Deck 15: Biomolecules: Amino Acids, Peptides, and Proteins

Question 1

Instructions: Refer to the data below to answer the following question(s).
Leucine is an essential amino acid with the systematic name 2-amino-3-methylpentanoic acid. It has pKa1 = 2.36 and pKa2 = 9.60.
Refer to instructions. Draw the structure of the predominant form of leucine at pH = 1.50.

Answer 1

Question 2

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

An amino acid in its zwitterionic form.

A)
B)
C)Val-Phe-Leu-Met-Tyr-Pro-Gly-Trp-Cys-Glu
D)
E)
F)Asp-Tyr-Ile-His-Pro-Phe-Arg-Val
G)apoenzyme
H)
I)
J)
K)
L)Val-Lys-Phe-Gly-Arg-Met-Arg-Phe
M)vitamins

Answer 2

Question 3

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

A peptide containing eight amino acid residues with a C-terminal valine.

A)
B)
C)Val-Phe-Leu-Met-Tyr-Pro-Gly-Trp-Cys-Glu
D)
E)
F)Asp-Tyr-Ile-His-Pro-Phe-Arg-Val
G)apoenzyme
H)
I)
J)
K)
L)Val-Lys-Phe-Gly-Arg-Met-Arg-Phe
M)vitamins

Answer 3

Asp-Tyr-Ile-His-Pro-Phe-Arg-Val

Question 4

Instructions: Refer to the data below to answer the following question(s).
Leucine is an essential amino acid with the systematic name 2-amino-3-methylpentanoic acid. It has pKa1 = 2.36 and pKa2 = 9.60.
Refer to instructions. Draw the condensed structure for leucine, and label all chirality centers with an asterisk and identify the amine as primary, secondary or tertiary.

Question 5

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 6

Instructions: Refer to the data below to answer the following question(s).
Leucine is an essential amino acid with the systematic name 2-amino-3-methylpentanoic acid. It has pKa1 = 2.36 and pKa2 = 9.60.
Refer to instructions. Leucine is described as an essential amino acid. What does this mean?

Question 7

Instructions: Refer to the data below to answer the following question.

Refer to inatructions. The most acidic amino acid is ____.

Question 8

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

Source from which many coenzymes are derived.

A)
B)
C)Val-Phe-Leu-Met-Tyr-Pro-Gly-Trp-Cys-Glu
D)
E)
F)Asp-Tyr-Ile-His-Pro-Phe-Arg-Val
G)apoenzyme
H)
I)
J)
K)
L)Val-Lys-Phe-Gly-Arg-Met-Arg-Phe
M)vitamins

Question 9

Instructions: Refer to the data below to answer the following question.

Refer to instructions. The most basic amino acid is __________.

Question 10

Instructions: Refer to the data below to answer the following question(s).
Leucine is an essential amino acid with the systematic name 2-amino-3-methylpentanoic acid. It has pKa1 = 2.36 and pKa2 = 9.60.
Refer to instructions. What is the pI of leucine?

Question 11

Instructions: Refer to the data below to answer the following question(s).
Leucine is an essential amino acid with the systematic name 2-amino-3-methylpentanoic acid. It has pKa1 = 2.36 and pKa2 = 9.60.
Refer to instructions. How many possible stereoisomers of leucine are there?

Question 12

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

The product of an Edman degradation.

A)
B)
C)Val-Phe-Leu-Met-Tyr-Pro-Gly-Trp-Cys-Glu
D)
E)
F)Asp-Tyr-Ile-His-Pro-Phe-Arg-Val
G)apoenzyme
H)
I)
J)
K)
L)Val-Lys-Phe-Gly-Arg-Met-Arg-Phe
M)vitamins

Question 13

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

An amino acid with a protected carboxyl group.

A)
B)
C)Val-Phe-Leu-Met-Tyr-Pro-Gly-Trp-Cys-Glu
D)
E)
F)Asp-Tyr-Ile-His-Pro-Phe-Arg-Val
G)apoenzyme
H)
I)
J)
K)
L)Val-Lys-Phe-Gly-Arg-Met-Arg-Phe
M)vitamins

Question 14

Instructions: Refer to the data below to answer the following question(s).
Leucine is an essential amino acid with the systematic name 2-amino-3-methylpentanoic acid. It has pKa1 = 2.36 and pKa2 = 9.60.
Refer to instructions. Draw the structure of the predominant form of leucine at pH = 10.00.

Question 15

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

A polypeptide which gives four fragments on treatment with chymotrypsin.

A)
B)
C)Val-Phe-Leu-Met-Tyr-Pro-Gly-Trp-Cys-Glu
D)
E)
F)Asp-Tyr-Ile-His-Pro-Phe-Arg-Val
G)apoenzyme
H)
I)
J)
K)
L)Val-Lys-Phe-Gly-Arg-Met-Arg-Phe
M)vitamins

Question 16

Instructions: 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.

Question 17

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

A peptide coupling reagent.

A)
B)
C)Val-Phe-Leu-Met-Tyr-Pro-Gly-Trp-Cys-Glu
D)
E)
F)Asp-Tyr-Ile-His-Pro-Phe-Arg-Val
G)apoenzyme
H)
I)
J)
K)
L)Val-Lys-Phe-Gly-Arg-Met-Arg-Phe
M)vitamins

Question 18

Instructions: 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 19

Instructions: Refer to the data below to answer the following question(s).
Leucine is an essential amino acid with the systematic name 2-amino-3-methylpentanoic acid. It has pKa1 = 2.36 and pKa2 = 9.60.
Refer to instructions. Draw a Fischer projection of L-leucine and label the chirality center(s) as R or S.

Question 20

Define isoelectric point.

Question 21

Instructions: 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 22

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 23

Which of the following amino acids is a secondary amine?

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

Question 24

Which of the following tripeptides is not hydrolysed by trypsin?

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

Question 25

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 26

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 27

Instructions: 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 28

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 29

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 30

Match a term from the list below to each definition.

Enzymes which catalyze the bonding together of two substrates.

A)Ligases
B)Fibrous proteins
C)Conjugated protein
D)Hydrolases
E)Simple protein
F)Globular proteins
G)Kinases

Question 31

Match a term from the list below to each definition.

Proteins which are tough and insoluble in water.

A)Ligases
B)Fibrous proteins
C)Conjugated protein
D)Hydrolases
E)Simple protein
F)Globular proteins
G)Kinases

Question 32

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 33

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

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

Question 34

Instructions: Consider the following structure. Based on this structure answer the following question(s).
Refer to instructions. Circle the peptide bonds.

Question 35

Match a term from the list below to each definition.

Enzymes which catalyze the transfer of a phosphate group.

A)Ligases
B)Fibrous proteins
C)Conjugated protein
D)Hydrolases
E)Simple protein
F)Globular proteins
G)Kinases

Question 36

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

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

Question 37

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 38

Match a term from the list below to each definition.

Proteins which coil into compact shapes.

A)Ligases
B)Fibrous proteins
C)Conjugated protein
D)Hydrolases
E)Simple protein
F)Globular proteins
G)Kinases

Question 39

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

Question 40

Instructions: 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 41

During peptide synthesis, the carboxylic acid group may be protected as the methyl ester. Aqueous base hydrolysis is utilized to remove the ester protecting group. Write the complete stepwise mechanism for the hydrolysis of the methyl ester of BOC-Val-Gly-OCH₃, above. Show all intermediate structures and all electron flow with arrows.

Question 42

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 43

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 44

Refer to the data below to answer the following questions:

The octapeptide saralasin is a specific antagonist of angiotensin II. A derivative of saralasin is used therapeutically as an antihypertensive. Amino acid analysis of saralasin show the presence of the following amino acids:

Ala, Arg, His, Pro, Sar, Tyr, Val₂

Refer to instructions. Sar is the mnemonic for sarcosine, N-methyl aminoethanoic acid. Draw the structure of sarcosine.

Question 45

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

Question 46

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 47

Refer to the data below to answer the following questions:

The octapeptide saralasin is a specific antagonist of angiotensin II. A derivative of saralasin is used therapeutically as an antihypertensive. Amino acid analysis of saralasin show the presence of the following amino acids:

Ala, Arg, His, Pro, Sar, Tyr, Val₂

Refer to instructions. Partial hydrolysis of saralasin with dilute hydrochloric acid yields the following fragments:
Tyr-Val-His
Sar-Arg-Val
His-Pro-Ala
Val-Tyr-Val
Arg-Val-Tyr
What is the structure of saralasin?

Question 48

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 49

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 50

BOC protecting groups are generally removed by treatment with trifluoroacetic acid. On the structures provided below, draw arrows consistent with electron flow in the mechanism of this reaction.