Deck 5: Amino Acids, Peptides, and Proteins

Question 1

The term protein refers to amino acid polymers with greater than ________amino acids.

A) 10
B) 20
C) 50
D) 70
E) 90

Answer 1

C

Question 2

Which of the following is a nonstandard amino acid?

A) Glycine
B) Cysteine
C) 5-Hydroxyproline
D) Valine
E) Alanine

Answer 2

C

Question 3

Which of the following is a heterocyclic amino acid?

A) Alanine
B) Valine
C) Proline
D) Tyrosine
E) Cystine

Answer 3

C

Question 4

Which of the following is not a class of amino acid?

A) Nonpolar and neutral
B) Polar and neutral
C) Acidic
D) Basic
E) Asymmetric

Question 5

Which of the following amino acids lacks a center of asymmetry?

A) Alanine
B) Glycine
C) Valine
D) Isoleucine
E) Aspartic acid

Question 6

Given the following pK's what is the principal form of serine at pH 5?
PK_a1 = 2.21 pK_a2 = 9.15 pK_R = 13

A)
B)
C)
D)
E)

Question 7

Given the following pKa's, the isoelectric point of serine is ________.
PK1 = 2.21 pK2 = 9.15 pK_R = 13

A) 2.21
B) 5.68
C) 9.15
D) 6.62
E) 11.36

Question 8

Consider the following dipeptide. Which letter indicates an amide bond?

A) A
B) B
C) C
D) D
E) E

Question 9

The amino acid sequence of a polypeptide is referred to as ________structure.

A) Primary
B) Secondary
C) Tertiary
D) Quaternary
E) Peptide

Question 10

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

A) Primary
B) Secondary
C) Tertiary
D) Quaternary
E) Peptide

Question 11

Invariant amino acids in a protein are presumed:

A) To be unimportant in the structure and function of the protein
B) To be essential to the structure and function of the protein
C) Always to occur at the beginning of the amino acid sequence of an enzyme
D) Always to occur at the end of the amino acid sequence of an enzyme
E) To be part of the prosthetic group

Question 12

-pleated sheets are associated with what level of protein structure?

A) Primary
B) Secondary
C) Tertiary
D) Quaternary
E) Superquaternary

Question 13

Which of the following amino acids would foster an -helix?

A) Glycine
B) Alanine
C) Proline
D) Tyrosine
E) Serine

Question 14

The Greek key is associated with which of the following?

A) -helix
B) Parallel -pleated sheets
C) Antiparallel -pleated sheets
D) Disulfide bridges
E) Salt bridges

Question 15

Which of the following interactions does not stabilize tertiary structure?

A) Hydrophobic interactions
B) Electrostatic interactions
C) Hydrogen bonds
D) Covalent bonds
E) None of the above

Question 16

Detergents denature proteins by disrupting which of the following?

A) Hydrogen bonds
B) Disulfide bridges
C) Hydrophobic interactions
D) Salt bridges
E) Both A and B are correct

Question 17

Fibrous proteins typically have large amounts of:

A) -Helix
B) -Pleated sheets
C) Disulfide bridges
D) Salt bridges
E) Both A and B are correct

Question 18

The identity and arrangement of amino acids on the surface of a globular protein are important because they may:

A) Interact to form specific binding cavities
B) Stabilize the tertiary structure of the protein
C) Bind regulatory molecules
D) Both A and C are correct
E) All of the above are correct

Question 19

Which of the following statements regarding cooperative binding is true?

A) Two or more proteins aid the binding of a ligand.
B) The binding of one ligand aids the binding of a second ligand
C) The folding of part of a protein aids in the folding of the remainder of the protein
D) All proteins engage in cooperative binding
E) The binding of a cofactor to a protein aids in the binding of a ligand.

Question 20

Which of the following statements is true of the Bohr effect?

A) Oxygen is delivered to cells in proportion to their needs
B) Binding of protons to hemoglobin molecules facilitates the binding of oxygen
C) Metabolic waste products bond to oxyhemoglobin
D) A and B are both true
E) All of the above are true

Question 21

A polypeptide has a high pI value. Which of the following amino acids are likely to be present?

A) Glycine
B) Serine
C) Valine
D) Aspartic acid
E) Arginine

Question 22

Structural proteins "freeze" large amounts of water. Which of the following interactions is not likely to be involved in the binding of water?

A) Salt bridges
B) Hydrogen bonding
C) Hydrophilic interactions
D) Disulfide bridges
E) Both C and D are correct

Question 23

Why is the peptide bond stronger than the ester bond?

A) Greater electronegativity of nitrogen
B) Greater electronegativity of oxygen
C) Resonance stabilization of the amide bond
D) Increased basicity of nitrogen
E) Size of the nitrogen atom compared to the oxygen atom

Question 24

Which of the following amino acids would be classified as a nonstandard amino acid?

A) Tyrosine
B) Lysine
C) Cystine
D) Glycine
E) Arginine

Question 25

Given that pK₁ = 2.35 and pK₂ = 9.69 for alanine. What is its isoelectric point?

A) 9.69
B) 2.34
C) 6.02
D) 12.03
E) 7.00

Question 26

When not at the terminal of a protein, which of the following amino acids cannot contribute to the pI of a protein?

A) Arginine
B) Lysine
C) Cysteine
D) Tyrosine
E) Alanine

Question 27

When part of a polypeptide chain, other than the N-terminus, which of the following amino acids can form an aldimine?

A) Glycine
B) Alanine
C) Proline
D) Histidine
E) Lysine

Question 28

Collagen is classified as which of the following types of protein?

A) Enzyme
B) Structural
C) Movement
D) Defense
E) Regulatory

Question 29

A prosthetic group is a:

A) Repair enzyme
B) Group other than an amino acid that is part of a protein
C) Group that generates the native form of a protein
D) Disulfide link
E) Group that reduces enzyme activity

Question 30

The major component of the dry weight of cells is _______.

A) Carbohydrate
B) Protein
C) Fats
D) Minerals
E) The major component will vary from organism to organism

Question 31

The total number of proteins that can be produced from any 10 amino acids is?

A) 10²⁰
B) 20¹⁰
C) 100
D) 200
E) 10¹⁰

Question 32

Schiff bases are also referred to as:

A) Aldimines
B) Amines
C) Carbinolamines
D) Amino acids
E) Both A and C are correct

Question 33

Which of the following amino acids would be found in a -turn?

A) Proline
B) Alanine
C) Phenylalanine
D) Lysine
E) Tyrosine

Question 34

Which of the following is not a function of IUPs?

A) Signal transduction
B) Transcription
C) Translation
D) Cell proliferation
E) Oxygen transport

Question 35

The source of energy for motor proteins in addition to ATP is:

A) NAD⁺
B) GTP
C) PEP
D) ADP
E) PP_i

Question 36

Keratin is classified as which of the following types of protein?

A) Enzyme
B) Structural
C) Movement
D) Defense
E) Regulatory

Question 37

In which of the following mechanical properties does spider silk exceed all synthetic fibers?

A) Toughness
B) Tensile strength
C) Elasticity
D) Resilience
E) All of the above

Question 38

Which of the following is a hydrophobic amino acid?

A) Glycine
B) Serine
C) Lysine
D) Phenylalanine
E) Both C and D are hydrophobic

Question 39

A conjugated protein consists of a simple protein combined with a _________.

A) Apoprotein
B) Holoprotein
C) Prosthetic group
D) Answers B and C are correct
E) All of the above are correct

Question 40

Which of the following amino acids is not one of the twenty standard amino acids?

A) Glycine
B) Phenylalanine
C) Tyrosine
D) Cystine
E) Arginine

Question 41

How many octapeptides containing only two amino acids are possible?

A) 8
B) 148
C) 16
D) 256
E) 35

Question 42

Amino acid polymers with a molecular weight between several thousand and several million Daltons are called

A) Dipeptides
B) Polypeptides
C) Proteins
D) Peptides
E) None of the above

Question 43

Which of the following is a polar amino acid?

A) Phenylalanine
B) Tyrosine
C) Methionine
D) Tryptophan
E) Proline

Question 44

Describe the term protomer.

Question 45

What is a zwitterion?

Question 46

Describe the term hormone. Give an example.

Question 47

What is a Schiff base? Give an example of a reaction involving a Schiff base.

Question 48

What is a moonlighting protein? Give an example.

Question 49

Define the term molecular disease.

Question 50

In what level of protein structure do disulfide bond occur?

Question 51

What type of secondary structure would the following amino acid sequence be most likely to have ?
Ala-Val-Ala-Val-Ala-Val-

Question 52

What type of secondary structure would poly-L form? What type of structures would poly-D-alanine form?

Question 53

Why do some proteins require molecular chaperones to fold into their active conformations, while others do not?

Question 54

Of the naturally occurring amino acids Gly, Val, Phe, His, and Ser, which would be likely to form coordination compounds with metals when part of a peptide chain?

Question 55

Which amino acid is the precursor of the following molecule called serotonin?

Question 56

Which amino acid is the precursor of the following molecule called dopamine.

Question 57

The peptide bond is a stronger bond than that of esters. What structural feature of the peptide bond gives it additional bond strength?

Question 58

What would be the products of the acid hydrolysis of the following decapeptide?
Gly-Phe-Tyr-Asn-Tyr-Met-Ser-His-Val-Leu

Question 59

A polypeptide has a high pI value. Suggest which amino acids might comprise it.

Question 60

Distinguish between proteins, peptides and polypeptides.

Question 61

Describe the forces involved in protein folding.

Question 62

The amino acid glutamine is not isolated when proteins containing glutamine are hydrolysed in acid or base. Explain.

Question 63

Hydrolysis of proteins containing cysteine often produce considerable amounts of cystine on hydrolysis. Explain.

Question 64

Which of the standard amino acids would not survive acid hydrolysis?

Question 65

Tryptophan is the precursor of serotonin. What chemical reaction must take place to effect this change?

Question 66

A mutational change alters a polypeptide by substituting three adjacent prolines for three glycines. What possible effect will this event have on the proteins structure?

Question 67

Proteins containing L-amino acids form right-handed helices, whereas proteins containing D-amino acids form left-handed helices. Would a racemic mixture (equal amounts of D and L-amino acids) form a helix?

Question 68

Phosphoserine is a modified amino acid. How many inflection points would there be in a titration of this molecule?
Phosphoserine

Question 69

Mutations in protein structure are either lethal, inconsequential or beneficial. Explain.

Question 70

Is it possible for a multifunctional protein to improve its activity for one function without affecting the activity of another function?

Question 71

The initial estimate for protein coding genes in humans was 100,000 instead of the approximately 20,000 genes that have been confirmed. What factors explain this discrepancy?

Question 72

Arginine has the following pKa values
pK₁ = 2.17 , pK₂ = 9.04 pK_R = 12.48
Give the net charge at the following pH's 1, 2, 4, 7, 10

Question 73

Consider the following tripeptide
Gly-Ala-Val
Glycine pK₁ = 2.34 pK₂ = 9.60 Alanine pK₁ = 2.34 pK₂ = 9.69
Valine pK₁ = 2.32 pK₂ = 9.62
-What is its approximate isoelectric point of this molecule?

Question 74

Consider the following tripeptide
Gly-Ala-Val
Glycine pK₁ = 2.34 pK₂ = 9.60 Alanine pK₁ = 2.34 pK₂ = 9.69
Valine pK₁ = 2.32 pK₂ = 9.62
-In which direction will the tripeptide move if placed in an electric field at pH 1, 5, 10, and 12

Question 75

The pKa values for tyrosine are as follows:
pK₁ 2.20 pK₂ 9.11 pK_R 10.07
What is the pI of tyrosine?