BIO 361 Lecture Notes - Lecture 1: Oligomer, Nuclear Magnetic Resonance, Lactone
29 Jun 2018
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1) A decrease in disorder in the system during a thermodynamic process:
a) prevents a process from being spontaneous.
b) results in an increase in entropy.
c) is characteristic of a system increasing in enthalpy.
d) results in the term TdeltaS being negative
e) is found in every exergonic process.
2) You monitor the progress of a thermodynamic process and observe that the process occurs
spontaneously at all temperatures but at a very slow kinetic rate. Which of the following
statements about this process can be said with complete confidence?
a) The process has only a slightly negative ΔG value.
b) The process has a negative ΔH and a negative ΔS value.
c) The process has a positive ΔH and a positive ΔS value.
d) The process has a negative ΔH and a positive ΔS value.
e) The process has only a slightly positive ΔG value.
3) Which of the following is the best explanation for the hydrophobic effect?
a) It is caused by an affinity of hydrophobic groups for each other.
b) It is caused by the affinity of water for hydrophobic groups.
c) It is an entropic effect, caused by the tendency of water molecules to maximize their
entropy by forming highly ordered structures around the hydrophobic groups.
d) It is an enthalpic effect, caused by the formation of bonds between hydrophobic groups in
an aqueous solution.
e) It is an entropic effect caused by the desire of hydrophobic groups to increase their
entropy by associating with other hydrophobic groups.
4) Which of the following statements about the response of an aqueous solution of acid to the
addition of base is TRUE?
a) The addition of base to a solution of weak acid will cause a change in the pK value of the
acid.
b) The addition of a fixed volume of base to a solution of weak acid will change the pH of
the solution by an equal amount each time.
c) A strong acid will act as a more effective buffer to maintain a constant pH than a weak
acid at physiological pH values.
d) A weak acid will reach its maximal buffering capacity when [HA]=[A-].
e) A weak acid that contains multiple ionizable groups will display a single titration point
equal to the average of the pK values of each group.
5) You conduct an SDS-PAGE experiment on a mixture of three tripeptides with the sequences:
Arg-Trp-Trp, Ala-Ala-Ala, and Asp-Phe-Phe. Which of the following statements about the
results of the experiment are correct?
a) Arg-Trp-Trp will migrate the furthest because of the overall positive charge on the
peptide.
b) Asp-Phe-Phe will migrate the furthest because of the overall negative charge on the
peptide.
c) Arg-Trp-Trp will migrate the furthest because it has the highest molecular weight.
d) Ala-Ala-Ala will migrate the furthest because it has the lowest molecular weight.
e) Ala-Ala-Ala will migrate the furthest because it has the most neutral pI value.
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Page 2 of 6
6) Proteins sometimes contain amino acid residues that do not belong to the 20 standard amino
acids. These modified amino acids:
a) Are synthesized due to genetic mutations.
b) Are modified and then incorporated into the protein on the ribosome.
c) Are formed by modification of the side chains of standard amino acid residues after the
protein is synthesized.
d) Are toxic.
e) Are racemic.
7) You wish to separate a mixture of glutamic acid, lysine, and arginine amino acids by ion
exchange chromatography. Which of the following conditions would be most appropriate to
allow the glutamic acid to elute with the LONGEST retention time.
a) Add the mixture to a cation exchange column at pH 7.
b) Add the mixture to a cation exchange column at pH 3.
c) Add the mixture to an anion exchange column at pH 3.
d) Add the mixture to an uncharged stationary phase column at pH 7.
e) Add the mixture to an anion exchange column at pH 7.
8) A protein elutes from a gel filtration column with a retention time corresponding to a molecular
weight between 420 kDa and 460 kDa. The protein then migrates as a single band between
200 kDa and 240 kDa in an SDS-PAGE experiment in the absence of mercaptoethanol, and
as a single band between 100 kDa and 120 kDa after SDS-PAGE in the presence of
mercaptoethanol. Which of the following statements is most consistent with the information
provided?
a) The protein is composed of four subunits, each with a molecular weight of ~110kDa and
each containing at least one residue with a sulfur atom in its side chain.
b) The protein is composed of a single subunit with a molecular weight of ~220kDa and
contains at least two residues with charged side chains.
c) The protein is composed of two subunits that form an oligomer with a total molecular
weight of ~440kDa.
d) The protein contains covalent bonds that only link the side chains of two residues within
the same polypeptide chain.
e) The protein is composed of four subunits with different primary structures.
9) You are attempting to sequence a five-residue peptide. Which statement is most consistent
with the results obtained?
a) If you reacted the peptide with dansyl chloride followed by incubation with elastase to
generate two peptide fragments you would expect that the original peptide contained a
bulky hydrophobic residue.
b) If you reacted the peptide with dansyl chloride followed by boiling in aqueous acid you
could identify the N-terminal amino acid by following an intense blue fluorescence after
chromatography.
c) If you treated the peptide with chymotrypsin and failed to observe any cleavage, you
would suspect that the peptide has no lysine or arginine residues in the sequence.
d) If you reacted the peptide with dansyl chloride followed by cyanogen bromide to generate
a dansylated tripeptide with a C-terminal homoserine lactone, you would suspect that the
third amino acid residue from the N-terminus is methionine.
e) If addition of PITC to the peptide failed to yield any reaction you would suspect that the
C-terminus of the peptide does not contain an accessible carboxylate group.
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Document Summary
It is caused by an affinity of hydrophobic groups for each other. It is caused by the affinity of water for hydrophobic groups. It is an entropic effect, caused by the tendency of water molecules to maximize their entropy by forming highly ordered structures around the hydrophobic groups. It is an enthalpic effect, caused by the formation of bonds between hydrophobic groups in an aqueous solution. Page 1 of 6: proteins sometimes contain amino acid residues that do not belong to the 20 standard amino acids. The protein then migrates as a single band between. 200 kda and 240 kda in an sds-page experiment in the absence of mercaptoethanol, and as a single band between 100 kda and 120 kda after sds-page in the presence of mercaptoethanol. If you reacted the peptide with dansyl chloride followed by incubation with elastase to generate two peptide fragments you would expect that the original peptide contained a bulky hydrophobic residue.
