Two amino acids of the standard 20 contain hydroxyl-groups. They are: - answer✔threonine
and serine
There are several amino acid side chains which are always charged at physiological pH. These
are: - answer✔Glu, Asp, Lys, and Arg
Which one of the following sequences of five amino acids would most likely be located in the
interior of a globular soluble protein? - answer✔Met-Phe-Pro-Ile-Leu
What is the net charge at pH 7.0 on a peptide with the sequence?
Ala-Thr-Leu-Asp-Ala-Lys-Pro-Glu - answer✔-1
What would be the net charge for the peptide below at pH 7.0?
Asn-Asp-Cys-Tyr-Ser-Val-Lys - answer✔0
How many hydrophobic amino acid residues are present in the peptide shown? - answer✔2
The peptide shown has the amino acid sequence: - answer✔Val-Ser-Ile-Glu-Lys
Which statement is FALSE about the classification of amino acids? - answer✔Glutamic acid and
asparagine are negatively charged amino acids.
One of the amino acids that is classified as having a polar side chain is typically found buried in
the hydrophobic core of soluble globular proteins. Which of the following amino acids is it? -
answer✔Cys
Which statement(s) is/are TRUE about the following peptide? Ala-Cys-Gly-Met-Lys - answer✔It
has four peptide bonds
Using the table shown, identify which proteins would bind to an anion exchange column
equilibrated at pH 7.0. - answer✔2 & 4
Which of the following sequences of amino acids is most likely to be on the surface of a water-
soluble globular protein? - answer✔Glu-Asp-Lys
Which amino acid can be modified to make the following synthetic compound? - answer✔lysine
The following compound is a non-protein water soluble amino acid that is found in green tea.
Which amino acid is the precursor for this compound? - answer✔glutamic acid
How many charges the following peptide has at pH=7.0? - answer✔-1
ALL RIGHTS RESERVED.
A column containing carboxymethyl groups can be used to separate serum albumin and
ribonuclease A. Serum albumin has a pI of 4.9 and Ribonuclease A has a pI of 9.4. Which one of
these 2 proteins will bind to the column if both proteins are dissolved in a buffer solution with
pH=7.0? - answer✔ribonuclease A
Protein X has an absorptivity of 0.4 mL·mg-1·cm-1 at 280 nm. What is the absorbance at 280
nm of a 2.0 mg ·mL-1 solution of protein X? (Assume the light path is 1cm). - answer✔0.8
Consider a protein with the subunit composition indicated by the following
information:Molecular mass by gel filtration: 200 kDMolecular mass by SDS-PAGE: 100
kDMolecular mass by SDS-PAGE with 2-mercaptoethanol: 40 kD and 60 kD
What can be concluded from all of this data about the subunit composition of this protein? -
answer✔Two 40 kDa and two 60 kDa subunits
Which of the following forces stabilize protein primary structure at physiological pH? -
answer✔covalent bonds
Which of the following statements is true regarding sodium dodecylsulphate polyacrylamide gel
electrophoresis (SDS-PAGE)? - answer✔SDS-PAGE separates proteins on the basis of their
intrinsic charge and isoelectric point.
None of the statements is true.
SDS-PAGE separates nucleic acids on the basis of their charge.
Smaller proteins move through the gel faster under the influence of the electric field in SDS-
PAGE.
ANSWER: Smaller proteins move through the gel faster under the influence of the electric field
in SDS-PAGE.
Using the table shown, identify which proteins would elute together in a gel filtration
experiment. - answer✔1 & 2 and 4 & 5
Using the table shown, identify which proteins would migrate together during SDS-PAGE in the
absence of 2-mercaptoethanol. - answer✔2 & 3 and 4 & 5
Using the table shown, identify which proteins would give more than one product after a single
cycle of Edman degradation. - answer✔4 & 5
Which of the following is an example of a conservative amino acid substitution in a protein
structure? - answer✔Ser to Thr
ALL RIGHTS RESERVED.
Which of the following is NOT a conservative amino acid substitution in a protein structure? -
answer✔Arg to Phe
Which of the following amino acids is MOST likely to be a conservative substitution for glycine?
- answer✔ANSWER: Ala
Lue
Pro
Thr
Which reagent reduces disulfide bonds to sulfhydryl groups? - answer✔2-mercaptoethanol and
DTT (dithiothreitol)
Identify the least conservative amino acid substitution, assuming that these two residues occur
at the same position in two homologous proteins. - answer✔Glu --> Lys
Which of the following statements is not true about the Bradford assay? - answer✔It involves
the absorbance of light in the UV region by phenylalanine, tryptophan, and tyrosine.
Which of the following statements is not true about SDS-PAGE: - answer✔Proteins are
separated based on their size, shape and electric charge at a given pH.
Which of the following statements about affinity chromatography is not true: - answer✔In
metal chelate affinity chromatography, the matrix contains metal ions ligands (like Zn2+ or
Ni2+) so that proteins bearing metal-chelating groups (e.g., multiple His side chains) can be
retained.
The stronger the interaction between the ligand and the protein, the better the result of the
affinity purification.
The bound protein can be eluted by washing the column with a solution containing a high
concentration of free ligand or a solution of different pH or ionic strength.
ANSWER: It is a very effective means of separation because one can "fish out" the target
protein from a mixture of several proteins by exploiting its unique biochemical affinity for the
ligand.
A molecule (a ligand) that specifically binds to the protein of interest (e.g., a non-reactive
analog of an enzyme's substrate) is covalently attached to an inert matrix.
Which chemical reagent promotes peptide bond cleavage on the C-side (carboxyl side) of lysine
and arginine residues if the next residue is not proline? - answer✔trypsin
4|Page
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