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Biochemistry MCQS PAPER SET 11
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Biochemistry MCQS PAPER SET 11
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?
A
C20H50O20N10
B
C20H32O11N10
C
C20H40O10N10
D
C20H68O29N10
2
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
3
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
4
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
5
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
6
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
7
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
8
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
9
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
10
What was the first protein whose complete tertiary structure was determined?
A
Lysozyme
B
Myoglobin
C
Pancreatic ribonuclease
D
Pancreatic Dnase
11
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
12
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
13
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.
14
Disulfide bonds most often stabilize the native structure of
A
extracellular proteins
B
dimeric proteins
C
hydrophobic proteins
D
intracellular proteins
15
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
16
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
17
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
18
What is the proportion of glycine residues in collagenous regions?
A
One-fourth
B
One-third
C
Half
D
One-tenth
19
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
20
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
Hydrogen bond
D
are identical
21
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
22
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
23
Which hemoglobin chain replaces the beta chain in embryonic hemoglobulin?
A
Delta
B
Epsilon
C
Gamma
D
Alfa
24
Hemoglobin has quaternary structure and is made up of
A
six polypeptide chains, two α-chains and four β-chains
B
two polypeptide chains, one α-chains and one β-chains
C
four polypeptide chains, two α-chains and two β-chains
D
five polypeptide chains, two α-chains and three β-chains
25
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
26
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
27
Which of the three subunits of the G proteins binds GDP and GTP?
A
Alpha
B
Beta
C
Gamma
D
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?
A
Complete secondary structure
B
Complete tertiary structure
C
Complete quaternary structure
D
Thermodynamic stability
29
The different orders of protein structure are determined by all of the following bond types except
A
peptide bonds
B
phospho-diester bonds
C
disulfide bridges
D
hydrogen bonds
30
The heme is held in place by a bond between
A
the Fe2+ and cysteine
B
the Fe3+ and histidine
C
the Fe3+ and cysteine
D
the Fe2+ and histidine
31
Unpaired H-bond donors and acceptors are found in the hydrophobic core of a protein
A
only at the ends of a-helices
B
only at the turns connecting p-strands
C
only on Pro residues
D
rarely
32
For the unfolding reaction of Protein G, ΔH° =210.6 kJ/mol, this means that
A
unfolding is favored enthalpically
B
folding is favored enthalpically
C
the entropy is positive at all temperatures
D
the entropy is negative at all temperatures
33
Attractive Vander Waals forces occur between
A
apolar molecules in the liquid state
B
any pair of nearby atoms
C
polar molecules in the solid state
D
only if other forces are less favorable
34
Which of the following forces is the most favorable for protein folding?
A
Conformational entropy
B
Hydrophobic Interactions
C
Vander Waals interactions
D
Hydrogen bonds
35
At the midpoint of a temperature transition curve,
A
half of the protein is denatured
B
Keq = 1.0 and ΔG = 0
C
[Native] = [Unfolded]
D
All of these
36
Which of the following is the most correct?
A
Charged amino acids are never buried in the interior of a protein
B
Charged amino acids are seldom buried in the interior of a protein
C
All hydrophobic amino acids are buried when a protein folds
D
Tyrosine is only found in the interior of proteins
37
Which of the following forces is the most unfavorable for protein folding?
A
Conformational entropy
B
Hydrophobic interactions
C
Vander Waals interactions
D
Electrostatic interactions
38
Since ΔG° = -RTlnK
A
a 10-fold increase in K decreases ΔG° by about 10-fold
B
a 10-fold decrease in K decreases ΔG° by about 2.3*RT
C
a 10-fold increase in K decreases ΔG° by about 2.3*RT
D
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
A
reflects the reduction in solvent-accessible area during protein folding
B
is only meaningful for the polar amino acids
C
ignores the important contribution of the peptide bond
D
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?
A
The primary structure of ovalbumin
B
The secondary structure of ovalbumin
C
The tertiary structure of ovalbumin
D
The quaternary structure of ovalbumin
41
Buried hydrophobic side chains in a globular protein fit into a hole formed by the side chains of
A
1-3 other amino acids
B
5-7 other amino acids
C
9-12 other amino acids
D
13-15 other amino acids
42
In an SDS-PAGE
A
proteins are denatured by the SDS
B
proteins have the same charge-to-mass ratio
C
smaller proteins migrate more rapidly through the gel
D
all of the above
43
Proteins can be visualized directly in gels by
A
staining them with the dye
B
using electron microscope only
C
measuring their molecular weight
D
none of these
44
In SDS-PAGE, the protein sample is first
A
treated with a reducing agent and then with anionic detergent followed by fractionation by electrophoresis
B
fractionated by electrophoresis then treated with an oxidizing agent followed by anionic detergent.
C
treated with a oxidizing agent and then with anionic detergent followed by fractionation by electrophoresis
D
none of the above
45
Electrophoresis of histones and myoglobin under non-denaturing conditions (pH = 7.0) results in
A
both proteins migrate to the anode
B
histones migrate to the anode and myoglobin migrates to the cathode
C
histones migrate to the cathode and myoglobin migrates to the anode
D
both proteins migrate to the cathode
46
In isoelectric focusing, proteins are separated on the basis of their
A
relative content of positively charged residue only
B
relative content of negatively charged residue only
C
size
D
relative content of positively and negatively charged residue
47
In a gel filtration column
A
smaller proteins enter the beads more readily
B
large proteins elute first
C
both (a) and (b)
D
large proteins enter the beads more readily
48
In a native PAGE, proteins are separated on the basis of
A
net negative charge
B
net charge and size
C
net positive charges size
D
net positive charge
49
The subunit molecular weight as well as the number of subunits in the quaternary structure can be determined by
A
SDS-PAGE electrophoresis
B
gel filtration chromatography
C
combining information from (a)and (b)
D
isoelectric focusing
50
Proteins are separated in an SDS-PAGE experiment on the basis of their
A
positively charged side chains
B
molecular weight
C
negatively charged side chains
D
different isoelectric points
51
Enzyme-driven metabolic pathways can be made more efficient by
A
concentrating enzymes within specific cellular compartments
B
grouping enzymes into free-floating, multienzyme complexes
C
fixing enzymes into membranes so that they are adjacent to each other
D
All of the above
52
Which of the following (s) is/are serine proteases?
A
Chymotrypsin
B
Trypsin
C
Elastase
D
all of these
53
Which of the following statements about enzymes or their function is true?
A
Enzymes do not alter the overall change in free energy for a reaction
B
Enzymes are proteins whose three-dimensional form is key to their function
C
Enzymes speed up reactions by lowering activation energy
D
All of the above
54
Tryprotophan synthetase of E.coli, a typical bifunctional oligomeric enzyme consist of
A
a protein designated A
B
two proteins designated A and B
C
a protein A and one-subunit a
D
a protein designated B
55
What is the specificity of the Clostripain protease?
A
It cleave after Arg residues
B
It cleave after His residues
C
It cleave after Lys residues
D
None of the above
56
The proteolysis rate enhancement by chymotrypsin (~1010 folds) corresponds to a reduction in activation energy of about
A
40 kJ/mol
B
49 kJ/mol
C
58 kJ/mol
D
88 kJ/mol
57
Which of the following is false statement with regard to comparison between Serine and HIV proteases?
A
Both use nucleophilic attack to hydrolyze the peptide bond
B
Both require water to complete the catalytic cycle
C
Both forms an acyl-enzyme intermediate
D
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
A, B, C, and D will all still be produced
B
A, B, and C will still be produced, but not D
C
A and B will still be produced, but not C or D
D
A will still be produced, but not B, C, or D
59
The nucleophile in serine proteases is
A
Serine
B
water
C
both (a) and (b)
D
Asparagine
60
The role of Asp 102 and His 57 during trypsin catalysis is to
A
neutralize the charge on the other's side chain
B
keep the specificity pocket open
C
function as a proton shuttle
D
clamp the substrate into the active site
61
The cleavage specificity of trypsin and chymotrypsin depend in part on the
A
proximity of Ser 195 to the active site or specificity pocket
B
size, shape, and charge of the active site or specificity pocket
C
presence of a low-barrier hydrogen bond in the active site or specificity pocket
D
absence of water in the active site
62
The E.coli pyruvic acid dehydrogenase complex is reported to
A
decatalyze the oxidation of pyruvic acid to acetyl Co A and CO2
B
Catalyze the oxidation of pyruvic acid to acetyl Co A and CO2
C
retard the reduction of pyruvic acid to acetyl Co A and CO2
D
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?
A
Both require water to complete the catalytic cycle
B
Both use a base to activate the nucleophile
C
Both show specificity for certain amino acid sequences
D
All of the above
64
Before they can react, many molecules need to be destabilized. This state is typically achieved through
A
changing the three-dimensional shape of the molecule
B
oxidizing the molecules by removing electrons
C
changing the reaction from a biosynthetic to a catabolic pathway
D
the input of a small amount of activation energy
65
Common feature in all serine proteases is a
A
hydrophobic specificity pocket
B
hydrophilic specificity pocket
C
cluster of reactive serine residues
D
single reactive serine residue
66
How is the enzyme COX-1 important in human health?
A
It helps to transport carbon dioxide in the blood
B
It is critical for the biosynthesis of DNA
C
It is a chemical derivative of aspirin
D
It catalyzes the production of hormones that maintain the stomach lining
67
For specific antigen recognition by T cells,
A
antigen is bound by a T cell membrane antibody
B
denaturation of antigen does not reduce epitope recognition
C
MHC molecules are not required
D
antigen exposure during T cell maturation is required
68
Antigen, when injected in the body activates its specific lymphocytes in the
A
blood circulation
B
draining lymph nodes
C
MALT (mucosa associated
D
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)
A
adjuvant
B
carrier
C
hapten
D
mitogen
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