Question 1

How many different combinations can exist for a pentapeptide formed by five different amino acids?

Accepted Answer

The answer of How many different combinations can exist for...

Question 2

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

Accepted Answer

A) Tyrosine 
B) Proline 
C) Tryptophan 
D) Phenylalanine 
E) Histidine 
A) Tyrosine 
B) Proline 
C) Tryptophan 
D) Phenylalanine 
E) Histidine

Question 3

Which of these natural amino acids contains an amide function?

Accepted Answer

A) Asparagine 
B) Proline 
C) Arginine 
D) Histidine 
E) None of these choices. 
A) Asparagine 
B) Proline 
C) Arginine 
D) Histidine 
E) None of these choices.

Question 4

A heptapeptide Ala2,Glu,Phe,Pro,Tyr,Val gives labeled alanine when heated with DNFB followed by hydrolysis.On partial hydrolysis the unlabeled heptapeptide gives the following: Ala·Glu,Pro·Tyr,Ala·Val,Tyr·Ala,Val·Phe·Pro.
What is the amino acid sequence of the heptapeptide?

Accepted Answer

A) Ala·Phe·Pro·Tyr·Ala·Glu·Val 
B) Ala·Val·Phe·Pro·Tyr·Ala·Glu 
C) Ala·Val·Phe·Pro·Tyr·Glu·Ala 
D) Ala·Val·Phe·Tyr·Pro·Ala·Glu 
E) Val·Ala·Phe·Tyr·Pro·Ala·Glu 
A) Ala·Phe·Pro·Tyr·Ala·Glu·Val 
B) Ala·Val·Phe·Pro·Tyr·Ala·Glu 
C) Ala·Val·Phe·Pro·Tyr·Glu·Ala 
D) Ala·Val·Phe·Tyr·Pro·Ala·Glu 
E) Val·Ala·Phe·Tyr·Pro·Ala·Glu

Question 5

Which of the following structures will show the alanine methyl group more deshielded?

Accepted Answer

Alanine because the

Question 6

Draw the structure of the following tripeptide (starting with the N-terminal residue and ending with the C-terminal residue),showing stereochemical details on chirality centers only:
Ala-Ser-Leu

Accepted Answer

The answer of Draw the structure of the following tripeptide...

Question 7

Which of these amino acids is formed from a precursor amino acid only after the latter has been incorporated into a polypeptide chain?

Accepted Answer

A) Serine 
B) Arginine 
C) Isoleucine 
D) Tryptophan 
E) Hydroxyproline 
A) Serine 
B) Arginine 
C) Isoleucine 
D) Tryptophan 
E) Hydroxyproline

Question 8

Give the names of three digestive enzymes secreted by the pancreas.

Accepted Answer

Chymotryps

Question 9

What are the name and the structure of the products A and B? Give the IUPAC for A and the trivial name for B.

Accepted Answer

The answer of What are the name and the structure...

Question 10

Why is this sequence,CH2=CHCH2OH + HBr,then CrO3/H2SO4/H2O,finally excess NH3,not a good method for the preparation of l-alanine?

Accepted Answer

A) NH3 is not sufficiently nucleophilic to perform the final step. 
B) HBr does not add to substituted alkenes. 
C) 1° alcohols are not oxidized by CrO3 in acidic solution. 
D) Initial HBr addition produces a racemic intermediate which leads to racemic product. 
E) Steric hindrance precludes nucleophilic substitution at a 2° carbon atom. 
A) NH3 is not sufficiently nucleophilic to perform the final step. 
B) HBr does not add to substituted alkenes. 
C) 1° alcohols are not oxidized by CrO3 in acidic solution. 
D) Initial HBr addition produces a racemic intermediate which leads to racemic product. 
E) Steric hindrance precludes nucleophilic substitution at a 2° carbon atom.

Question 11

Which of these natural amino acids contains an amide function?

Accepted Answer

A) Asparagine 
B) Glutamine 
C) Methionine 
D) Cysteine 
E) Two of these 
A) Asparagine 
B) Glutamine 
C) Methionine 
D) Cysteine 
E) Two of these

Question 12

This reagent is used to "protect" the amino group of an amino acid which is to be joined to a second amino acid by a peptide bond.

Accepted Answer

A)    
B)    
C)    
D)    
E)    
A)    
B)    
C)    
D)    
E)

Question 13

The predominant form of aspartic acid in water at pH 1 would be:

Accepted Answer

A) I 
B) II 
C) III 
D) IV 
E) V 
A) I 
B) II 
C) III 
D) IV 
E) V

Question 14

Which of the following statements are correct: 
(I)Lysozyme produces hydrolysis of specific acetal linkages in peptidoglycan polymers.
(II)Lysozyme binds the cell wall substrate in a cleft within its tertiary structure.
(III)Evidence suggests sequential SN2 reactions and a covalent enzyme-substrate intermediate.
(IV)One product of the hydrolytic reaction shows inversion of configuration.
(V)The entire lysozyme molecule acts as a leaving group in the cleavage reaction.

Accepted Answer

A) I,II 
B) III,IV 
C) I,II,III,IV 
D) I,II,V 
E) All are correct. 
A) I,II 
B) III,IV 
C) I,II,III,IV 
D) I,II,V 
E) All are correct.

Question 15

Draw structures to represent what happens when lysine is dissolved in a strongly acidic solution (pH=0).

Accepted Answer

The answer of Draw structures to represent what happens when...

Question 16

Which one is the correct reaction sequence for the attachment of valine on the N-terminus of a growing peptide?

Accepted Answer

A) Amino group deprotection,addition of Val and base,heating. 
B) Amino group cleavage on Val,activation of carboxylic acid functionality on growing peptide chain,reaction between the two. 
C) Amino group protection on the growing peptide chain,activation of the carboxylic acid functionality on Val,reaction with growing peptide. 
D) Amino group deprotection on growing peptide,activation of the carboxylic acid functionality on Val,reaction with growing peptide. 
E) Mix Val and growing peptide,add base and incubate the two for a period of time. 
A) Amino group deprotection,addition of Val and base,heating. 
B) Amino group cleavage on Val,activation of carboxylic acid functionality on growing peptide chain,reaction between the two. 
C) Amino group protection on the growing peptide chain,activation of the carboxylic acid functionality on Val,reaction with growing peptide. 
D) Amino group deprotection on growing peptide,activation of the carboxylic acid functionality on Val,reaction with growing peptide. 
E) Mix Val and growing peptide,add base and incubate the two for a period of time.

Question 17

Draw the structures of l-phenylalanine and l-valine in Fischer projection.

Accepted Answer

The answer of Draw the structures of l-phenylalanine and l-valine...

Question 18

Disulfide bonds in proteins:

Accepted Answer

A) result from an oxidation of thiols. 
B) help to maintain the shape of proteins. 
C) can be broken by reduction. 
D) can link two cysteine amino acid residues. 
E) All of these choices. 
A) result from an oxidation of thiols. 
B) help to maintain the shape of proteins. 
C) can be broken by reduction. 
D) can link two cysteine amino acid residues. 
E) All of these choices.

Question 19

The secondary structure of proteins is derived from:

Accepted Answer

A) peptide linkages. 
B) disulfide linkages. 
C) hydrogen bond formation. 
D) hydrophobic interactions. 
E) acid-base interactions. 
A) peptide linkages. 
B) disulfide linkages. 
C) hydrogen bond formation. 
D) hydrophobic interactions. 
E) acid-base interactions.

Question 20

The secondary structure of proteins has three basic types of folding patterns.These are:

Accepted Answer

@#LAT-DLM&-helices,@#LAT-DLM&-

Exam 24: Amino Acids and Proteins

How many different combinations can exist for a pentapeptide formed by five different amino acids?

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

Which of these natural amino acids contains an amide function?

A heptapeptide Ala2,Glu,Phe,Pro,Tyr,Val gives labeled alanine when heated with DNFB followed by hydrolysis.On partial hydrolysis the unlabeled heptapeptide gives the following: Ala·Glu,Pro·Tyr,Ala·Val,Tyr·Ala,Val·Phe·Pro. What is the amino acid sequence of the heptapeptide?

Which of the following structures will show the alanine methyl group more deshielded?

Draw the structure of the following tripeptide (starting with the N-terminal residue and ending with the C-terminal residue),showing stereochemical details on chirality centers only: Ala-Ser-Leu

Which of these amino acids is formed from a precursor amino acid only after the latter has been incorporated into a polypeptide chain?

Give the names of three digestive enzymes secreted by the pancreas.

What are the name and the structure of the products A and B? Give the IUPAC for A and the trivial name for B.

Why is this sequence,CH2=CHCH2OH + HBr,then CrO3/H2SO4/H2O,finally excess NH3,not a good method for the preparation of l-alanine?

Which of these natural amino acids contains an amide function?

This reagent is used to "protect" the amino group of an amino acid which is to be joined to a second amino acid by a peptide bond.

The predominant form of aspartic acid in water at pH 1 would be:

Draw structures to represent what happens when lysine is dissolved in a strongly acidic solution (pH=0).

Which one is the correct reaction sequence for the attachment of valine on the N-terminus of a growing peptide?

Draw the structures of l-phenylalanine and l-valine in Fischer projection.

Disulfide bonds in proteins:

The secondary structure of proteins is derived from:

The secondary structure of proteins has three basic types of folding patterns.These are:

The Basics

Families of Carbon

Acids and Bases

Nomenclature and Conformations of Alkanes and Cycloalkanes

Stereochemistry

Nucleophilic Reactions

Alkenes and Alkynes I

Alkenes and Alkynes II

Nuclear Magnetic Resonance and Mass Spectrometry

Radical Reactions

Alcohols and Ethers

Alcohols From Carbonyl Compounds

Conjugated Unsaturated Systems

Aromatic Compounds

Reactions of Aromatic Compounds

Aldehydes and Ketones

Carboxylic Acids and Their Derivatives

Reactions at the Α Carbon of Carbonyl Compounds

Condensation and Conjugate Addition Reactions of Carbonyl Compounds

Amines

Transition Metal Complexes

Carbohydrates

Lipids

Nucleic Acids and Protein Synthesis

Filters

A heptapeptide Ala₂,Glu,Phe,Pro,Tyr,Val gives labeled alanine when heated with DNFB followed by hydrolysis.On partial hydrolysis the unlabeled heptapeptide gives the following: Ala·Glu,Pro·Tyr,Ala·Val,Tyr·Ala,Val·Phe·Pro. What is the amino acid sequence of the heptapeptide?

Why is this sequence,CH₂=CHCH₂OH + HBr,then CrO₃/H₂SO₄/H₂O,finally excess NH₃,not a good method for the preparation of l-alanine?