Question 1

Of the following bonds, which have freedom of rotation? I. N - C  α\alphaα  
II)  C  α\alphaα   - C
III)  C - N
IV)  R - C  α\alphaα

Accepted Answer

A)   All of them
B)   II, III, and IV
C)   I, II, and IV
D)   I, II, and III
E)   I and IV F) B) and D)
G) None of the above

Question 2

The structural classification of proteins (based on motifs)  is based primarily on their:

Accepted Answer

A)   amino-acid sequence.
B)   evolutionary relationships.
C)   function.
D)   secondary structure content and arrangement.
E)   subunit content and arrangement.F) A) and B)
G) D) and E)

Question 3

A salt bridge would be MOST likely to be found:

Accepted Answer

A)   in the interior of a protein of a bacterium that lives in humans.
B)   on the exterior of a protein of a bacterium that lives in humans.
C)   in the interior of a protein of a thermophilic archaeal organism.
D)   on the exterior of a protein of a thermophilic archaeal organism.
E)   A salt bridge would be equally likely to be found in any of these cases.F) A) and C)
G) None of the above

Question 4

Pauling and Corey's studies of the peptide bond showed that:

Accepted Answer

A)   at pH 7, many different peptide bond conformations are equally probable.
B)   peptide bonds are essentially planar, with no rotation about the C-N axis.
C)   peptide bonds in proteins are unusual, and unlike those in small model compounds.
D)   peptide bond structure is extraordinarily complex.
E)   primary structure of all proteins is similar, although the secondary and tertiary structure may differ greatly.F) None of the above
G) A) and E)

Question 5

The three-dimensional conformation of a protein may be strongly influenced by amino acid residues that are very far apart in sequence. This relationship is in contrast to secondary structure, where the amino acid residues are:

Accepted Answer

A)   always side by side.
B)   generally near each other in sequence.
C)   invariably restricted to about 7 of the 20 standard amino acids.
D)   often on different polypeptide strands.
E)   usually near the polypeptide chain's amino terminus or carboxyl terminus.F) A) and C)
G) B) and D)

Question 6

Pauling and Corey showed that in small peptides, six atoms associated with the peptide bond all lie in a plane. On a dipeptide of two amino acids in trans linkage (side-chains can be shown as -R), which six atoms are part of the planar structure of the peptide bond?

Accepted Answer

In a dipeptide consisting of two amino a...

Question 7

A _____ protein will often have properties that allow it to be both strong and flexible.

Accepted Answer

A)   macromolecular
B)   fibrous
C)   globular
D)   helical
E)   membraneF) B) and C)
G) A) and D)

Question 8

Describe a reservation about the use of x-ray crystallography in determining the three-dimensional structures of biological molecules.

Accepted Answer

One reservation about the use of x-ray c...

Question 9

In an α\alphaα  helix, the R groups on the amino acid residues:

Accepted Answer

A)   alternate between the outside and the inside of the helix.
B)   are found on the outside of the helix spiral.
C)   cause only right-handed helices to form.
D)   generate the hydrogen bonds that form the helix.
E)   stack within the interior of the helix. F) B) and E)
G) None of the above

Question 10

Any given protein is characterized by a unique amino acid sequence (primary structure) and three-dimensional (tertiary) structure. How are these related?

Accepted Answer

The primary structure of a protein refer...

Question 11

Proteostasis is the cellular process by which:

Accepted Answer

A)   proteins are synthesized.
B)   proteins are folded.
C)   proteins are modified.
D)   proteins are degraded.
E)   protein levels are maintained.F) C) and D)
G) B) and E)

Question 12

Which factor is LEAST likely to result in protein denaturation?

Accepted Answer

A)   altering net charge by changing pH
B)   changing the salt concentration
C)   disruption of weak interactions by boiling
D)   exposure to detergents
E)   mixing with organic solvents such as acetoneF) B) and E)
G) A) and B)

Question 13

Which statement concerning protein domains is TRUE?

Accepted Answer

A)   They are a form of secondary structure.
B)   They are examples of structural motifs.
C)   They consist of separate polypeptide chains (subunits) .
D)   They have been found only in prokaryotic proteins.
E)   They may retain their correct shape even when separated from the rest of the protein.F) A) and E)
G) D) and E)

Question 14

In the  α\alphaα  helix, the hydrogen bonds:

Accepted Answer

A)   are roughly parallel to the axis of the helix.
B)   are roughly perpendicular to the axis of the helix.
C)   occur mainly between electronegative atoms of the R groups.
D)   occur only between some of the amino acids of the helix.
E)   occur only near the amino and carboxyl termini of the helix. F) A) and D)
G) A) and C)

Question 15

Explain what is meant by motifs in protein structure.

Accepted Answer

Motifs in protein structure refer to spe...

Question 16

Which image below shows that there are folding intermediates with substantial stability along nearly every folding pathway?

Accepted Answer

A)   I
B)   II
C)   III
D)   IV
E)   None of the answers is correct.F) B) and C)
G) A) and E)

Question 17

Name four factors (bonds or other forces) that contribute to stabilizing the native structure of a protein, and describe one condition or reagent that interferes with each type of stabilizing force.

Accepted Answer

1. Hydrophobic interactions: Hydrophobic...

Question 18

The MOST important contribution to the stability of a protein's conformation appears to be the:

Accepted Answer

A)   entropy increase from the decrease in ordered water molecules forming a solvent shell around it.
B)   maximum entropy increase from ionic interactions between the ionized amino acids in a protein.
C)   sum of free energies of formation of many weak interactions among the hundreds of amino acids in a protein.
D)   sum of free energies of formation of many weak interactions between its polar amino acids and surrounding water.
E)   stabilizing effect of hydrogen bonding between the carbonyl group of one peptide bond and the amino group of another.F) A) and B)
G) A) and C)

Question 19

The secondary structure shown below is an example of a(n) :

Accepted Answer

A)   parallel  β\betaβ  sheet.
B)   antiparallel  β\betaβ  sheet.
C)   right-handed  α\alphaα  helix.
D)   left-handed  α\alphaα  helix.
E)    β\betaβ  turn. F) A) and B)
G) B) and C)

Question 20

Roughly how many amino acids are there in one turn of an  α\alphaα  helix?

Accepted Answer

A)   1
B)   2.8
C)   3.6
D)   4.2
E)   10 F) A) and D)
G) A) and E)

Exam 4: The Three-Dimensional Structure of Proteins

Which factor is LEAST likely to result in protein denaturation?

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Proteostasis is the cellular process by which:

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In the α\alphaα helix, the hydrogen bonds:

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Name four factors (bonds or other forces) that contribute to stabilizing the native structure of a protein, and describe one condition or reagent that interferes with each type of stabilizing force.

Correct AnswerAnswered by ExamLex AI1. Hydrophobic interactions: Hydrophobic...View AnswerShow Answer

In an α\alphaα helix, the R groups on the amino acid residues:

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Of the following bonds, which have freedom of rotation? I. N - C α\alphaα II) C α\alphaα - C III) C - N IV) R - C α\alphaα

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Describe a reservation about the use of x-ray crystallography in determining the three-dimensional structures of biological molecules.

Correct AnswerAnswered by ExamLex AIOne reservation about the use of x-ray c...View AnswerShow Answer

Pauling and Corey's studies of the peptide bond showed that:

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Pauling and Corey showed that in small peptides, six atoms associated with the peptide bond all lie in a plane. On a dipeptide of two amino acids in trans linkage (side-chains can be shown as -R), which six atoms are part of the planar structure of the peptide bond?

Correct AnswerAnswered by ExamLex AIIn a dipeptide consisting of two amino a...View AnswerShow Answer

The MOST important contribution to the stability of a protein's conformation appears to be the:

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Which statement concerning protein domains is TRUE?

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A salt bridge would be MOST likely to be found:

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A _____ protein will often have properties that allow it to be both strong and flexible.

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The secondary structure shown below is an example of a(n) :

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Any given protein is characterized by a unique amino acid sequence (primary structure) and three-dimensional (tertiary) structure. How are these related?

Correct AnswerAnswered by ExamLex AIThe primary structure of a protein refer...View AnswerShow Answer

Explain what is meant by motifs in protein structure.

Correct AnswerAnswered by ExamLex AIMotifs in protein structure refer to spe...View AnswerShow Answer

The three-dimensional conformation of a protein may be strongly influenced by amino acid residues that are very far apart in sequence. This relationship is in contrast to secondary structure, where the amino acid residues are:

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Roughly how many amino acids are there in one turn of an α\alphaα helix?

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Which image below shows that there are folding intermediates with substantial stability along nearly every folding pathway?

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The structural classification of proteins (based on motifs) is based primarily on their:

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In the $\alpha$ helix, the hydrogen bonds:

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1. Hydrophobic interactions: Hydrophobic...
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In an $\alpha$ helix, the R groups on the amino acid residues:

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Of the following bonds, which have freedom of rotation? I. N - C _$\alpha$ II) C _$\alpha$ - C III) C - N IV) R - C _$\alpha$

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One reservation about the use of x-ray c...
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In a dipeptide consisting of two amino a...
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The secondary structure shown below is an example of a(n) : $The secondary structure shown below is an example of a(n) : A) parallel \beta sheet. B) antiparallel \beta sheet. C) right-handed \alpha helix. D) left-handed \alpha helix. E) \beta turn.$

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The primary structure of a protein refer...
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Motifs in protein structure refer to spe...
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Roughly how many amino acids are there in one turn of an $\alpha$ helix?

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