Question 1

If two proteins are determined to have descended from a common ancestor they are

Accepted Answer

A)  heterogeneous.
B)  amphipathic.
C)  taxolinked.
D)  homologous.E) A) and D)
F) B) and C)

Question 2

The overall shape of a protein is greatly influenced by

Accepted Answer

A)  amino acid R group properties.
B)  charged amino acids.
C)  hydrophobic amino acids.
D)  pH.
E)  hydrophilic amino acids.F) D) and E)
G) C) and D)

Question 3

Proline is distinct among the 20 commonly found amino acids because

Accepted Answer

A)  it is a ring compound.
B)  it is hydrophilic and ionic.
C)  the nitrogen of the amino group is in a ring.
D)  the carbon of the carboxyl group is in a ring.
E)  it has little effect on protein structure.F) All of the above
G) D) and E)

Question 4

The liquid that emerges from the bottom of a chromatographic column is called the supernatant.

Accepted Answer

A) True 
 B)False

Question 5

Cystine is likely to be isolated from proteins that are

Accepted Answer

A)  high in methionine.
B)  in the cell nucleus.
C)  intracellular.
D)  extracellular.E) C) and D)
F) A) and C)

Question 6

Match the following to their functions.
-21st amino acid in many species

Accepted Answer

A)  N-formylmethionine
B)  Histamine
C)  S-adenosylmethionine
D)  g-aminobutyrate
E)  selenocysteineF) epinephrine (adrenaline) G) B) and D)
H) B) and E)

Question 7

An enzyme works well at as a catalyst at a pH of 7.2.It is found that catalytic activity is significantly less at a pH of 8.4.Which could likely cause the decrease in activity?

Accepted Answer

A)  The protein has been degraded into its amino acids at pH 8.4.
B)  The protein has changed shape due to a change in charge.
C)  The protonation state of amino acids involved in the catalytic mechanism has changed.
D)  B and C above.
E)  All of the above.F) None of the above
G) A) and B)

Question 8

Ammonium sulfate is often used as a first step in protein purification because it

Accepted Answer

A)  buffers solutions and protects the protein.
B)  precipitates many proteins.
C)  precipitates all proteins.
D)  hydrolyzes proteins into their constituent amino acids.E) A) and C)
F) All of the above

Question 9

Which technique is used less for protein purification and more for the determination of molecular weights?

Accepted Answer

A)  Affinity chromatography.
B)  SDS-PAGE.
C)  Gel filtration.
D)  Ion exchange chromatography.E) A) and B)
F) All of the above

Question 10

Cation-exchange resins have negatively charged groups covalently attached to the column matrix.

Accepted Answer

A) True 
 B)False

Question 11

The pKa's of arginine's α-Carboxyl group,α-Amino group and side chain are 1.8,9.0 and 12.5,respectively.Calculate the isoelectric point.

Accepted Answer

A)  7.8
B)  7.2
C)  10.8
D)  5.4E) A) and B)
F) A) and C)

Question 12

Amino acids and amino acid derivatives can be used to modify proteins.

Accepted Answer

A) True 
 B)False

Question 13

The primary structure of a protein specifically describes the ________.

Accepted Answer

A)  location of disulfide bonds
B)  linear sequence of amino acids
C)  overall three-dimensional shape
D)  Φ and Ψ angles for each amino acidE) None of the above
F) A) and D)

Question 14

Amino acids with non-ionizable side chains are zwitterions when they are ________.

Accepted Answer

A)  in any solution
B)  at physiological pH,pH = 7.4
C)  in acidic solutions only
D)  in alkaline solutions only
E)  All of the aboveF) B) and E)
G) A) and C)

Question 15

A sequence of amino acids with a relatively high hydropathy is very likely to function by

Accepted Answer

A)  being at the active site of an enzyme.
B)  being embedded in a cell membrane.
C)  making a protein soluble.
D)  being on the protein surface.E) A) and B)
F) A) and C)

Question 16

What is the purpose of SDS in SDS-PAGE?

Accepted Answer

A)  To selectively bind the target protein.
B)  To maintain buffer pH in the gel.
C)  To cause the separation to be on the basis of molecular weight only.
D)  To initiate polymerization of acrylamide to form a gel.E) A) and B)
F) C) and D)

Question 17

If the R group of an amino acid is -CH₃,then the name of this compound is

Accepted Answer

A)  methyl amino acid.
B)  2-aminopropanoic acid.
C)  alanine.
D)  All of the above.
E)  B and C.F) All of the above
G) A) and C)

Question 18

For the amino acid lysine,the Henderson-Hasselbalch equation can be applied to ________ ionization group(s) .

Accepted Answer

A)  one
B)  two
C)  three
D)  fourE) All of the above
F) A) and D)

Question 19

What is the net charge on the tripeptide Gly-Arg-Lys at pH 7? The table below gives the pKa's of the ionizable groups on the free amino acids.

Accepted Answer

A)  -1
B)  0
C)  +1
D)  +2E) B) and D)
F) C) and D)

Question 20

The isoelectric point of alanine is pH = 6.15.It is mixed with proline (pHCOOH = 2.0;pHNH₂ = 10.6) ,and the mixture is placed in an electric field at pH 6.15.Which statement is true?

Accepted Answer

A)  The two amino acids will be separated.
B)  The two amino acids will not be separated.
C)  Neither amino acid will move in the electric field.
D)  Both amino acids will move from the origin and be separated.E) A) and D)
F) None of the above

Exam 3: Amino Acids and the Primary Structures of Proteins

An enzyme works well at as a catalyst at a pH of 7.2.It is found that catalytic activity is significantly less at a pH of 8.4.Which could likely cause the decrease in activity?

Correct AnswerverifiedShow Answer

Match the following to their functions. -21st amino acid in many species

Correct AnswerverifiedShow Answer

What is the net charge on the tripeptide Gly-Arg-Lys at pH 7? The table below gives the pKa's of the ionizable groups on the free amino acids.

Correct AnswerverifiedShow Answer

Ammonium sulfate is often used as a first step in protein purification because it

Correct AnswerverifiedShow Answer

Proline is distinct among the 20 commonly found amino acids because

Correct AnswerverifiedShow Answer

Amino acids and amino acid derivatives can be used to modify proteins.

Correct AnswerverifiedShow Answer

If two proteins are determined to have descended from a common ancestor they are

Correct AnswerverifiedShow Answer

Cation-exchange resins have negatively charged groups covalently attached to the column matrix.

Correct AnswerverifiedShow Answer

The liquid that emerges from the bottom of a chromatographic column is called the supernatant.

Correct AnswerverifiedShow Answer

Cystine is likely to be isolated from proteins that are

Correct AnswerverifiedShow Answer

What is the purpose of SDS in SDS-PAGE?

Correct AnswerverifiedShow Answer

The primary structure of a protein specifically describes the ________.

Correct AnswerverifiedShow Answer

A sequence of amino acids with a relatively high hydropathy is very likely to function by

Correct AnswerverifiedShow Answer

For the amino acid lysine,the Henderson-Hasselbalch equation can be applied to ________ ionization group(s) .

Correct AnswerverifiedShow Answer

The pKa's of arginine's α-Carboxyl group,α-Amino group and side chain are 1.8,9.0 and 12.5,respectively.Calculate the isoelectric point.

Correct AnswerverifiedShow Answer

The isoelectric point of alanine is pH = 6.15.It is mixed with proline (pHCOOH = 2.0;pHNH₂ = 10.6) ,and the mixture is placed in an electric field at pH 6.15.Which statement is true?

Correct AnswerverifiedShow Answer

Which technique is used less for protein purification and more for the determination of molecular weights?

Correct AnswerverifiedShow Answer

If the R group of an amino acid is -CH₃,then the name of this compound is

Correct AnswerverifiedShow Answer

The overall shape of a protein is greatly influenced by

Correct AnswerverifiedShow Answer

Amino acids with non-ionizable side chains are zwitterions when they are ________.

Correct AnswerverifiedShow Answer

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