Biochem exam #2
Which of the following statements regarding peptide bonds is least accurate? -
ANSWER: Favored conformation of peptide bonds is with the sequential alpha carbons
in cis position.
Correct: Trans position
Which of the following amino acids is found most frequently at beta turns in the
secondary structures of proteins? - ANSWER: Proline
Which of the following secondary structures is most likely to be found in a membrane
embedded portion of a protein? - ANSWER: An alpha helix composed entirely of
hydrophobic residues
The amino acid that would be expected to be located within the interior of a folded
protein suspended in an aqueous buffer would be - ANSWER: Isoleucine because it's
non polar
The amino acid that would disrupt the ordered structure of a folded alpha helix would be
- ANSWER: Proline because of the compound formation
The amino acid that could be modified by addition of a phosphate group would be -
ANSWER: Tyrosine because of the aromatic ring
A histidine residue is in the active site of an enzyme and has a glutamate residue
nearby, What effect would the nearby glutamate have on the pea of the histidine? -
ANSWER: Glutamate is an acidic amino acid because it has a negative charge and
would favor a positively charged amino acid like Histidine.
Favoring a positively charged form makes histidine a weaker acid causing the pka to go
up.
Experiments on denaturation and renaturation after the reduction and deoxidation of the
disulfide bonds in the enzyme RNase have shown that: - ANSWER: the primary
sequence of RNase is sufficient to determine its specific secondary and tertiary
structure
The side chain of serine could interact with the side chain of ________ using a
________ - ANSWER: His, hydrogen bond
, For a globular protein that is found in the cytosol, ___ would most likely be found in the
proteins interior while ___ would most likely be found on the surface. - ANSWER: Leu,
Ser
Which of the following interactions would be involved in quaternary structure? -
ANSWER: Hydrogen bonds, hydrophobic interactions, disulfide bonds, and salt bridges
In a site directed mutagenesis experiment a specific Leu residue in a protein was
changed to various other residues. Predict which if the following changed would have
the greatest impact on the structure and function of the protein. - ANSWER: Asp
Which of the following is the driving force for protein folding? - ANSWER: Hydrophobic
effect
Molecular chaperones assist unfolded proteins by - ANSWER: Protecting the unfolded
protein from inappropriate protein protein interactions as the protein is synthesized .
Inducing rapid and precise folding of proteins into their correct conformations
Protein domains are - ANSWER: independently folded regions with a tertiary function,
often with a specific and unique function
Amino acids with R groups that have H-bond potential are - ANSWER: Serine,
Glutamate, Tyrosine and threonine (all have OH groups)
A Ramachandran plot shows: - ANSWER: shows the favored and disfavored phi and psi
angles.
pH < pKa - ANSWER: favors COOH and NH3+
pH > pKa - ANSWER: favors COO- and NH2
Hydrogen bond donor - ANSWER: N-H group (positive charge)
Hydrogen acceptor - ANSWER: C=O group (negative charge)
Phi angle (Φ): - ANSWER: angle of rotation about the single bond between the nitrogen
and the alpha carbon atom
Psi angle (Ψ): - ANSWER: angle of rotation about the single bond between the alpha
carbon and the carbonyl carbon atom
Petide bond is between - ANSWER: C=O and N-H
Primary structure - ANSWER: The first level of protein structure; the specific sequence
of amino acids making up a polypeptide chain.
Which of the following statements regarding peptide bonds is least accurate? -
ANSWER: Favored conformation of peptide bonds is with the sequential alpha carbons
in cis position.
Correct: Trans position
Which of the following amino acids is found most frequently at beta turns in the
secondary structures of proteins? - ANSWER: Proline
Which of the following secondary structures is most likely to be found in a membrane
embedded portion of a protein? - ANSWER: An alpha helix composed entirely of
hydrophobic residues
The amino acid that would be expected to be located within the interior of a folded
protein suspended in an aqueous buffer would be - ANSWER: Isoleucine because it's
non polar
The amino acid that would disrupt the ordered structure of a folded alpha helix would be
- ANSWER: Proline because of the compound formation
The amino acid that could be modified by addition of a phosphate group would be -
ANSWER: Tyrosine because of the aromatic ring
A histidine residue is in the active site of an enzyme and has a glutamate residue
nearby, What effect would the nearby glutamate have on the pea of the histidine? -
ANSWER: Glutamate is an acidic amino acid because it has a negative charge and
would favor a positively charged amino acid like Histidine.
Favoring a positively charged form makes histidine a weaker acid causing the pka to go
up.
Experiments on denaturation and renaturation after the reduction and deoxidation of the
disulfide bonds in the enzyme RNase have shown that: - ANSWER: the primary
sequence of RNase is sufficient to determine its specific secondary and tertiary
structure
The side chain of serine could interact with the side chain of ________ using a
________ - ANSWER: His, hydrogen bond
, For a globular protein that is found in the cytosol, ___ would most likely be found in the
proteins interior while ___ would most likely be found on the surface. - ANSWER: Leu,
Ser
Which of the following interactions would be involved in quaternary structure? -
ANSWER: Hydrogen bonds, hydrophobic interactions, disulfide bonds, and salt bridges
In a site directed mutagenesis experiment a specific Leu residue in a protein was
changed to various other residues. Predict which if the following changed would have
the greatest impact on the structure and function of the protein. - ANSWER: Asp
Which of the following is the driving force for protein folding? - ANSWER: Hydrophobic
effect
Molecular chaperones assist unfolded proteins by - ANSWER: Protecting the unfolded
protein from inappropriate protein protein interactions as the protein is synthesized .
Inducing rapid and precise folding of proteins into their correct conformations
Protein domains are - ANSWER: independently folded regions with a tertiary function,
often with a specific and unique function
Amino acids with R groups that have H-bond potential are - ANSWER: Serine,
Glutamate, Tyrosine and threonine (all have OH groups)
A Ramachandran plot shows: - ANSWER: shows the favored and disfavored phi and psi
angles.
pH < pKa - ANSWER: favors COOH and NH3+
pH > pKa - ANSWER: favors COO- and NH2
Hydrogen bond donor - ANSWER: N-H group (positive charge)
Hydrogen acceptor - ANSWER: C=O group (negative charge)
Phi angle (Φ): - ANSWER: angle of rotation about the single bond between the nitrogen
and the alpha carbon atom
Psi angle (Ψ): - ANSWER: angle of rotation about the single bond between the alpha
carbon and the carbonyl carbon atom
Petide bond is between - ANSWER: C=O and N-H
Primary structure - ANSWER: The first level of protein structure; the specific sequence
of amino acids making up a polypeptide chain.
