Deck 2: Protein Composition and Structure

Question 1

Which amino acid forms disulfide bonds?

A) histidine
B) methionine
C) proline
D) serine
E) cysteine

Answer 1

E

Question 2

Every third residue in the protein collagen is ____________________.

Answer 2

glycine

Question 3

______________________ is the major fibrous protein present in skin, bone, tendon, cartilage, and teeth.

Answer 3

Collagen

Question 4

Disulfide bonds in proteins can be reduced to free sulfhydryl groups by reagents such as _____________________.

Question 5

Key properties of proteins include

A) a wide range of functional groups.
B) an ability to possess either rigid or flexible structures as dictated by functional requirements.
C) the ability to interact with other proteins.
D) All of the answers are correct.
E) a wide range of functional groups and an ability to possess either rigid or flexible structures as dictated by functional requirements.

Question 6

Agents such as ______________________ and guanidinium chloride denature proteins by disrupting the noncovalent interactions.

Question 7

Collagen contains _____________________, a modified amino acid.

Question 8

Which of the following is a function of proteins?

A) energy carrying molecules
B) catalysts
C) storage of genetic information
D) None of the answers is correct.
E) All of the answers are correct.

Question 9

Which of the following amino acids has an ionizable R-group with a pK_a near neutral pH?

A) histidine
B) serine
C) aspartic acid
D) lysine
E) tyrosine

Question 10

The overall three-dimensional structure of a single polypeptide is referred to as _____.

A) primary structure
B) secondary structure
C) tertiary structure
D) quaternary structure
E) both secondary structure and tertiary structure

Question 11

The ________________________ β-sheet structure occurs when the two strands are oriented in the same directions (N →C).

Question 12

_______________ is a fibrous protein and is the primary component of wool and hair.

Question 13

What level of protein structure is composed of $\alpha$ helices, $\beta$ sheets, and turns?

A) primary
B) secondary
C) tertiary
D) quaternary
E) both secondary and tertiary

Question 14

Formation of a peptide bond produces _____ as a byproduct.

A) ammonia
B) carbon dioxide
C) water
D) H⁺
E) OH^-

Question 15

Which of the following is most often found in proteins?

A) D-amino acids
B) L-amino acids
C) an equal amount of D- and L-amino acids
D) amino acids with the $\alpha$ -carbon exclusively having an R absolute configuration
E) amino acids with the $\alpha$ -carbon exclusively having an S absolute configuration

Question 16

What is the charged group(s) present in glycine at a pH of 7?

A) -NH₃⁺
B) -COO^-
C) -NH₂⁺
D) -NH₃⁺ and -COO^-
E) All the charged groups are present.

Question 17

_____________________________ refers to the spatial arrangement of subunits and the nature of their interactions.

Question 18

What type of plot allows one to investigate the likely phi and psi angles of the peptide backbone?

A) Hill
B) Lineweaver-Burk
C) Hanes-Woolf
D) Ramachandran
E) Michaelis-Menten

Question 19

A term that describes a molecule that contains both positive and negative charges but overall has a neutral charge is _____.

A) enantiomer
B) amino acid
C) racemate
D) zwitterion
E) amphipath

Question 20

A protein is considered to be __________________ when it is converted into a randomly coiled structure without its normal activity.

Question 21

Why is the peptide bond planar?

A) Bulky side chains prevent free rotation around the bond.
B) It contains partial double-bond character, preventing rotation.
C) Hydrogen bonding between the NH and C=O groups limits movement.
D) All of the answers are correct.
E) None of the answers is correct.

Question 22

What is the advantage of protein interaction and assembly with other proteins?

Question 23

The configuration of most peptide bonds in a protein is _____.

A) cis
B) circular
C) parallel
D) trans
E) perpendicular

Question 24

Where are Ω and β turns and loops often found?

A) in a hydrophobic pocket
B) on the interior cleft
C) at the protein interface with ligand
D) on the surface of proteins
E) None of the answers is correct.

Question 25

What is the approximate mass of a protein containing 200 amino acids? (Assume there are no other protein modifications.)

A) 2,000
B) 11,000
C) 22,000
D) 222,000
E) None of the answers is correct.

Question 26

How does the protein backbone add to structural stability?

Question 27

What are the three aromatic amino acids?

Question 28

What do the amino acids Tyr, Asn, and Thr have in common?

A) aromatic rings
B) negatively charged at pH 7.0
C) positively charged at pH 7.0
D) double bonds in side chains
E) polar

Question 29

How does a protein's amino acid sequence influence the tertiary structure?

Question 30

What structure(s) did Pauling and Corey predict in 1951?

A) α helix
B) β sheet
C) β turns
D) Pauling and Corey predicted all three of these structures.
E) α helix and β sheet

Question 31

Which individual won a Nobel Prize for his (her) landmark work in sequencing the protein insulin?

A) Pauling
B) McClintock
C) Gilbert
D) Maxam
E) Sanger

Question 32

Which of the following amino acid residues would most likely be buried in the interior of a water-soluble, globular protein?

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

Question 33

Which amino acid side chains are capable of ionization?

Question 34

At a pH of 12, what is the charged group(s) present in glycine?

A) -NH₃⁺
B) -COO^-
C) -NH₂⁺
D) -NH₃⁺ and -COO^-
E) All the charged groups are present.

Question 35

The term "quaternary" with respect to protein structure means

A) a repeating structure stabilized by intrachain hydrogen bonds.
B) the ability to form all four kinds of noncovalent bonds.
C) a multisubunit structure.
D) a linear sequence of four amino acids.
E) None of the answers is correct.

Question 36

Which two amino acids contain a sulfur atom?

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

Question 37

Which of the following pairs of amino acids is positively charged at a neutral pH?

A) Lys, Arg
B) Tyr, Arg
C) Cys, Met
D) Leu, Pro
E) Asp, Glu

Question 38

In the following peptide, which amino acid is the N-terminus?
Phe-Ala-Gly-Arg

A) Phe
B) Ala
C) Gly
D) Arg
E) Phe and Arg

Question 39

What is the advantage of having 20 different amino acids available to form proteins?

Question 40

What are some of the modifications that proteins acquire?

A) cleavage and trimming of the protein
B) addition of carbohydrate groups
C) phosphorylation of certain groups
D) All of these are modifications proteins acquire.
E) addition of carbohydrate groups and phosphorylation of certain groups

Question 41

Why are all the theoretical combinations of phi and psi not possible?

Question 42

$\alpha$ -Keratin is referred to as a coiled-coil protein. Describe the protein structure of $\alpha$ -keratin.

Question 43

What are prions?

Question 44

What is the advantage of having certain areas of partially correct folded regions?

Question 45

Describe some of the features of an α helix.

Question 46

What is the "hydrophobic effect" as it relates to protein structure?

Question 47

In the ribonuclease experiments performed by Anfinsen, what was the significance of the presence of the reducing agent β-mercaptoethanol?

Question 48

What does the modification involving the attachment of acetyl groups to the amino termini of proteins do?