Deck 13: Proteins: Structure and Function

Question 1

Which of the following types of proteins provides physical support to tissues?

A) receptors
B) structural proteins
C) immunoglobulins
D) transport proteins
E) dietary proteins

Answer 1

structural proteins

Question 2

Which of the following is NOT one of the four categories of biomolecules?

A) proteins
B) vitamins
C) lipids
D) carbohydrates
E) nucleic acids

Answer 2

vitamins

Question 3

An amino acid zwitterion has

A) a net positive charge.
B) a net negative charge.
C) a net neutral charge.
D) any non-neutral charge.
E) Zwitterions can have any charge.

Answer 3

a net neutral charge.

Question 4

In which of the following structures is the box ONLY around the amino acid side chain?

A)a
B)b
C)c
D)d
E)e

Question 5

Physiological pH is a pH of approximately

A) 5.7.
B) 7.3.
C) 8.1.
D) 9.1.
E) 0.

Question 6

Which type of protein signals cellular events?

A) receptors
B) structural proteins
C) immunoglobulins
D) transport proteins
E) dietary proteins

Question 7

What percentage of amino acids in sickle cell hemoglobin is different from normal hemoglobin?

A) 100%
B) 50%
C) 25%
D) 10%
E) <1%

Question 8

Which of the following structures illustrates how an amino acid reacts in a low pH solution?

A)
B)
C)
D)
E)All of these reactions occur to the same extent in a solution with a pH less than 7 .

Question 9

Which of the following choices are the best labels for this amino acid?

A)a
B)b
C)c
D)d
E)e

Question 10

How many naturally occurring amino acids are there?

A) 1
B) 5
C) 10
D) 20
E) hundreds

Question 11

Which of the following choices is NOT a problem associated with sickle-cell anemia?

A) People with sickle-cell anemia are prone to severe headaches.
B) People with sickle-cell anemia are prone to episodes of infection.
C) Organs can be damaged because of sickled red blood cells.
D) Sickle-cell anemia can cause anemia.
E) The sickle cells can aggregate and clog blood vessels.

Question 12

At low pH, the amino acid zwitterion reacts with hydronium (H₃O⁺). What is the product of this acid-base reaction?

A)a
B)b
C)c
D)d
E)e

Question 13

Which of the following structures illustrates an amino acid at physiological pH?

A)a
B)b
C)c
D)d
E)e

Question 14

Hemoglobin is an example of this type of protein.

A) receptors
B) structural proteins
C) immunoglobulins
D) transport proteins
E) dietary proteins

Question 15

Which of the following structures illustrates an amino acid in a solution with a high pH?

A)a
B)b
C)c
D)d
E)e

Question 16

Which of the following structures illustrates an amino acid as a zwitterion?

A)a
B)b
C)c
D)d
E)e

Question 17

Which type of protein can be used for energy when necessary?

A) receptors
B) structural proteins
C) immunoglobulins
D) transport proteins
E) dietary proteins

Question 18

Which of the following biomolecules has the most diverse functions in the body?

A) carbohydrates
B) proteins
C) nucleic acids
D) lipids
E) These have equally diverse functions.

Question 19

Sickle-cell anemia is caused by

A) an abnormal form of acetylcholine.
B) an abnormal form of iron.
C) too little iron.
D) an abnormal form of hemoglobin.
E) Actually, the cause of this disease is unknown.

Question 20

Which of the following types of proteins defend the body against infectious agents?

A) receptors
B) structural proteins
C) immunoglobulins
D) transport proteins
E) dietary proteins

Question 21

The following amino acid is classified as polar neutral. Which of the following statements best describes why it is classified this way?

A) II only
B) III an IV
C) I and IV
D) I and II
E) III only

Question 22

Which of the following is a complete protein?

A) meat
B) milk
C) eggs
D) soy
E) All of these are complete proteins.

Question 23

The carbon with the asterisk next to it is called the

A) anomeric carbon.
B) alpha carbon.
C) beta carbon.
D) gamma carbon.
E) side chain carbon.

Question 24

The following table lists several common vegetarian foods and the amino acids that they are missing. Which of the following combinations supply a complete protein when consumed together?

A) wheat and corn
B) corn and beans
C) beans and peas
D) peas and corn
E) beans and walnuts

Question 25

At physiological pH, most carboxylic acids exist in their conjugate base form. Which of the following structures illustrates the conjugate base of a carboxylic acid?

A) HCOOH
B) CH₃COO⁺
C) HCOO⁺
D) HCOO ^-
E) CH₃COOH₂⁺

Question 26

How is the following amino acid classified?

A) nonpolar
B) polar neutral
C) polar acidic
D) polar basic
E) None of the above

Question 27

What is the relationship between the following two molecules?

A) They are enantiomers.
B) They are identical.
C) They are conformers.
D) They are constitutional isomers.
E) They are unrelated.

Question 28

The carbon with a smiley face over it is a(n)

A) beta carbon.
B) anomeric carbon.
C) center of chirality.
D) secondary amine.
E) peptide bond.

Question 29

The following amino acid is classified as nonpolar. Which of the following statements best describes why it is classified this way?

A) It does not form a zwitterion.
B) It is neutral at physiological pH.
C) Its side chain is not charged at physiological pH.
D) Its side chain contains only an alkyl group.
E) This amino acid is soluble only in nonpolar solvents.

Question 30

How is the following amino acid classified?

A) nonpolar
B) polar neutral
C) polar acidic
D) polar basic
E) None of the above

Question 31

Aspartic acid has a side chain that contains a carboxylic acid. At physiological pH, what do you expect the structure of aspartic acid to look like?

A)a
B)b
C)c
D)d
E)e

Question 32

Which of the following amino acids is polar neutral?

A)a
B)b
C)c
D)d
E)e

Question 33

What is the relationship between the following two molecules?

A) They are enantiomers.
B) They are identical.
C) They are conformers.
D) They are constitutional isomers.
E) They are unrelated.

Question 34

Which of the amino acids does NOT contain a chiral carbon?

A)a
B)b
C)c
D)d
E)e

Question 35

How is the following amino acid classified?

A) nonpolar
B) polar neutral
C) polar acidic
D) polar basic
E) None of the above

Question 36

What is the charge on lysine, a basic amino acid, at physiological pH?

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

Question 37

Which of the following amino acids contain a thiol?

A) tyrosine
B) histidine
C) threonone
D) cysteine
E) serine

Question 38

Which of the following statements best defines an essential amino acid?

A) It is an amino acid that is necessary for life.
B) It is an amino acid that is synthesized in the body.
C) It is any of the 20 amino acids.
D) It is another name for the nonpolar amino acids.
E) It is an amino acid that cannot be produced by the body.

Question 39

Which of the following amino acid side chains is most often involved in hydrogen bonding?

A) -CH₃
B) -CH₂OH
C) -COOH
D) -CH₂CH₂SCH₃
E) All of the above

Question 40

Amino acids that are not synthesized in the body and must be obtained from the diet are called

A) nonpolar.
B) incomplete.
C) necessary.
D) essential.
E) edible.

Question 41

Is this amino acid L- or D-, and how can you tell?

A) L-, because all amino acids are L.
B) D-, because all amino acids are D.
C) D-, because the amine is on the right.
D) D-, because the amine is on the left.
E) L-, because the amine is on the left.

Question 42

Which of the following is the proper amino acid chain designator of the peptide below? I. Val-Ser-Ala II. Ser-Ala-Val
III) Ala-Ser-Val

A) All of these represent the same molecule.
B) I and III
C) I only
D) II only
E) III only

Question 43

Hydrolysis of the peptide bonds in peptide below would result in

A) no reaction.
B) a single amino acid.
C) two amino acids.
D) three amino acids.
E) four amino acids.

Question 44

In the peptide Ser-Gly-Asp-Ala, the N-terminal amino acid is

A) aspartic acid.
B) alanine.
C) cysteine.
D) serine.
E) glycine.

Question 45

When two amino acids react to form a new amide functional group, the reaction is referred to as a(n)

A) hydrolysis.
B) amidation.
C) esterification.
D) hydration.
E) dehydration.

Question 46

Which of the following statements best describes the naming convention for peptides?

A) There is no naming convention.
B) Start from the C-terminus and continue in order to the N-terminus.
C) Start on the left and continue in order to the right.
D) Start from the N-terminus and continue in order to the C-terminus.
E) Start on the right and continue in order to the left.

Question 47

The boxed bond in the following peptide is a

A) peptide bond.
B) ionic bond.
C) nonpolar covalent bond.
D) hydrogen bond.
E) chiral carbon.

Question 48

Is the peptide shown below chiral?

A) No, molecules with multiple centers of chirality are not chiral.
B) Yes, it has centers of chirality.
C) No, it has no centers of chirality.
D) Yes, it has no centers of chirality.
E) It is not possible to determine whether or not the peptide is chiral.

Question 49

How does your body know which proteins to make and in what order to place the amino acids when the proteins are synthesized?

A) The body does not make proteins; they are consumed in the diet.
B) There are special proteins in which this information is encoded.
C) Our DNA acts as a blueprint for proteins.
D) Our brain does this subconsciously.
E) The answer is not known to science.

Question 50

What is indicated by the arrow pointing to part of the Fischer projection below?

A) Nothing, this is just two molecules with their bonds crossed.
B) This is a carbon in the side chain of an amino acid.
C) This is the alpha carbon of an amino acid.
D) This is a carbon with a planar geometry.
E) This can be any type of atom.

Question 51

What is indicated by the arrow pointing to part of the Fischer projection below?

A) the beta carbon
B) the anomeric carbon
C) a center of chirality
D) a secondary amine
E) a peptide bond

Question 52

When two amino acids react to form a peptide bond, what new functional group is created?

A) an alcohol
B) an amine
C) an amide
D) an ester
E) a phosphoester

Question 53

When several amino acids are connected together, head-to-tail, the resulting molecule is called a(n) __________. When many amino acids are connected together, the molecule is called a(n) ___________.

A) enzyme; polypeptide
B) protein; polypeptide
C) polypeptide; protein
D) polypeptide; enzyme
E) nucleic acid; enzyme

Question 54

Is Gly-Ala-His the same tripeptide as His-Ala-Gly?

A) No, they are constitutional isomers.
B) No, they are stereoisomers.
C) Yes, they are conformers.
D) Yes, they are the same molecule, just flipped over.
E) Yes, the written order of amino acids does not make a difference in the peptide.

Question 55

What is the molecular shape of the carbon with the asterisk next to it?

A) linear
B) bent
C) trigonal planar
D) tetrahedral
E) pyramidal

Question 56

The following compound is a(n)

A) amino acid.
B) dipeptide.
C) tripeptide.
D) polypeptide.
E) protein.

Question 57

Which of the amino acids in the following structure are at the N-terminus?

A) all of them
B) I only
C) III only
D) II and III
E) I and III

Question 58

About how many different proteins are in the human body?

A) one hundred
B) one thousand
C) ten thousand
D) one hundred thousand
E) one million

Question 59

Which of the following structures is the enantiomer of l-alanine?

A)a
B)b
C)c
D)d
E)e

Question 60

What type of bond is a peptide bond?

A) an ionic bond
B) a nonpolar covalent bond
C) a polar covalent bond
D) a hydrogen bond
E) a salt bridge

Question 61

An example of this type of protein is shown below.

A) keratin
B) keratin, elastin, and collagen
C) membrane proteins and globular proteins
D) globular proteins
E) membrane proteins

Question 62

These proteins are structural in nature.

A) keratin
B) keratin, elastin, and collagen
C) membrane proteins and globular proteins
D) globular proteins
E) membrane proteins

Question 63

A protein's native conformation is

A) its shape when it is first made.
B) its shape when it is not bound to a substrate.
C) its three-dimensional shape in which it is biologically active.
D) the shape of the protein without any cofactors.
E) the shape of the protein without any coenzymes.

Question 64

Enzymes are typically composed of this type of protein.

A) keratin
B) keratin, elastin, and collagen
C) membrane proteins and globular proteins
D) globular proteins
E) membrane proteins

Question 65

Which side chain would most likely be found in the interior of a protein, away from the aqueous environment?

A) -CH₂OH
B) -CH₂SH
C) -CH₂COOH
D) -CH₂CONH₂
E)

Question 66

Interleukin-4, a polypeptide, is shown below. In which of the following are the secondary structures labeled correctly?

A) A: random folding B: β-pleated sheets C: α-helix
B) A: β-pleated sheets B: random folding C. α-helix
C) A: random folding B. α-helix C: β-pleated sheets
D) A. α-helix B: random folding C: β-pleated sheets
E) A: β-pleated sheets B: α-helix C: random folding

Question 67

What type of secondary structure is in blue in the following protein?

A) an α-helix
B) a parallel β-pleated sheet
C) an antiparallel β-pleated sheet
D) a random coil
E) This illustration does not show secondary structure.

Question 68

Which of the following correctly shows the electrostatic interaction between amino acids that holds an $\alpha$ -helix or $\beta$ -pleated sheet together?

A)a
B)b
C)c
D)d
E)e

Question 69

In order to break a disulfide bond, what type of reaction occurs?

A) an oxidation
B) a hydration
C) a dehydration
D) a reduction
E) an esterification

Question 70

Sometimes, substitutions of one amino acid for another in a protein results in a large change in secondary and tertiary structure. Sometimes, the substitution leads to very little change. The structure of valine is shown below. Which of the choices of amino acids given would probably cause the least amount of perturbation to protein structure if it was substituted for a valine?

A)a
B)b
C)c
D)d
E)e

Question 71

Which of the following interactions holds the $\alpha$ -helix and the $\beta$ -pleated sheet into its unique folding pattern?

A) covalent bonding between cysteines (-CH₂SH)
B) hydrogen bonding between serines (-CH₂OH)
C) hydrogen bonding between nitrogens and oxygens in the amino acid backbone
D) ionic bonding between acidic and basic amino acid side chains
E) hydrophilic interactions

Question 72

Which side chain would most likely be involved in hydrogen bonding?

A) -CH₂OH
B) -CH₂SH
C) -CH₂COOH
D) -CH₂CONH₂
E)

Question 73

Which of the following amino acids can form a disulfide bridge?

A) glycine
B) alanine
C) serine
D) aspartic acid
E) lysine

Question 74

Which of the following statements best describes a prosthetic group?

A) They are nonpeptide molecules or ions essential to a protein's structure.
B) They are short peptide chains attached to a larger protein.
C) They are nonfunctional components of a protein.
D) They are the active part of a protein.
E) They are the part of the protein that provides structure.

Question 75

Which of the following statements about disulfide bridges is FALSE?

A) Disulfide bridges are found in the tertiary structure of a protein.
B) Disulfide bridges can occur between nonadjacent, and even distant, amino acids.
C) Disulfide bridges are covalent bonds.
D) Reducing a disulfide bridge gives two thiols.
E) A disulfide bridge is weaker than a hydrogen bond.

Question 76

What type of interaction would you expect between the following R groups in the tertiary structure of a protein?

A) hydrogen bonds
B) hydrophobic interactions
C) peptide bonds
D) disulfide bonds
E) salt bridges

Question 77

In some proteins, hydrogen bonding occurs between polar residues and the surrounding aqueous environment, forcing the polar residues to the exterior of the protein. What are the interactions between the polar residues and the aqueous environment called?

A) hydrophilic interactions
B) salt bridges
C) nonpolar interactions
D) hydrophobic interactions
E) dispersion forces

Question 78

What kinds of interactions are NOT part of tertiary protein structure?

A) hydrophobic interactions
B) peptide bonds
C) hydrophilic interactions
D) salt bridges
E) disulfide bonds

Question 79

Which of the following types of interactions result in proteins folding so that nonpolar residues are on the interior of the protein, protected from water?

A) hydrogen bonds
B) salt bridges
C) disulfide bonds
D) hydrophilic interactions
E) dispersion forces

Question 80

Alpha-helices and β-pleated sheets are both examples of

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