Deck 4: Protein Structure

Question 1

What is the C-terminal amino acid in the pentapeptide Val-Leu-Arg-Ser-Gly?

A) Val
B) Leu
C) Arg
D) Ser
E) Gly

Answer 1

Gly

Question 2

Which of the following structures shows the prevalent form of glutamic acid at pH 3?

A)

B)

C)

D)

E) none of these choices

Answer 2

Question 3

Which of the following structures shows the prevalent form of histidine at pH 5?

A)

B)

C)

D)

E) none of these choices

Answer 3

Question 4

At pH ___, the pentapeptide Ala-Glu-His-Val-Cys would contain two positively charged groups and one negatively charged group.

A) 1
B) 3
C) 5
D) 7
E) 9

Question 5

Which of the following structures shows the prevalent form of cysteine at pH 12?

A)

B)

C)

D)

E) none of these choices

Question 6

What is the net charge of the pentapeptide Ala-Cys-Ser-Glu-Asn at pH 7?

A) -2
B) -3
C) 0
D) +1
E) none of these choices

Question 7

What is the N-terminal residue of the peptide AYSDG?

A) glutamic acid
B) glycine
C) aspartic acid
D) alanine
E) none of these choices

Question 8

If a protein underwent a mutation such that a Glu residue was changed to another amino acid, which of the following amino acids would least likely result in a change in the overall structure of the protein?

A) Ser
B) Asp
C) Gln
D) Lys
E) Ala

Question 9

Since there are 20 standard amino acids, the number of possible linear polypeptides of length N can be expressed as ___.

A)
B)
C)
D)
E)

Question 10

If an $\alpha$ -helical region of a protein contained 18 amino acid residues, how many helical turns would be present?

A) 3.33
B) 4
C) 5
D) 6
E) none of these choices

Question 11

The following is an example of ___.

A) parallel $\alpha$ -helix
B) parallel $\beta$ -sheet
C) antiparallel $\alpha$ -helix
D) antiparallel $\beta$ -sheet
E) none of these choices

Question 12

For a globular protein that is found in the cytosol, ___ would most likely be found in the proteins interior while ___ would most likely be found on the surface.

A) Val; Phe
B) Leu; Ile
C) Leu; Ser
D) Thr; His
E) none of these choices

Question 13

Molecular chaperones assist proteins in the formation of ___.

A) aggregates
B) tertiary structure
C) peptide bonds
D) primary structure
E) none of these choices

Question 14

Given pKa values of 2.3 and 9.7, what is the pI of alanine?

A) 12
B) 7.4
C) 6
D) 4.2
E) none of these choices

Question 15

Given pKa values of 2.1, 9.8 and 3.9 (side chain), what is the pI of aspartic acid?

A) 6.0
B) 6.9
C) 5.3
D) 3.0
E) none of these choices

Question 16

Which of the following methods for cleaving a protein is properly identified?

A) chymotrypsin: cleaves on the C-terminal side of Lys or Arg
B) trypsin: cleaves on the C-terminal side of Ala or Val
C) cyanogen bromide: cleaves on the C-terminal side of Met
D) elastase: cleaves on the C-terminal side of Phe, Trp or Tyr
E) none of these choices

Question 17

What are the products from treatment of the following peptide with chymotrypsin?
Met-Tyr-Ala-Ser-Phe-Val-Lys-Asn-His-Tyr-Gly-Arg-Met-Trp

A) 1 tripeptide, 1 tetrapeptide, 1 pentapeptide, and two free amino acids
B) 1 dipeptide, 1 tripeptide, 1 tetrapeptide and 1 pentapeptide
C) 1 dipeptide, 1 tetrapeptide and 1 octapeptide
D) 1 dipeptide, 2 tripeptides, 1 pentapeptide and one free amino acid
E) none of these choices

Question 18

What are the products from treatment of the following peptide with trypsin?
Leu-Val-Ala-Arg-Phe-Val-Lys-Asn-Leu-Gly-Arg-Cys-Asp

A) 2 dipeptides, 1 tripeptide and 1 tetrapeptide
B) 3 tripeptides and 1 tetrapeptide
C) 2 tripeptides, 1 tetrapeptide and 3 free amino acids
D) 1 dipeptide, 1 tripeptide and 2 tetrapeptides
E) none of these choices

Question 19

A technique for determining protein structure that requires crystals of the protein is ___.

A) NMR spectroscopy
B) X-ray crystallography
C) electron crystallography
D) mass spectrometry
E) none of these choices

Question 20

A technique for determining protein structure where the protein is in solution is ___.

A) NMR spectroscopy
B) X-ray crystallography
C) electron crystallography
D) mass spectrometry
E) none of these choices

Question 21

Hemoglobin contains ___ alpha subunits and ___ beta subunits, thus making hemoglobin a ___ protein.

Question 22

The aggregated proteins seen in Alzheimer's disease and Parkinson's disease are commonly known as ___.

Question 23

A misfolded protein can undergo ___ to attain the native structure or it can undergo ___ to become a plaque.

Question 24

The protein $\alpha$ -synuclein normally forms ___ upon binding to other molecules but forms ___ that lead to amyloid deposits.

Question 25

Transmission spongiform encephalopathies alter ___ protein that impacts the ___ conformation of the protein resulting in aggregates.

Question 26

Draw the predominant structure of valine at pH 10 (pK_as are 2.3 and 9.7).