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BCH 403 Final Exam questions with complete solutions
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BCH 403 Final Exam questions with complete solutions
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BCH 403 Final ExamT or F: A biochemical reaction, without a catalyst or thermodynamic coupling, takes 50 years to reach a
state of equilibrium. W/o more information, we cannot make a determination on either the value of the
Keq constant or the positive or negative value of the DeltaG of the reaction - correct answer ✔✔False
T or F: Due to its small size, the amino acid glycine can be found in tight turns in a protein structure -
correct answer ✔✔True
T or F: The Delta G of a reaction is defined as the energy required to bring the concentration of reactants
and products to equal concentration - correct answer ✔✔False
T or F: One strength of NMR is that it can detect multiple conformations of proteins and one of its
limitations is that proteins must contain certain isotopes - correct answer ✔✔True
T or F: A single residue mutation to an enzyme decreases its rate constant by one half. This means the
reaction now occurs more slowly. - correct answer ✔✔True
T or F: The hydrophobic packing of non-polar residues is thermodynamically favorable b/c of both the
hydrophobic effect and a larger number of weak van der waals - correct answer ✔✔True
T or F: The classic experiment in which the protein ribonuclease A is first denatured and reduced, then
refolded, was used to demonstrate the role of aromatic residues in stabilizing covalent disulfide bonds -
correct answer ✔✔False
T or F: One reason that we require myoglobin and hemoglobin to store and transport oxygen is b/c
oxygen itself has very poor solubility in water - correct answer ✔✔True
T or F: A mutation in myoglobin that changes the distal histidine into alanine will result in a lower P50 -
correct answer ✔✔False
,The stability of an alpha helix is partly due to hydrogen bonding that occurs between carbonyl oxygen of
one helix and the amino hydrogen of a neighboring alpha helix - correct answer ✔✔False
Which of the following statements if true regarding the hydrophobic effect - correct answer ✔✔Non-
polar molecules are driven together in order to maximize the entropy of water
The peptide in question 17 is dissolved into a soln that has a pH of 6.5. Under these conditions, the net
charge of the peptide is - correct answer ✔✔+1
A glycine residue is disruptive to the stability of an alpha helix or a beta strand because - correct answer
✔✔It's R group is too small to participate in stabilizing interactions with neighboring R groups
With a pKA of 6.37, the carbonic acid/bicarbonate system serves to buffer changes to the pH of blood.
The acid dissociates as follows
H2CO3 + H20 ----> (DOUBLEARROW) HCO3- + H3O+
If a solution of .5 M carbonic acid is adjusted to a pH of 2.5, the primary form of the buffer will be: -
correct answer ✔✔H2CO3
Most non-polar residues are located on the interior of a protein fold, but are occasionally found on
surfaces where they can mediate protein interactions. The molecular basis of a hypothetical infectious
disease is that a bacterial protein interacts with a human protein by sharing a non-polar surface. Your
goal as a researcher is to find a way to disrupt this interaction. Which of the following surface mutations
are most likely to disrupt the protein interaction? - correct answer ✔✔leucine-->glutamine
You've discovered a new species of rodent living at a very high altitude, where the partial pressure of
oxygen is low. What would you predict regarding the oxygen-binding capacity of this new species? -
correct answer ✔✔It's hemoglobin will have a very low P50 value AND The primary amino acid sequence
of its hemoglobin will not be identical to that of a species living in an oxygen-rich atmosphere
The following peptide is composed of which amino acid sequence - correct answer ✔✔LKQIFKDIWTIGW
, The following sequence of 16 residues represents an alpha helical stretch in an enzyme from the
bacterium that causes tuberculosis. Which of the following is NOT TURE regarding the structure of this
alpha helix
QFLRDTANSLLDNLIT - correct answer ✔✔Mutation of they phenylalanine residue to a proline will
prevent the rest of the sequence from forming an alpha helix
The residue sequence of a fibrous protein is show below. Which protein does it most likely correspond
to?
MGISQKLYRDVNNAFQSRINYWLS - correct answer ✔✔Fibroin
Which of the following is true regarding oxygen binding to one molecule of myoglobin - correct answer
✔✔A histidine is required to hydrogen-bond with the bound oxygen, thus stabilizing it AND the iron
atom is located outside the plane of the heme when oxygen is not bound
A chromatography column was used to try to purify a protein that is 10 kDa in size. Some of the elution
fractions were run on SDS-PAGE and are shown blow ,with lower numbered fractions eluting first. Based
on this information, what kind of chromatographic column was used and was this attempt successful?
The charges on the gel are shown on the left - correct answer ✔✔Gel filtration, and it did work
Your goal is to separate a mixture of the two polypeptides shown below, and obtain a purified peptide 1
for further study as a neurotransmitter. Which purification technique would be most effective and why?
Peptide 1: MHTRRAPLQAWKKPRADHVL
Peptide 2:
MHTDEAPLQAWKDPEADHVLW - correct answer ✔✔Cation exchange, since peptide 1 is more positively
charged and will "stick" to that resin best
Ascorbate (Vitamin C) is an important part of any diet because - correct answer ✔✔It is required by
enzymes that hydroxylate lysine and proline, which allows these side chains to participate in stabilizing
hydrogen bonds b/t strands of tropocollagen
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