Biochem Final Multiple Choice
Questions
Two proteins that have the same MW but differ in their pI are best separated by:
a. SDS PAGE
b. Dialysis
c. Gel Exclusion Chromotography
d. MALDI MS
e. Carboxymethyl Cation Exchange Chromotography - answersE
When an enzymatic activity is purified from a complex mixture of proteins what usually
happens to the total amount of protein and the specific activity during the purification
process?
a. The total amount of protein and the specific activity both decrease
b. The total amount of protein and the specific activity both increase
c. The total amount of protein decreases and the specific activity increases
d. The total amount of protein increases and the specific activity decreases
e. The total amount of protein decreases and the specific activity remains constant -
answersC
All of the following are true statements about collagen, EXCEPT:
a. Its tertiary structure is stabilized by interstrand hydrogen bonds between backbone
(N-H and C=O)
b. Its primary structure is rich in glycine residues (~1 out of 3)
c. Its structure does not include beta sheets
d. Its tertiary structure consists of two helices that wind around each other
e. It's a strong protein found in connective tissue, bone, and the extracellular matrix -
answersD
Proline has a limited number of allowed conformations compared to other amino acids
because
a. It has a relatively bulky side chain compare to others
b. It is an aliphatic amino acid chain that avoids water contact
, c. Its side chain is linked to the alpha amino group
d. Its side chain has a chiral carbon
e. The alpha amino group is charged along the peptide backbone - answersC
In a stable, right handed alpha helix, the R groups:
a. Tend to contribute to a low PONDR score
b. Project into the interior of the helix
c. Alternate between the outside and the inside of the helix
d. Can form ion pairs if they are at position i and i+2
e. Have a higher tendency to form aggregates than R group in beta sheets
f. Are responsible to the helix dipole - answersA
A Ramachandran plot describes, for a particular amino acid, the sterically permitted
angles for:
a. Rotation about the Calpha-C bond
b. Roation about the N-Calpha bond
c. Rotation about the C-N bond
d. Both a and b
e. Both a and c
f. Both b and c
g. All three: a, b, and c - answersD
L-Dopa is an oral medication used to treat Parkinson's disease, the symptoms which
result from a lack of dopamine in the brain. L-Dopa relies on L-type, or leucine-
preferring, transport proteins to cross the blood-brain barrier, and it is converted to
dopamine in the brain by the enzyme aromatic-L-amino acid decarboxylase. Identify the
properties of its enantiomer D-Dopa. Select ALL that apply:
a. Highly soluble in water
b. Reduces symptoms of Parkinson's disease
c. Rotates plan-polarized light counterclockwise
d. Solid at room temperature
e. Aromatic-L-amino acid decarboxylase has a different affinity for D-Dopa
f. Density is less than that of L-Dopa - answersD
E
Synthetic polypeptides can assume an alpha-helical structure under appropriate
conditions. Indicate which of the following will form an alpha-helix at the indicated pH
values. Circle all that apply:
Polylysine at pH 2
Polylysine at pH 7
Polylysine at pH 13 - answersPolylysine at pH 13
Questions
Two proteins that have the same MW but differ in their pI are best separated by:
a. SDS PAGE
b. Dialysis
c. Gel Exclusion Chromotography
d. MALDI MS
e. Carboxymethyl Cation Exchange Chromotography - answersE
When an enzymatic activity is purified from a complex mixture of proteins what usually
happens to the total amount of protein and the specific activity during the purification
process?
a. The total amount of protein and the specific activity both decrease
b. The total amount of protein and the specific activity both increase
c. The total amount of protein decreases and the specific activity increases
d. The total amount of protein increases and the specific activity decreases
e. The total amount of protein decreases and the specific activity remains constant -
answersC
All of the following are true statements about collagen, EXCEPT:
a. Its tertiary structure is stabilized by interstrand hydrogen bonds between backbone
(N-H and C=O)
b. Its primary structure is rich in glycine residues (~1 out of 3)
c. Its structure does not include beta sheets
d. Its tertiary structure consists of two helices that wind around each other
e. It's a strong protein found in connective tissue, bone, and the extracellular matrix -
answersD
Proline has a limited number of allowed conformations compared to other amino acids
because
a. It has a relatively bulky side chain compare to others
b. It is an aliphatic amino acid chain that avoids water contact
, c. Its side chain is linked to the alpha amino group
d. Its side chain has a chiral carbon
e. The alpha amino group is charged along the peptide backbone - answersC
In a stable, right handed alpha helix, the R groups:
a. Tend to contribute to a low PONDR score
b. Project into the interior of the helix
c. Alternate between the outside and the inside of the helix
d. Can form ion pairs if they are at position i and i+2
e. Have a higher tendency to form aggregates than R group in beta sheets
f. Are responsible to the helix dipole - answersA
A Ramachandran plot describes, for a particular amino acid, the sterically permitted
angles for:
a. Rotation about the Calpha-C bond
b. Roation about the N-Calpha bond
c. Rotation about the C-N bond
d. Both a and b
e. Both a and c
f. Both b and c
g. All three: a, b, and c - answersD
L-Dopa is an oral medication used to treat Parkinson's disease, the symptoms which
result from a lack of dopamine in the brain. L-Dopa relies on L-type, or leucine-
preferring, transport proteins to cross the blood-brain barrier, and it is converted to
dopamine in the brain by the enzyme aromatic-L-amino acid decarboxylase. Identify the
properties of its enantiomer D-Dopa. Select ALL that apply:
a. Highly soluble in water
b. Reduces symptoms of Parkinson's disease
c. Rotates plan-polarized light counterclockwise
d. Solid at room temperature
e. Aromatic-L-amino acid decarboxylase has a different affinity for D-Dopa
f. Density is less than that of L-Dopa - answersD
E
Synthetic polypeptides can assume an alpha-helical structure under appropriate
conditions. Indicate which of the following will form an alpha-helix at the indicated pH
values. Circle all that apply:
Polylysine at pH 2
Polylysine at pH 7
Polylysine at pH 13 - answersPolylysine at pH 13
