Proteins can denature due to a change in
A) pH.
B) temperature.
C) ionic strength.
D) all of the above
E) none of the above
Examine the three sequences below for collagen-like proteins. If hydrogen bonding were
the most important feature in determining strength in fibrous proteins, which of the following
sequences likely has the highest melting temperature and why? (Note: Flp = fluoroproline; Hyp
= hydroxyproline)
I. Pro-Hyp-Gly-Pro-Hyp-Gly-Pro-Hyp-Gly
II. Pro-Flp-Gly-Pro-Flp-Gly-Pro-Flp-Gly
III. Gly-Pro-Thr-Gly-Pro-Thr-Gly-Pro-Thr
A) "1" because Hyp has OH groups
B) "1" because the electronegativity of oxygen is greater
C) "2" because the electronegativity of proline is greater
D) "2" because the electronegativity of the -OH group increases hydrogen bond strength
E) "3" because Thr is a small amino acid which allows close packing
Based on what you know about fibrous protein structure and sequence, what type of fibrous
protein is this sequence most likely to from (You can assume that the protein is longer than what
is shown and is repeating as shown, also note the polarity of each amino acid.)?
Val - Cys - Lys - Val - Cys - Ala - Cys - Val - Cys - Lys - Val - Cys - Ala - Cys
A) alpha keratin
B) β keratin
C) collagen
D) pleated collagen
E) This sequence cannot be from any of the structural proteins.
Which of the following structural proteins has the greatest elasticity?
A) a keratin
B) β ketatin
C) collagen
D) pleated collagen
E) A and B are equal
Noncovalent interactions account for the strength of which of the following structural proteins?
A) a keratin
B) collagen
C) pleated collagen
D) A and B
E) B and C
Examine the three sequences below for collagen-like proteins and their melting temperatures (Tm). (Note: Flp = fluoroproline; Hyp = hydroxyproline) Based on this data, what is the most
important feature in determining the strength of the collagen protein?
A) hydrogen bonding
B) inductive effect
C) electrostatic effect
D) electrostatic and Inductive effect are equal
E) hydrogen bonding and inductive effect are equal
When considering fibrous proteins, which of the following statements is TRUE?
A) Noncovalent interactions contribute to the strength of all of these proteins.
B) All of them consist of alpha helix structure.
C) All of them require vitamin C.
D) Decrease in amounts of any of them cause scurvy.
E) All of these are true of fibrous proteins.
In a Ramachandran diagram the region representing the angles of and that correspond to those commonly made by an amino acid that favors a left-handed helix are different from those angles commonly made by an amino acid that favors right-handed helix formation. Which of the following statements provides a plausible explanation for this difference?
A) Groups which would normally undergo high steric hindrance in the right-handed arrangement are separated maximally in the left-handed arrangement.
B) Left-handed helices have smaller pitch than right-handed helices.
C) The peptide backbone can coil tighter in the left-handed helices than in the right-handed
helices.
D) Left-handed helices exhibit cyclic symmetry, while righthanded helices are asymmetric.
E) All of the above are plausible explanations.
Molecular chaperones bind to unfolded or partially folded polypeptide chains in order to
accomplish which of the following?
A) ensure that improper aggregation of hydrophobic segments does not occur
B) engulf the protein in order to ensure that the protein is not damaged by heat denaturation
C) facilitate native folding by exposing hydrophobic segments of the protein as it is
synthesized
D) facilitate aggregation of multiple subunits of a protein during synthesis
E) All of the above are accomplished by molecular chaperones.
