Deck 19: Biomolecules: Amino Acids,peptides,and Proteins

Question 1

Refer to the data below to answer the following question.


Refer to instructions.At what pH would you carry out an electrophoresis experiment if you wanted to separate a mixture of lysine,aspartic acid and phenylalanine? Explain.

Answer 1

The optimum pH for the electrophoresis of three amino acids occurs at the isoelectric point of the amino acid intermediate in acidity.At this pH,one amino acid migrates toward the cathode (the least acidic),one migrates toward the anode (the most acidic),and the amino acid intermediate in acidity does not migrate.In this example,electrophoresis at 5.89 allows the maximum separation of the three amino acids.

Question 2

Instructions: Match a term from the list below to each definition.

Answer 2

Question 3

Draw and name the structure of the product of the following reaction. tryptophan

Answer 3

Question 4

Refer to the data below to answer the following question(s).
Porcine dynorphin is a neuropeptide having 17 amino acid residues.Its structure is shown below.
Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln

Refer to instructions.What fragments would result if dynorphin were cleaved by chymotropsin?

Question 5

Define isoelectric point.

Question 6

Match a structure from the list below to each of the following terms.

Question 7

Draw the structure of the product of the following reaction and describe the usefulness of this type of reaction.

Question 8

Refer to the data below to answer the following question(s).
Porcine dynorphin is a neuropeptide having 17 amino acid residues.Its structure is shown below.
Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln

Refer to instructions.Show the steps involved in a synthesis of F-G-I using the Merrifield procedure.

Question 9

Consider the following structure.Based on this structure answer the following question(s).

Refer to instructions.Identify the C-terminal amino acid and the N-terminal amino acid.

Question 10

Which of the following amino acids has an aromatic side chain?

A)isoleucine
B)valine
C)tyrosine
D)threonine

Question 11

Which of the following amino acids would contain the highest concentration of zwitterions at pH 5.90?

A)aspartic acid (pI 2.77)
B)alanine (pI 6.01)
C)lysine (pI 9.74)
D)glutamic acid (pI 3.22)
E)all of these contain approximately equal concentrations of zwitterions

Question 12

Instructions: Consider the following structure.Based on this structure answer the following question(s).
Refer to instructions.How many other peptides could be formed from this same combination of amino acids?

A)3
B)6
C)9
D)12

Question 13

Refer to the data below to answer the following question(s).
Porcine dynorphin is a neuropeptide having 17 amino acid residues.Its structure is shown below.
Tyr-Gly-Gly-Phe-Leu-Arg-Arg-Ile-Arg-Pro-Lys-Leu-Lys-Trp-Asp-Asn-Gln

Refer to instructions.What fragments would result if dynorphin were cleaved by trypsin?

Question 14

Which of the following amino acids contains two stereocenters?

A)isoleucine
B)proline
C)phenylalanine
D)glutamine

Question 15

Which of the following amino acids has a non-polar side chain?

A)histidine
B)arginine
C)glutamine
D)valine

Question 16

Which of the following amino acids is a secondary amine?

A)proline
B)glutamine
C)histidine
D)aspargine

Question 17

Consider the following structure.Based on this structure answer the following question(s).

Refer to instructions.Circle the peptide bonds.

Question 18

Consider the following structure.Based on this structure answer the following question(s).


Refer to instructions.Name the peptide using both the three-letter and one-letter codes.

Question 19

Write the equation for the reaction,using methanol (CH₃OH),that would render the carboxyl group of alanine unreactive.

Question 20

Which of the following amino acids has a sulfur-containing side chain?

A)serine
B)cysteine
C)lysine
D)methionine
E)both b and d

Question 21

How does phenyl isothiocyanate,Ph-N=C=S,react with a peptide in the Edman degradation?

A)the sp carbon acts as an electrophile in a reaction with an amino group of the peptide
B)the sulfur acts as a nucleophile and adds to the carbon of the peptide bond
C)the nitrogen acts as a nucleophile and adds to the carbon of the peptide bond
D)the sp carbon acts as an electrophile in a reaction with a carboxylate of the peptide

Question 22

Identify the aldehyde byproduct that results from the following reaction.

Question 23

To what structural feature does the term "quaternary structure" refer?

A)the sequence of amino acids in proteins
B)the overall folding pattern of proteins
C)the aggregation of polypeptides
D)the conformation of local regions of polypeptides

Question 24

Which of the following tripeptides is not hydrolysed by chymotrypsin?

A)Phe-Lys-Glu
B)Lys-Tyr-Phe
C)Gln-Ser-Phe
D)Gln-Tyr-Ser

Question 25

To what structural feature does the term "primary structure" refer?

A)the sequence of amino acids in proteins
B)the overall folding pattern of proteins
C)the aggregation of polypeptides
D)the conformation of local regions of polypeptides

Question 26

What are the R/S designations of the two stereocenters of L-threonine?

A)2R,3R
B)2R,3S
C)2S,3R
D)2S,3S

Question 27

Which of the following tripeptides is not hydrolysed by trypsin?

A)Glu-Arg-Ser
B)Arg-Glu-Thr
C)Glu-Ser-Arg
D)Lys-Ser-Arg

Question 28

To what structural feature does the term "secondary structure" refer?

A)the sequence of amino acids in proteins
B)the overall folding pattern of proteins
C)the aggregation of polypeptides
D)the conformation of local regions of polypeptides

Question 29

Which of the following dipeptides is L-Cys-L-Ala?

A)
B)
C)
D)

Question 30

An enzyme classified as a ligase would be associated with a reaction than involves the:

A)introduction of a double bond.
B)loss of water.
C)loss of carbon dioxide.
D)transfer of an amino group.
E)hydrolysis of an ester.

Question 31

Which of the following reagents can be used to cleave a tert-butoxycarbonyl (Boc)protecting group from a peptide?

A)H₂/Pd
B)CF₃CO₂H
C)Na₂CO₃,H₂O
D)LiAlH₄

Question 32

Which of the following dipeptides is L-Ser-L-Phe?

A)
B)
C)
D)

Question 33

Which of the following amino acids migrates to the negative electrode on paper electrophoresis at a pH of 7.0?

A)lysine
B)aspartic acid
C)asparagine
D)glutamic acid

Question 34

Which of the following amino acids migrates to the positive electrode on paper electrophoresis at a pH of 7.0?

A)glutamic acid
B)arginine
C)lysine
D)histadine

Question 35

To what structural feature does the term "tertiary structure" refer?

A)the sequence of amino acids in proteins
B)the overall folding pattern of proteins
C)the aggregation of polypeptides
D)the conformation of local regions of polypeptides

Question 36

Which amino acid results from the following sequence of transformations?