Question 1

What factors would make it difficult to interpret the results of a gel electrophoresis of proteins in the absence of sodium dodecyl sulfate (SDS)?

Accepted Answer

Sodium dodecyl sulfate (SDS) is an anion...

Question 2

Which item is NOT a biochemical use/function of peptides of small molecular weight?

Accepted Answer

A)   artificial sweetener
B)   hormone
C)   poison
D)   antibiotics
E)   All of the answer choices are correct.F) A) and D)
G) None of the above

Question 3

By convention, polypeptides are read in which order?

Accepted Answer

A)   N- to C-terminus
B)   C- to N-terminus
C)   5' to 3'
D)   3' to 5'
E)   smallest to largest amino acid by molecular weightF) A) and B)
G) A) and C)

Question 4

The first step in two-dimensional gel electrophoresis generates a series of protein bands by isoelectric focusing. In a second step, a strip of this gel is turned 90 degrees, placed on another gel containing SDS, and electric current is again applied. In this second step:

Accepted Answer

A)   proteins with similar isoelectric points become further separated according to their molecular weights.
B)   the individual bands become stained so that the isoelectric focus pattern can be visualized.
C)   the individual bands become visualized by interacting with protein-specific antibodies in the second gel.
D)   the individual bands undergo a second, more intense isoelectric focusing.
E)   the proteins in the bands separate more completely because the second electric current is in the opposite polarity to the first current.F) A) and B)
G) C) and E)

Question 5

The gel below illustrates the purification of the RecA protein from E. coli. This gel was loaded from the top. Which statement BEST describes how proteins "run" in an SDS gel?

Accepted Answer

A)   The proteins are separated primarily by molecular weight-the largest MW proteins are on the bottom, and the smallest are on the top.
B)   The proteins are separated primarily by molecular weight-the smallest MW proteins are on the bottom, and the largest are on the top.
C)   The proteins are separated primarily by charge-the protein with the smallest pI is on the top, and the protein with the largest pI is on the bottom.
D)   The proteins are separated primarily by charge-the protein with the largest pI is on the top, and the protein with the smallest pI is on the bottom.
E)   The proteins are separated primarily by their propensity to precipitate-as electrophoresis progresses, the heat generated by the current denatures proteins faster or slower. The slowest to denature is on the bottom, and the fastest to denature is on the top.F) All of the above
G) A) and B)

Question 6

The average molecular weight of the 20 standard amino acids is 138, but biochemists use 110 when estimating the number of amino acids in a protein of known molecular weight. Why?

Accepted Answer

A)   The number 110 is based on the fact that the average molecular weight of a protein is 110,000 with an average of 1000 amino acids.
B)   The number 110 reflects the higher proportion of small amino acids in proteins, as well as the loss of water when the peptide bond forms.
C)   The number 110 reflects the number of amino acids found in the typical small protein, and only small proteins have their molecular weight estimated this way.
D)   The number 110 takes into account the relatively small size of nonstandard amino acids.
E)   The number 138 represents the molecular weight of conjugated amino acids.F) A) and C)
G) B) and D)

Question 7

What are the structural characteristics common to all amino acids found in naturally occurring proteins?

Accepted Answer

All amino acids found in naturally occur...

Question 8

How are sequential reactions controlled in the Edman degradation procedure?

Accepted Answer

A)   A high salt step is followed by a low salt step.
B)   A low salt step is followed by a high salt step.
C)   A high pH step is followed by a low pH step.
D)   A low pH step is followed by a high pH step.
E)   None of the answers is correct.F) B) and C)
G) B) and E)

Question 9

The MOST useful way to classify amino acids is by:

Accepted Answer

A)   molecular weight.
B)   pKa.
C)   polarity.
D)   propensity in proteins.
E)   alphabetical order.F) B) and D)
G) C) and D)

Question 10

The pKa of lysine's carboxyl group, amino group, and side chain are 2.2, 9.0, and 10.5, respectively. If lysine is in a pH 13 solution, what is the net charge on each lysine molecule?

Accepted Answer

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

Question 11

The "signature sequence" shown below represents a portion of a protein from four different organisms.  a. At which position(s) are amino acid residues invariant?
b. At which position(s) are amino acids limited to positively charged residues?
c. At which position(s) are amino acids limited to negatively charged residues?
d. At which position(s) are amino acids limited to nonpolar residues?

Accepted Answer

The answer of The "signature sequence" shown below represents a...

Question 12

Prosthetic groups in the class of proteins known as glycoproteins are composed of:

Accepted Answer

A)   carbohydrates.
B)   flavin nucleotides.
C)   lipids.
D)   metals.
E)   phosphates.F) B) and C)
G) D) and E)

Question 13

For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will have:

Accepted Answer

A)   a net negative charge.
B)   a net positive charge.
C)   no charged groups.
D)   no net charge.
E)   positive and negative charges in equal concentration.F) C) and E)
G) A) and E)

Question 14

You are given a solution containing an enzyme that converts B into A. Describe what you would do to determine the specific activity of this enzyme solution.

Accepted Answer

To determine the specific activity of th...

Question 15

In the amino acid glycine, what effect does the positively charged -NH3+ group have on the pKa of an amino acid's -COOH group?

Accepted Answer

In the amino acid glycine, the positivel...

Question 16

What does the molecule SDS do to proteins?

Accepted Answer

A)   It neutralizes any charged residues on the protein.
B)   It denatures large portions of proteins.
C)   It distributes a large negative charge throughout the protein.
D)   It neutralizes any charged residues on the protein and denatures large portions of proteins.
E)   It denatures large portions of proteins and distributes a large negative charge throughout the protein.F) B) and E)
G) D) and E)

Question 17

A biochemist wishes to determine the sequence of a protein that contains 123 amino acid residues. After breaking all of the disulfide bonds, the protein is treated with cyanogen bromide (CNBr), and it is determined that that this treatment breaks up the protein into seven conveniently sized peptides, which are separated from each other. It is your turn to take over. Outline the steps you would take to determine, unambiguously, the sequence of amino acid residues in the original protein.

Accepted Answer

1. First, I would isolate each of the se...

Question 18

The amino acid proline is unique because the R group:

Accepted Answer

A)   has a phosphate attached.
B)   is cyclical.
C)   is attached to the carboxylic acid carbon.
D)   is positively charged.
E)   None of the answers is correct.F) A) and B)
G) B) and D)

Question 19

Iodoacetamides, maleimides, benzyl halides, and bromomethyl ketones can all be used to modify the _____ group on _____ residues.

Accepted Answer

A)   amino; basic
B)   phenyl; Tyr and Trp
C)   carboxyl; acidic
D)   sulfhydryl; Cys
E)   hydroxyl; Ser and TyrF) C) and D)
G) A) and D)

Question 20

Amino acids without ionizable R-groups can act as a zwitterion in a(n)  _____ solution.

Accepted Answer

A)   nonpolar
B)   boiling
C)   acidic
D)   basic
E)   neutralF) B) and D)
G) None of the above

Exam 3: Amino Acids, Peptides, and Proteins

The gel below illustrates the purification of the RecA protein from E. coli. This gel was loaded from the top. Which statement BEST describes how proteins "run" in an SDS gel?

Correct Answer
verified

What factors would make it difficult to interpret the results of a gel electrophoresis of proteins in the absence of sodium dodecyl sulfate (SDS)?

Correct Answer
Answered by ExamLex AI
Sodium dodecyl sulfate (SDS) is an anion...
View Answer

Amino acids without ionizable R-groups can act as a zwitterion in a(n) _____ solution.

Correct Answer
verified

In the amino acid glycine, what effect does the positively charged -NH₃⁺ group have on the pK_a of an amino acid's -COOH group?

Correct Answer
Answered by ExamLex AI
In the amino acid glycine, the positivel...
View Answer

The MOST useful way to classify amino acids is by:

Correct Answer
verified

The pK_a of lysine's carboxyl group, amino group, and side chain are 2.2, 9.0, and 10.5, respectively. If lysine is in a pH 13 solution, what is the net charge on each lysine molecule?

Correct Answer
verified

For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will have:

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
1. First, I would isolate each of the se...
View Answer

The amino acid proline is unique because the R group:

Correct Answer
verified

You are given a solution containing an enzyme that converts B into A. Describe what you would do to determine the specific activity of this enzyme solution.

Correct Answer
Answered by ExamLex AI
To determine the specific activity of th...
View Answer

The average molecular weight of the 20 standard amino acids is 138, but biochemists use 110 when estimating the number of amino acids in a protein of known molecular weight. Why?

Correct Answer
verified

What does the molecule SDS do to proteins?

Correct Answer
verified

By convention, polypeptides are read in which order?

Correct Answer
verified

The first step in two-dimensional gel electrophoresis generates a series of protein bands by isoelectric focusing. In a second step, a strip of this gel is turned 90 degrees, placed on another gel containing SDS, and electric current is again applied. In this second step:

Correct Answer
verified

Prosthetic groups in the class of proteins known as glycoproteins are composed of:

Correct Answer
verified

What are the structural characteristics common to all amino acids found in naturally occurring proteins?

Correct Answer
Answered by ExamLex AI
All amino acids found in naturally occur...
View Answer

Which item is NOT a biochemical use/function of peptides of small molecular weight?

Correct Answer
verified

Correct Answer
verified

Iodoacetamides, maleimides, benzyl halides, and bromomethyl ketones can all be used to modify the _ group on _ residues.

Correct Answer
verified

How are sequential reactions controlled in the Edman degradation procedure?

Correct Answer
verified

Exam 3: Amino Acids, Peptides, and Proteins

The gel below illustrates the purification of the RecA protein from E. coli. This gel was loaded from the top. Which statement BEST describes how proteins "run" in an SDS gel?

Correct AnswerverifiedShow Answer

What factors would make it difficult to interpret the results of a gel electrophoresis of proteins in the absence of sodium dodecyl sulfate (SDS)?

Correct AnswerAnswered by ExamLex AISodium dodecyl sulfate (SDS) is an anion...View AnswerShow Answer

Amino acids without ionizable R-groups can act as a zwitterion in a(n) _____ solution.

Correct AnswerverifiedShow Answer

In the amino acid glycine, what effect does the positively charged -NH3+ group have on the pKa of an amino acid's -COOH group?

Correct AnswerAnswered by ExamLex AIIn the amino acid glycine, the positivel...View AnswerShow Answer

The MOST useful way to classify amino acids is by:

Correct AnswerverifiedShow Answer

The pKa of lysine's carboxyl group, amino group, and side chain are 2.2, 9.0, and 10.5, respectively. If lysine is in a pH 13 solution, what is the net charge on each lysine molecule?

Correct AnswerverifiedShow Answer

For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will have:

Correct AnswerverifiedShow Answer

Correct AnswerAnswered by ExamLex AI1. First, I would isolate each of the se...View AnswerShow Answer

The amino acid proline is unique because the R group:

Correct AnswerverifiedShow Answer

You are given a solution containing an enzyme that converts B into A. Describe what you would do to determine the specific activity of this enzyme solution.

Correct AnswerAnswered by ExamLex AITo determine the specific activity of th...View AnswerShow Answer

The average molecular weight of the 20 standard amino acids is 138, but biochemists use 110 when estimating the number of amino acids in a protein of known molecular weight. Why?

Correct AnswerverifiedShow Answer

What does the molecule SDS do to proteins?

Correct AnswerverifiedShow Answer

By convention, polypeptides are read in which order?

Correct AnswerverifiedShow Answer

The first step in two-dimensional gel electrophoresis generates a series of protein bands by isoelectric focusing. In a second step, a strip of this gel is turned 90 degrees, placed on another gel containing SDS, and electric current is again applied. In this second step:

Correct AnswerverifiedShow Answer

Prosthetic groups in the class of proteins known as glycoproteins are composed of:

Correct AnswerverifiedShow Answer

What are the structural characteristics common to all amino acids found in naturally occurring proteins?

Correct AnswerAnswered by ExamLex AIAll amino acids found in naturally occur...View AnswerShow Answer

Which item is NOT a biochemical use/function of peptides of small molecular weight?

Correct AnswerverifiedShow Answer

Correct AnswerverifiedShow Answer

Iodoacetamides, maleimides, benzyl halides, and bromomethyl ketones can all be used to modify the _____ group on _____ residues.

Correct AnswerverifiedShow Answer

How are sequential reactions controlled in the Edman degradation procedure?

Correct AnswerverifiedShow Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
Sodium dodecyl sulfate (SDS) is an anion...
View Answer

Correct Answer
verified

In the amino acid glycine, what effect does the positively charged -NH₃⁺ group have on the pK_a of an amino acid's -COOH group?

Correct Answer
Answered by ExamLex AI
In the amino acid glycine, the positivel...
View Answer

Correct Answer
verified

The pK_a of lysine's carboxyl group, amino group, and side chain are 2.2, 9.0, and 10.5, respectively. If lysine is in a pH 13 solution, what is the net charge on each lysine molecule?

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
1. First, I would isolate each of the se...
View Answer

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
To determine the specific activity of th...
View Answer

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
verified

Correct Answer
Answered by ExamLex AI
All amino acids found in naturally occur...
View Answer

Correct Answer
verified

Correct Answer
verified

Iodoacetamides, maleimides, benzyl halides, and bromomethyl ketones can all be used to modify the _ group on _ residues.

Correct Answer
verified

Correct Answer
verified