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BCH403 Final Exam Questions And Answers

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BCH403 Final Exam Questions And Answers E1: A biochemical reaction, without a catalyst or thermodynamic coupling, takes 50 years to reach a state of equilibrium. Without more information, we cannot make a determination on either the value of Keq constant or the positive or negative value of the deltaG of the reaction. - Answer-FALSE /.E1: A chromatography column was used to try to purify a protein that is 10 kilodaltons in size. Some of the illusion fractions were run on SDS page and are shown below, with the lower numbered fractions eluting first period based only on this information, what kind of chromatographic column was used it was the attempt successful? The charges on the gel are shown on the left. [May insert picture later] - Answer-Nickel affinity, and it did work /.E1: A glycine residue is disruptive to the stability of an a-helix or a b-strand because: - Answer-It's R-group is too small to participate in stabilizing interactions with neighboring R - groups /.E1: A mutation in myoglobin that changes the distal histidine to an alanine will result in a lower P50 - Answer-FALSE /.E1: A single residue mutation to an enzyme decreases its rate constant by one half. This means the reaction now occurs more slowly. - Answer-TRUE /.E1: Ascorbate (Vitamin C) is an important part of any diet because: - Answer-It is utilized by the enzyme lysyl oxidase, which crosslinks lysine residues to stabilize the structure of tropocollagen. /.E1: Due to its small size, the amino acid glycine can be found in tight turns in a protein structure - Answer-TRUE /.E1: In an enzyme catalyzed reaction, the Delta Delta G naught ++ ( change in the free energy of activation) is found to be very small when compared to the net free energy of activation. Which of the following are also true of this reaction? - Answer-The velocity will increase slightly. /.E1: Most nonpolar 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 nonpolar 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 interactions? - Answer-Leucine -- Glutamine /.E1: One reason that we require myoglobin and hemoglobin to store and transport oxygen is because oxygen by itself has very poor solubility in water - Answer-TRUE /.E1: One strength of nuclear magnetic resonance spectroscopy is that it can detect multiple conformations of proteins and one of its limitations is that proteins must contain certain isotopes. - Answer-TRUE /.E1: 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. - Answer-FALSE /.E1: The deltaG of a reaction is defined as the energy required to bring the concentration of the reactants and products to equal concentration. - Answer-FALSE /.E1: The following oxygen binding curves are derived from independent experiments. which of the following statements is not true regarding these plots? [Plot picture may insert later] - Answer-when comparing 3 with 4 comma careforce less likely to be bound to BPG /.E1: the following peptide is composed of which amino acid sequence [Picture of sequence. May insert later] - Answer-LKQIFKDIWTIGW /.E1: 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 true regarding the structure of this Alpha Helix? QFLRDTANSLLDNLIT - Answer-Mutation from the phenylalanine residue to a proline will prevent the rest of the sequence from forming an Alpha Helix. /.E1: The peptide in question 17 is dissolved into a solution that has a pH of 6.5. Under these conditions the net charge of the peptide is - Answer-+1 /.E1: The residue sequence of a fibrous protein is shown below. which protein does this sequence likely correspond to? MGISQKLYRDVNNAFQSRINYWLS - Answer-fibroin /.E1: The stabililty of an a-helix is partly due to the hydrogen bonding that occurs between the carbonyl oxygen of one helix and the amide hydrogen of a neighboring a-helix - Answer-FALSE /.E1: The structural changes in hemoglobin that contribute toward its positive cooperativity for oxygen consist of: - Answer-All of the above ( movement of iron into the plane of the heme & movement of a neighboring veiling residue due to strain from changes in the heme & the breaking of a covalent bond with the regulatory molecule BPG /.E1: What is the molecular basis for sickle cell anemia? - Answer-A polar surface residue in hemoglobin is mutated to valine, a nonpolar residue, causing the protein to aggregate into fibers /.E1: Which of the following is true regarding Michaelis-Menton enzyme kinetics? - Answer-B and C are correct (the Michaelis constant (KM) is the substrate concentration when the velocity is one half of maximum & at infinite substrate concentration, the reaction becomes zero order with respect to substrate) /.E1: Which of the following is true regarding oxygen binding to one molecule of myoglobin? - Answer-B and C (A histidine is required to hydrogen bond with the bound oxygen thus stabilizing it. & the iron atom is located outside the plane of the heme when oxygen is not bound) /.E1: Which of the following statements is true regarding the hydrophobic effect? - Answer-Non - Polar molecules are driven together in order to maximize the entropy of water. /.E1: Which of the following tripeptides will bind to an anion exchange column at pH 7 Peptide A: Glu-Lys-Arg Peptide B: Glu-Asp-Arg - Answer-Peptide B will bond /.E1: Why do proteins fold? - Answer-A and B are correct (It is entropically favorable for water & It is enthalpically favorable for the protein) /.E1: 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 - HCO3- + H30+ If a solution of 0.5M carbonic acid is adjusted to a pH of 2.5, the primary form of the buffer will be: - Answer-H2CO3 /.E1: 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? - Answer-B and D ( it's hemoglobin will have a very low P50 value & the primary amino acid sequence of its hemoglobin will not be identical to that of a species living in an oxygen rich atmosphere) /.E1: Your goal is to separate a mixture of the two polypeptides shown below, and obtain purified peptide one for further study as a neurotransmitter. which purification technique would be most effective and why?

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E1: A biochemical reaction, without a catalyst or thermodynamic coupling, takes 50
years to reach a state of equilibrium. Without more information, we cannot make a
determination on either the value of Keq constant or the positive or negative value of the
deltaG of the reaction. - Answer-FALSE

/.E1: A chromatography column was used to try to purify a protein that is 10 kilodaltons
in size. Some of the illusion fractions were run on SDS page and are shown below, with
the lower numbered fractions eluting first period based only on this information, what
kind of chromatographic column was used it was the attempt successful? The charges
on the gel are shown on the left.

[May insert picture later] - Answer-Nickel affinity, and it did work

/.E1: A glycine residue is disruptive to the stability of an a-helix or a b-strand because: -
Answer-It's R-group is too small to participate in stabilizing interactions with neighboring
R - groups

/.E1: A mutation in myoglobin that changes the distal histidine to an alanine will result in
a lower P50 - Answer-FALSE

/.E1: A single residue mutation to an enzyme decreases its rate constant by one half.
This means the reaction now occurs more slowly. - Answer-TRUE

/.E1: Ascorbate (Vitamin C) is an important part of any diet because: - Answer-It is
utilized by the enzyme lysyl oxidase, which crosslinks lysine residues to stabilize the
structure of tropocollagen.

/.E1: Due to its small size, the amino acid glycine can be found in tight turns in a protein
structure - Answer-TRUE

/.E1: In an enzyme catalyzed reaction, the Delta Delta G naught ++ ( change in the free
energy of activation) is found to be very small when compared to the net free energy of
activation. Which of the following are also true of this reaction? - Answer-The velocity
will increase slightly.

/.E1: Most nonpolar 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 nonpolar 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 interactions? - Answer-Leucine --> Glutamine

, /.E1: One reason that we require myoglobin and hemoglobin to store and transport
oxygen is because oxygen by itself has very poor solubility in water - Answer-TRUE

/.E1: One strength of nuclear magnetic resonance spectroscopy is that it can detect
multiple conformations of proteins and one of its limitations is that proteins must contain
certain isotopes. - Answer-TRUE

/.E1: 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. - Answer-FALSE

/.E1: The deltaG of a reaction is defined as the energy required to bring the
concentration of the reactants and products to equal concentration. - Answer-FALSE

/.E1: The following oxygen binding curves are derived from independent experiments.
which of the following statements is not true regarding these plots?

[Plot picture may insert later] - Answer-when comparing 3 with 4 comma careforce less
likely to be bound to BPG

/.E1: the following peptide is composed of which amino acid sequence

[Picture of sequence. May insert later] - Answer-LKQIFKDIWTIGW

/.E1: 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 true
regarding the structure of this Alpha Helix?

QFLRDTANSLLDNLIT - Answer-Mutation from the phenylalanine residue to a proline
will prevent the rest of the sequence from forming an Alpha Helix.

/.E1: The peptide in question 17 is dissolved into a solution that has a pH of 6.5. Under
these conditions the net charge of the peptide is - Answer-+1

/.E1: The residue sequence of a fibrous protein is shown below. which protein does this
sequence likely correspond to?

MGISQKLYRDVNNAFQSRINYWLS - Answer-fibroin

/.E1: The stabililty of an a-helix is partly due to the hydrogen bonding that occurs
between the carbonyl oxygen of one helix and the amide hydrogen of a neighboring a-
helix - Answer-FALSE

/.E1: The structural changes in hemoglobin that contribute toward its positive
cooperativity for oxygen consist of: - Answer-All of the above ( movement of iron into the

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