Protein Stability(Biochemistry ) Questions and Answers

Question 1. At the midpoint of a temperature transition curve,
  1.    All of these
  2.    half of the protein is denatured
  3.    Keq = 1.0 and ΔG = 0
  4.    [Native] = [Unfolded]
Explanation:-
Answer: Option A. -> All of these
Question 2. Unpaired H-bond donors and acceptors are found in the hydrophobic core of a protein
  1.    only at the turns connecting p-strands
  2.    only on Pro residues
  3.    rarely
  4.    only at the ends of a-helices
Explanation:-
Answer: Option C. -> rarely
Question 3. For the unfolding reaction of Protein G, ΔH° =210.6 kJ/mol, this means that
  1.    the entropy is positive at all temperatures
  2.    folding is favored enthalpically
  3.    unfolding is favored enthalpically
  4.    the entropy is negative at all temperatures
Explanation:-
Answer: Option B. -> folding is favored enthalpically
Question 4. Which of the following forces is the most favorable for protein folding?
  1.    Vander Waals interactions
  2.    Hydrophobic Interactions
  3.    Conformational entropy
  4.    Hydrogen bonds
Explanation:-
Answer: Option B. -> Hydrophobic Interactions
Question 5. Attractive Vander Waals forces occur between
  1.    only if other forces are less favorable
  2.    polar molecules in the solid state
  3.    any pair of nearby atoms
  4.    apolar molecules in the liquid state
Explanation:-
Answer: Option C. -> any pair of nearby atoms
Question 6. Since ΔG° = -RTlnK
  1.    a 10-fold decrease in K increases ΔG° by about 10-fold
  2.    a 10-fold increase in K decreases ΔG° by about 10-fold
  3.    a 10-fold decrease in K decreases ΔG° by about 2.3*RT
  4.    a 10-fold increase in K decreases ΔG° by about 2.3*RT
Explanation:-
Answer: Option D. -> a 10-fold increase in K decreases ΔG° by about 2.3*RT
Question 7. Which of the following is the most correct?
  1.    Charged amino acids are seldom buried in the interior of a protein
  2.    Tyrosine is only found in the interior of proteins
  3.    All hydrophobic amino acids are buried when a protein folds
  4.    Charged amino acids are never buried in the interior of a protein
Explanation:-
Answer: Option A. -> Charged amino acids are seldom buried in the interior of a protein
Question 8. If the egg white protein, ovalbumin, is denatured in a hard-boiled egg, then which of the following is least affected?
  1.    The secondary structure of ovalbumin
  2.    The quaternary structure of ovalbumin
  3.    The tertiary structure of ovalbumin
  4.    The primary structure of ovalbumin
Explanation:-
Answer: Option D. -> The primary structure of ovalbumin
Question 9. Which of the following forces is the most unfavorable for protein folding?
  1.    Hydrophobic interactions
  2.    Conformational entropy
  3.    Vander Waals interactions
  4.    Electrostatic interactions
Explanation:-
Answer: Option B. -> Conformational entropy
Question 10. The correlation between free energy ΔG transfer between the aqueous/organic phases and the surface area of amino acid residues
  1.    is similar to effects seen with SDS denaturation
  2.    reflects the reduction in solvent-accessible area during protein folding
  3.    is only meaningful for the polar amino acids
  4.    ignores the important contribution of the peptide bond
Explanation:-
Answer: Option B. -> reflects the reduction in solvent-accessible area during protein folding
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