Question 1

Why is dicyclohexylcarbodiimide (DCC) used in peptide synthesis?

Accepted Answer

A)  DCC "protects" the amino group of the intended N-terminal amino acid.
B)  DCC activates the carboxyl group of one amino acid so that this amino acid reacts more readily with a second amino acid.
C)  DCC cleaves the blocking groups from the final peptide.
D)  DCC is the resin used in the automated synthesis of peptides.
E)  DCC removes the peptide from the resin at the conclusion of the synthesis.F) A) and D)
G) B) and E)

Question 2

Which amino acid of a polypeptide would become labeled when the polypeptide is treated with 2,4-dinitrofluorobenzene in base,even though the amino acid is not a terminal amino acid?

Accepted Answer

A)  Lysine
B)  Glycine
C)  Alanine
D)  Phenylalanine
E)  LeucineF) A) and B)
G) All of the above

Question 3

Which of these natural amino acids,when present in a polypeptide,is not likely to exhibit significant hydrogen bonding through its side chain?

Accepted Answer

A)  Leucine
B)  Threonine
C)  Tyrosine
D)  Serine
E)  All of these are likely to exhibit significant hydrogen bonding through the side chain.F) C) and E)
G) C) and D) A

Question 4

Amino acids can be prepared from aldehydes by treatment with ammonia and HCN followed by hydrolysis.This method is known as the ___.

Accepted Answer

The answer of Amino acids can be prepared from aldehydes...

Question 5

Which of these are methods to determine the sequence of amino acids in a peptide?

Accepted Answer

A)  Ladder sequencing; partial hydrolysis and sequence comparison.
B)  Partial hydrolysis; tandem mass spectrometry and IR.
C)  Partial hydrogenolysis and mass spectrometry.
D)  Edman's degradation and NMR.
E)  DNFB in acid,Edman's degradation and labeling.F) D) and E)
G) C) and D)

Question 6

Peptide synthesis has four basic steps.These are: ___.

Accepted Answer

protect the N-terminus,activat...

Question 7

How many different tripeptides can exist,each containing one residue of glycine,one of l-threonine,and one of l-arginine?

Accepted Answer

A)  2
B)  3
C)  6
D)  8
E)  9F) B) and D)
G) A) and B)

Question 8

What might be concluded upon determining that an unknown amino acid has its isoelectric point near pH 3?

Accepted Answer

A)  It must have a hydrophobic side chain.
B)  It must have a hydrophilic side chain.
C)  Its side chain must contain a basic group.
D)  Its side chain must contain more acidic groups then basic groups.
E)  None of these choices is a valid conclusion.F) C) and E)
G) A) and C)

Question 9

What is the induced fit in an enzyme?

Accepted Answer

A)  It is the formation of hydrogen bonding between the enzyme and substrate.
B)  It is a change of secondary structure of the enzyme before binding the substrate.
C)  It is a conformational change produced upon binding of the substrate.
D)  It is a change in quaternary structure of the enzyme to produce the catalysis.
E)  It is the change in the substrate after the catalytic reaction took place.F) B) and D)
G) B) and C)

Question 10

What type of column chromatography packing is commonly used to separate amino acids by HPLC?

Accepted Answer

Cation-exc...

Question 11

Draw the structures of the following amino acids as they would appear in solution of pH = 3.
a)lysine,
b)glutamic acid,
c)alanine,
d)glycine.

Accepted Answer

The answer of Draw the structures of the following amino...

Question 12

Which of these natural amino acids contains a pyrrolidine ring?

Accepted Answer

A)  Phenylalanine
B)  Tyrosine
C)  Tryptophan
D)  4-Hydroxyproline
E)  SerineF) A) and D)
G) A) and C) D

Question 13

Logically,the following "unnatural" amino acid would be substituted for which natural amino acid in the synthesis of peptide analogs?

Accepted Answer

A)  Leucine
B)  Lysine
C)  Arginine
D)  Alanine
E)  ValineF) B) and D)
G) A) and B)

Question 14

Which amino acid would not have its isoelectric point in the pH range 5-7?

Accepted Answer

A)  Leucine
B)  Threonine
C)  Methionine
D)  Arginine
E)  CysteineF) A) and D)
G) A) and C)

Question 15

The hormone that regulates glucose metabolism is called ___.Deficiency of this hormone is the major cause of ___.

Accepted Answer

The answer of The hormone that regulates glucose metabolism is...

Question 16

What might be concluded upon determining that an unknown amino acid has its isoelectric point near pH 10?

Accepted Answer

A)  It must have a hydrophobic side chain.
B)  It must have a hydrophilic side chain.
C)  Its side chain must contain more basic groups then acidic groups.
D)  Its side chain must contain an acidic group.
E)  None of these choices is a valid conclusion.F) C) and D)
G) C) and E)

Question 17

Show the structures of the products obtained on reaction of valine with ninhydrin.

Accepted Answer

The answer of Show the structures of the products obtained...

Question 18

Which of these amino acids has the R configuration at the stereogenic center but,nonetheless,is an L amino acid?

Accepted Answer

A)  I
B)  II
C)  III
D)  IV
E)  VF) All of the above
G) None of the above

Question 19

The 22 $\alpha$-amino acids can be subdivided into three different types on the basis of the structures of their side chains.These three types are: ___.

Accepted Answer

neutral,ac...

Question 20

Which attractive force is responsible for maintaining the tertiary structure of a protein?

Accepted Answer

A)  Disulfide linkages
B)  Hydrogen bonds
C)  van der Waals forces
D)  Hydrophobic interactions
E)  All of these choices.F) B) and C)
G) C) and D)

Exam 24: Amino Acids and Proteins

Why is dicyclohexylcarbodiimide (DCC) used in peptide synthesis?

Correct AnswerverifiedShow Answer

Which amino acid of a polypeptide would become labeled when the polypeptide is treated with 2,4-dinitrofluorobenzene in base,even though the amino acid is not a terminal amino acid?

Correct AnswerverifiedShow Answer

Which of these natural amino acids,when present in a polypeptide,is not likely to exhibit significant hydrogen bonding through its side chain?

Correct AnswerverifiedA

Amino acids can be prepared from aldehydes by treatment with ammonia and HCN followed by hydrolysis.This method is known as the ___.

Correct AnswerverifiedShow Answer

Which of these are methods to determine the sequence of amino acids in a peptide?

Correct AnswerverifiedShow Answer

Peptide synthesis has four basic steps.These are: ___.

Correct Answerverifiedprotect the N-terminus,activat...View AnswerShow Answer

How many different tripeptides can exist,each containing one residue of glycine,one of l-threonine,and one of l-arginine?

Correct AnswerverifiedShow Answer

What might be concluded upon determining that an unknown amino acid has its isoelectric point near pH 3?

Correct AnswerverifiedShow Answer

What is the induced fit in an enzyme?

Correct AnswerverifiedShow Answer

What type of column chromatography packing is commonly used to separate amino acids by HPLC?

Correct AnswerverifiedCation-exc...View AnswerShow Answer

Draw the structures of the following amino acids as they would appear in solution of pH = 3. a)lysine, b)glutamic acid, c)alanine, d)glycine.

Correct Answerverified11eaa4bc_3e4a_d63c_9180_d9eb352662d2_TB5902_00

Which of these natural amino acids contains a pyrrolidine ring?

Correct AnswerverifiedD

Logically,the following "unnatural" amino acid would be substituted for which natural amino acid in the synthesis of peptide analogs?

Correct AnswerverifiedShow Answer

Which amino acid would not have its isoelectric point in the pH range 5-7?

Correct AnswerverifiedShow Answer

The hormone that regulates glucose metabolism is called ___.Deficiency of this hormone is the major cause of ___.

Correct AnswerverifiedShow Answer

What might be concluded upon determining that an unknown amino acid has its isoelectric point near pH 10?

Correct AnswerverifiedShow Answer

Show the structures of the products obtained on reaction of valine with ninhydrin.

Correct AnswerverifiedShow Answer

Which of these amino acids has the R configuration at the stereogenic center but,nonetheless,is an L amino acid?

Correct AnswerverifiedShow Answer

The 22 α\alphaα -amino acids can be subdivided into three different types on the basis of the structures of their side chains.These three types are: ___.

Correct Answerverifiedneutral,ac...View AnswerShow Answer

Which attractive force is responsible for maintaining the tertiary structure of a protein?

Correct AnswerverifiedShow Answer

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protect the N-terminus,activat...
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Cation-exc...
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The hormone that regulates glucose metabolism is called _.Deficiency of this hormone is the major cause of _.

Correct Answer
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The 22 $\alpha$ -amino acids can be subdivided into three different types on the basis of the structures of their side chains.These three types are: ___.

Correct Answer
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neutral,ac...
View Answer

Correct Answer
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