Deck 5: Introduction to Proteins: the Primary Level of Protein Structure

Question 1

Which of the following amino acids is incorporated into proteins during ribosomal protein synthesis?

A)sarcosine
B)ornithine
C)4-hydroxyproline
D)phosphoserine
E)selenocysteine

Answer 1

E

Question 2

Which of the following amino acids is derived from another amino acid by the addition of an amine group?

A)lysine
B)asparagine
C)arginine
D)histidine
E)none of the above

Answer 2

B

Question 3

Which of the following events occurs after the formation of disulfide bonds during the conversion of preproinsulin to mature insulin?

A)folding of proinsulin into a stable conformation
B)transport of the molecule through the membranes
C)cleavage of the peptide sequence that joins the A and B chains
D)cleavage of the leader sequence
E)posttranslational modification of specific proline residues

Answer 3

C

Question 4

At a pH of 5, all amino acids have at least ____ charged group(s)and at most, _____ charged group(s).

A)0; 1
B)1; 1
C)1; 2
D)2; 2
E)2; 3

Question 5

What is the sequence of the following peptide?

A)Ile-Ala-Glu
B)Val-Ala-Asp
C)Leu-Gly-Glu
D)Val-Ala-Asn
E)Val-Gly-Gln

Question 6

Given the following peptide, what pair of protease enzymes would be able to produce three smaller peptides? Gly-Ser-Ala-His-Phe-Pro-Asn-Ala-Val-Glu-Cys-Ala-Ser

A)chymotrypsin and thrombin
B)trypsin and chymotrypsin
C)thermolysin and chymotrypsin
D)trypsin and thermolysin
E)none of the above

Question 7

Hydrolysis of a peptide bond produces:

A)an alcohol and an amine
B)an amine and a carboxylic acid
C)a carboxylic acid and an anhydride
D)an amide and a carboxylic acid
E)an alcohol and an amide

Question 8

Which of the following undergoes an oxidation reaction to form a disulfide bond?

A)serine
B)cysteine
C)methionine
D)threonine
E)tyrosine

Question 9

The conversion of ________ represents a conservative change while the conversion of ________ represents a nonconservative change.

A)Asp to Arg; Ile to Ser
B)Tyr to Phe; Lys to Arg
C)Gln to Asn; Ser to Thr
D)Ile to Leu; Asn to Ala
E)Cys to His; Lys to Glu

Question 10

Which of the following is true regarding the $\alpha$ -carbon of an amino acid?

A)there are always four different functional groups attached
B)the most commonly occurring form of amino acids are the D-amino acids
C)when assigning the R-S stereochemistry, the carboxylic acid is always the highest priority functional group
D)for all amino acids except glycine, the $\alpha$ -carbon is a stereocenter
E)none of the above

Question 11

Which of the following pairs of amino acids could form a charge-charge interaction through their R-groups?

A)methionine and histidine
B)glutamine and lysine
C)serine and glutamic acid
D)aspartic acid and arginine
E)threonine and asparagine

Question 12

Which of the following bonds has partial double bond character?

A)1
B)2
C)3
D)4
E)5

Question 13

If a cis peptide bond is found in a protein, the most likely amino acid to contribute the amine to the amide bond is ______.

A)phenylalanine
B)leucine
C)proline
D)glycine
E)arginine

Question 14

Which of the following pairs of amino acids could form a hydrogen bond through their R-groups?

A)serine and phenylalanine
B)aspartic acid and methionine
C)histidine and tyrosine
D)alanine and glutamine
E)leucine and cysteine

Question 15

Of the following amino acids, which will have a pI closest to 3?

A)Cys
B)His
C)Gly
D)Asp
E)Lys

Question 16

At physiological pH, most amino acids are _______, meaning that they contain both a positive and negative charge.

A)zwitterions
B)amphoteric
C)chiral
D)amphipathic
E)none of the above

Question 17

The peptide hormone insulin is composed of two peptide held together primarily by what mechanism?

A)disulfide bonds between cysteine residues
B)charge-charge interactions between acidic and basic amino acids
C)extensive hydrogen bonding due to the relatively high serine and glutamine content
D)hydrophobic interactions
E)an amide bond formed from the R-groups of a glutamic acid residue and a lysine residue

Question 18

The prevalence of the trans orientation in peptide bonds results in the R-groups of adjacent amino acids being oriented approximately ______ degrees with respect to each other.

A)30
B)60
C)90
D)120
E)180

Question 19

Given the following peptide, what would be the overall charge at pH 5? Met-Glu-Ser-Arg-His-Phe-Pro-Asn-Ala-Glu-Cys-Ala-Ser

A)+2
B)+1
C)0
D)-1
E)-2

Question 20

Which of the following pairs of amino acids contains both an aliphatic and an aromatic amino acid?

A)Thr and Tyr
B)Val and Gln
C)Phe and Ile
D)Ser and Cys
E)none of the above

Question 21

What is the pI for the following peptide: Ala-Glu-Val-Asp-Lys-Leu

Question 22

A peptide was treated with protease enzymes and cyanogen bromide followed by complete hydrolysis of the resulting products. Based upon the following data, determine the sequence of the original peptide.
Chymotrypsin gave two peptides containing the following amino acids:
Leu, Pro
Asp, Gln, Arg, Met, Tyr, Val
Cyanogen bromide gave two peptides containing the following amino acids:
Asp, Met
Gln, Leu, Arg, Tyr, Pro, Val
Trypsin gave two peptides containing the following amino acids:
Gln, Leu, Tyr, Pro
Asp, Arg, Met, Val

Question 23

In the sequence of cytochrome c, the presence of cysteine at position 17 in hundreds of different species indicates that this particular amino acid is _________.

A)conserved
B)mutated
C)homologous
D)variable
E)none of the above

Question 24

Draw each of the structures of aspartic acid that predominate at pH 1, 3, 7, and 11.

Question 25

Which of the following pairs of amino acids represents a conservation of the type of amino acid when considering the sequence of a protein from different species?

A)Asp and Asn
B)Lys and His
C)Leu and Val
D)Gly and Ile
E)Phe and Trp