WorksheetsBCHS 3304 Exam 2
Total questions: 43
Worksheet time: 22mins
Local spatial alignment of amino acid backbone without regard to side chains is the _____ of proteins.
Primary structure
Secondary structure
Tertiary structure
Quaternary structure
None of the above
In right handed α-Helix, a hydrogen bond may be found between the C=O of the 5th residue and the N-H of the _____ residue.
7th
8th
9th
10th
11th
A β-turn takes a minimum of _____ residues
3
4
5
6
7
The torsion angle between Cα and N on an amide plane is called the _____ angle.
Δ
μ
Ф
ψ
ξ
The Ф and ψ angle combination for right-handed α-helix is most likely____
-57, -47
-119, 113
-139, 135
-49, -26
-51, 153
The Ф and ψ angle combination for antiparallel β sheet is most likely____
-57, -47
-119, 113
-139, 135
-49, -26
-51, 153
In a protein, the most conformationally restricted amino acid is ______; the least conformationally restricted is ______.
Trp, Gly
Met, Cys
Pro, Gly
Ile, Ala
Ala, Pro
Which of the following has (have) both a favorable hydrogen bonding pattern and Ф and ψ values that fall within the allowed Ramachandran conformational regions?
α helix
collagen helix
β sheet
all of the above
none of the above
Which one of these characteristics is not true for the α helix?
There are 3.6 amino acids per turn.
There is a requirement for glycine every third amino acid residue.
A hydrogen bond forms between the carbonyl oxygen of the n th amino acid residue and the -NH group of the (n + 4) th amino acid residue.
Proline is typically not found in the α helix.
It is right-handed.
Myosin and a-keratin have coiled coil structure, and the amino acid sequences of them often show 7-residue pseudo repeats. In the following section of the coiled coil structure, residues a, d, a’, d’ are often _____
hydrophobic
hydrophilic
positively charged
negatively charged
Gelatin is mostly collagen. Which of the following amino acid or amino acid derivative is least abundant in gelatin?
Gly
Hyp
Pro
Ala
Cannot determine
In the absence of ascorbic acid, prolyl oxidase is unable to oxidize proline residues in collagen to hydroxyproline, resulting in:
lathyrism
prion diseases
amyloid formation
scurvy
allysine
Calculate the length in angstroms of a 50-residue segment of the a keratin coiled coil (a keratin has a pitch of 5.1 angstroms, and n=3.5 residues/turn)
73
30
32
34
36
X-ray Crystallography primarily measures ______.
Resonance frequencies
Torsion angles
Peptide bond strength
Electron density
None of the above
Proteins can denature due to a change in
pH.
temperature.
ionic strength.
all of the above
none of the above
The salting in of proteins can be explained by:
salt counter-ions reducing electrostatic attractions between protein molecules.
salt ions reducing the polarity of the solution.
salt ions increasing the hydrophobic interactions.
releasing hydrophobic proteins from nonpolar tissue environments.
hydration of the salt ions reducing solubility of proteins.
(NH4)2SO4 is the salt of choice for “salt out” protein purification, because_____
It has no net charge at pI
It forms covalent bonds with most proteins
it is highly soluble
None of the above
His-tag is widely used in cloned protein purification. It is one type of ______
Ion exchange chromatography
Gel filtration
Reverse-phase chromatography
Affinity chromatography
Hydrophilic chromatography
Which of the following polypeptides is predicted to have the highest absorbance at 280 nm?
Trp-Tyr-Phe
Trp-Ala-His
Leu-Tyr-Glu
Asp-Arg-Phe
Trp-Ala-Trp
Ammonium sulfate is used to purify protein W (pI=5.5) by sorting out from a solution at pH6.8. How should pH be adjusted to maximize protein precipitates?
Use a HCl solution to bring down pH to 5.5
Use a NaOH solution to raise pH to 7.4, the physiological pH in plasma.
pH should not be adjusted.
pH should be adjusted to other points not listed above.
In what order would Glu, Lys and Val be eluted from a diethylaminoethyl column (Hint: this is an ion exchange chromatography column) at pH8?
Glu, Lys, Val
Lys, Glu, Val
Val, Glu, Lys
Lys, Val, Glu
Val, Lys, Glu
With the following information, what is the likely subunit composition of this protein? Molecular mass by gel filtration: 100 kD Molecular mass by SDS-PAGE: 50 kD Molecular mass by SDS-PAGE with 2-mercaptoethanol: 20 kD and 30 kD
The protein contains two 20 kD polypeptides and two 30 kD polypeptides. Each 20 kD chain is disulfate bonded to a 30 kD chain. Then the resulting 50 kD units associate noncovalently to form the 100 kD protein.
The protein contains 3 subunits, of molecular mass 50 kD, 20 kD, 30 kD, respectively. The total protein mass is 100 kD.
The protein contains two 20 kD polypeptides and two 30 kD polypeptides. Each 20 kD chain is noncovalently associated to a 30 kD chain. Then the resulting 50 kD units disulfate bond to form the 100 kD protein.
None of the above.
An enzyme-linked immunosorbent assay requires
a radioactive substrate.
a radioactive standard for binding to the antibody.
aromatic amino acids.
an antibody that binds the protein of interest.
a catalytic antibody.
Which physical characteristic is not commonly used in protein separation?
solubility
stereochemistry
size
charge
polarity
A technique that can be used to separate proteins based primarily on their pI is called
ion-exchange chromatography.
gel filtration chromatography.
affinity chromatography.
isoelectric focusing.
hydrophobic interaction chromatography.
You have a mixture of histidine and arginine, how would you try to separate these two amino acids?
anion exchange chromatography at pH 2
anion exchange chromatography at pH 4
cation exchange chromatography at pH 2
cation exchange chromatography at pH 4
cation exchange chromatography at pH 9
You are trying to separate five proteins, which are listed below, by gel filtration chromatography. Which of the proteins will elute last from the column?
cytochrome c (12 kDa)
RNA polymerase (99 kDa)
glutamine synthetase (621 kDa)
interferon-γ (34 kDa)
hemoglobin (62 kDa)
The following is a sample purification provided by the vendor. We can conclude that under the experiment condition here, _____
Fetal hemoglobin has the most charge
Hemoglobin has the most charge
Sickle cell hemoglobin has the most charge
Hemoglobin C has the most charge
SDS-PAGE separates proteins primarily due to differences in
isoelectric point.
mass.
polarity.
solubility.
amino acid sequence.
Myoglobin’s secondary structure is primarily composed of ______________.
parallel β-sheets
antiparallel β-sheets
α-helices
β-loops
polyproline helices
Within days, his blood ____ concentration increased, thus his hemoglobin can release more oxygen to tissues throughout the body.
CO2
myoglobin
O2
BPG
hemoglobin
Carbon monoxide binds to heme:
with a higher affinity than oxygen.
resulting in the oxidation of the Fe(II) to Fe(III)
in a manner that displaces carbon dioxide, causing CO2 poisoning.
from the side opposite oxygen, resulting in a brown colored heme.
with a lower affinity than oxygen.
When the partial pressure of O2 in venous blood is 30 torr, the saturation of myoglobin with O2 is ______ while the saturation of hemoglobin with O2 is ______.
0.55, 0.91
0.91, 0.55
2.8 torr, 26 torr
0.91, 0.97
none of the above
The value of n, the Hill constant (coefficient), for hemoglobin is about ______ as great as the value for myoglobin.
half
twice
three times
five times
ten times
The Bohr effect refers to
the decrease in affinity of Hb for O2 when the pH goes down
the decrease in affinity of Hb for O2 when the pH goes up
the increase in the affinity of Hb for O2 when the O2 concentration goes up
the decrease in affinity of Hb for O2 when the BPG concentration goes up
the decrease in affinity of Hb for O2 when the BPG concentration goes down
In sickle-cell anemia, the negatively charged glutamic acid residue is replaced by the neutral amino acid ____________.
tyrosine
lysine
valine
adenosine
glycine
About myoglobin and hemoglobin, which of the following is NOT true?
Myoglobin is a monomer while hemoglobin is a tetramer.
Myoglobin has higher affinity to O2 than hemoglobin.
Myoglobin-O2 binding is hyperbolic while hemoglobin-O2 binding is sigmoidal.
Myoglobin is mainly used in muscle respiration, while hemoglobin is for O2 transportation.
Myoglobin-O2 binding is a good example of ligand cooperative binding.
What protein has the following structure?
myosin
actin
antibody
hemoglobin
collagen
On SDS-PAGE in denaturing condition, purified myosin will show ____ bands.
1
2
3
4
5
Papain cleaves IgG to Fc and Fab fragments. Of these fragments, where is the antigen binding site located?
Constant regions of Fab
Variable regions of Fab
Fc
All fragments are required for antigen binding
Microfilament treadmilling refers to
myosin heads walking along actin microfilaments.
actin and myosin filaments sliding along each other.
actin monomers moving through a microfilament from the + end to the –end.
synthesis and degradation of actin monomers.
the interactions between actin and tropomyosin.
Based on the O2 binding curves of fetal and adult hemoglobin, which of the following statements is true?
Fetal hemoglobin has higher O2 affinity
Fetal hemoglobin has lower P50 than adult hemoglobin
Fetal hemoglobin releases less O2 to tissues than adult hemoglobin
All of the above
None of the above
Muscle contraction is directly caused by
structural changes in actin.
structural changes in myosin.
thick and thin filaments sliding past each other.
structural changes in the Z disk.
None of the above is correct.
