetyl Co A and CO2
retard the reduction of pyruvic acid to acetyl Co A and CO2
Catalyze the reduction of pyruvic acid to acetyl Co A and CO

63. Which of the common features are shared between serine and aspartate proteases?
Both require water to complete the catalytic cycle
Both use a base to activate the nucleophile
Both show specificity for certain amino acid sequences
All of the above

64. Before they can react, many molecules need to be destabilized. This state is typically achieved through
changing the three-dimensional shape of the molecule
oxidizing the molecules by removing electrons
changing the reaction from a biosynthetic to a catabolic pathway
the input of a small amount of activation energy

65. Common feature in all serine proteases is a
hydrophobic specificity pocket
hydrophilic specificity pocket
cluster of reactive serine residues
single reactive serine residue

66. How is the enzyme COX-1 important in human health?
It helps to transport carbon dioxide in the blood
It is critical for the biosynthesis of DNA
It is a chemical derivative of aspirin
It catalyzes the production of hormones that maintain the stomach lining

67. For specific antigen recognition by T cells,
antigen is bound by a T cell membrane antibody
denaturation of antigen does not reduce epitope recognition
MHC molecules are not required
antigen exposure during T cell maturation is required

68. Antigen, when injected in the body activates its specific lymphocytes in the
blood circulation
draining lymph nodes
MALT (mucosa associated
spleen lymphoid tissue

69. A molecule that can be covalently linked to a non-immunogenic antigen to make it an immunogen is called a (n)
adjuvant
carrier
hapten
mitogen