Exam Prep Proteins Structure and Function Ch.13 Guinn

Test questions for Chapter 13

Proteins: Structure and Function

1. Sickle-cell anemia is caused by
   1. an abnormal form of acetylcholine.
   2. an abnormal form of iron.
   3. too little iron.
   4. an abnormal form of hemoglobin.
   5. Actually, the cause of this disease is unknown.
2. Which of the following choices is NOT a problem associated with sickle-cell anemia?
   1. People with sickle-cell anemia are prone to severe headaches.
   2. People with sickle-cell anemia are prone to episodes of infection.
   3. Organs can be damaged because of sickled red blood cells.
   4. Sickle-cell anemia can cause anemia.
   5. The sickle cells can aggregate and clog blood vessels.
3. What percentage of amino acids in sickle cell hemoglobin is different from normal hemoglobin?
   1. 100%
   2. 50%
   3. 25%
   4. 10%
   5. <1%
4. Which of the following is NOT one of the four categories of biomolecules?
   1. proteins
   2. vitamins
   3. lipids
   4. carbohydrates
   5. nucleic acids
5. Which of the following biomolecules has the most diverse functions in the body?
   1. carbohydrates
   2. proteins
   3. nucleic acids
   4. lipids
   5. These have equally diverse functions.
6. Which of the following types of proteins defend the body against infectious agents?
7. receptors
8. structural proteins
9. immunoglobulins
10. transport proteins
11. dietary proteins

1. Which of the following types of proteins provides physical support to tissues?
   1. receptors
   2. structural proteins
   3. immunoglobulins
   4. transport proteins
   5. dietary proteins

1. Hemoglobin is an example of this type of protein.
   1. receptors
   2. structural proteins
   3. immunoglobulins
   4. transport proteins
   5. dietary proteins

1. Which type of protein can be used for energy when necessary?
   1. receptors
   2. structural proteins
   3. immunoglobulins
   4. transport proteins
   5. dietary proteins

1. Which type of protein signals cellular events?
   1. receptors
   2. structural proteins
   3. immunoglobulins
   4. transport proteins
   5. dietary proteins
2. Which of the following choices are the best labels for this amino acid?

• 1. 1: amino acid 2: carbon 3: side chain 4: alcohol
  2. 1: amide 2: α-carbon 3: R 4. ester
  3. 1: amine 2: side chain 3: α-carbon 4. ester
  4. 1: amide 2: α-carbon 3: side chain 4. carbonyl
  5. 1: amine 2: α-carbon 3: side chain 4. carboxylic acid

1. How many naturally occurring amino acids are there?
   1. 1
   2. 5
   3. 10
   4. 20
   5. hundreds
2. An amino acid zwitterion has
   1. a net positive charge.
   2. a net negative charge.
   3. a net neutral charge.
   4. any non-neutral charge.
   5. Zwitterions can have any charge.
3. Physiological pH is a pH of approximately
   1. 5.7.
   2. 7.3.
   3. 8.1.
   4. 9.1.
   5. 0.
4. Which of the following structures illustrates an amino acid as a zwitterion?

a. b. c. d. e.

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

a. b. c. d. e.

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

a. b. c. d. e.

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

a. b. c. d. e.

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

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

a. b. c. d. e.

1. 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?
   1. HCOOH
   2. CH₃COO⁺
   3. HCOO⁺
   4. HCOO⁻
   5. CH₃COOH₂⁺
2. 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. b. c. d. e.

1. What is the charge on lysine, a basic amino acid, at physiological pH?
   1. +2
   2. +1
   3. 0
   4. −1
   5. −2
2. Which of the following amino acids is polar neutral?

a. b. c. d. e.

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

• 1. It does not form a zwitterion.
  2. It is neutral at physiological pH.
  3. Its side chain is not charged at physiological pH.
  4. Its side chain contains only an alkyl group.
  5. This amino acid is soluble only in nonpolar solvents.

1. 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

• 1. III only
  2. III an IV
  3. I and IV
  4. I and II

1. Which of the following amino acid side chains is most often involved in hydrogen bonding?
   1. –CH₃
   2. –CH₂OH
   3. –COOH
   4. –CH₂CH₂SCH₃
   5. All of the above
2. How is the following amino acid classified?

1. nonpolar
2. polar neutral
3. polar acidic
4. polar basic
5. None of the above
6. How is the following amino acid classified?

1. nonpolar
2. polar neutral
3. polar acidic
4. polar basic
5. None of the above
6. How is the following amino acid classified?

• 1. nonpolar
  2. polar neutral
  3. polar acidic
  4. polar basic
  5. None of the above

1. Which of the following amino acids contain a thiol?
   1. tyrosine
   2. histidine
   3. threonone
   4. cysteine
   5. serine
2. Which of the following statements best defines an essential amino acid?
   1. It is an amino acid that is necessary for life.
   2. It is an amino acid that is synthesized in the body.
   3. It is any of the 20 amino acids.
   4. It is another name for the nonpolar amino acids.
   5. It is an amino acid that cannot be produced by the body.
3. 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?

• 1. wheat and corn
  2. corn and beans
  3. beans and peas
  4. peas and corn
  5. beans and walnuts

1. Amino acids that are not synthesized in the body and must be obtained from the diet are called
   1. nonpolar.
   2. incomplete.
   3. necessary.
   4. essential.
   5. edible.
2. Which of the following is a complete protein?
   1. meat
   2. milk
   3. eggs
   4. soy
   5. All of these are complete proteins.
3. Which of the amino acids does NOT contain a chiral carbon?

a. b. c. d. e.

1. What is the relationship between the following two molecules?

• 1. They are enantiomers.
  2. They are identical.
  3. They are conformers.
  4. They are constitutional isomers.
  5. They are unrelated.

1. What is the relationship between the following two molecules?

• 1. They are enantiomers.
  2. They are identical.
  3. They are conformers.
  4. They are constitutional isomers.
  5. They are unrelated.

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

• 1. beta carbon.
  2. anomeric carbon.
  3. center of chirality.
  4. secondary amine.
  5. peptide bond.

1. The carbon with the asterisk next to it is called the

• 1. anomeric carbon.
  2. alpha carbon.
  3. beta carbon.
  4. gamma carbon.
  5. side chain carbon.

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

• 1. linear
  2. bent
  3. trigonal planar
  4. tetrahedral
  5. pyramidal

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

• 1. Nothing, this is just two molecules with their bonds crossed.
  2. This is a carbon in the side chain of an amino acid.
  3. This is the alpha carbon of an amino acid.
  4. This is a carbon with a planar geometry.
  5. This can be any type of atom.

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

• 1. the beta carbon
  2. the anomeric carbon
  3. a center of chirality
  4. a secondary amine
  5. a peptide bond

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

a. b. c. d. e.

1. Is this amino acid l- or d-, and how can you tell?

1. l-, because all amino acids are l.
2. d-, because all amino acids are d.
3. d-, because the amine is on the right.
4. d-, because the amine is on the left.
5. l-, because the amine is on the left.
6. 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) ___________.
7. enzyme; polypeptide
8. protein; polypeptide
9. polypeptide; protein
10. polypeptide; enzyme
11. nucleic acid; enzyme
12. The following compound is a(n)

• 1. amino acid.
  2. dipeptide.
  3. tripeptide.
  4. polypeptide.
  5. protein.

1. The boxed bond in the following peptide is a

1. peptide bond.
2. ionic bond.
3. nonpolar covalent bond.
4. hydrogen bond.
5. chiral carbon.
6. Hydrolysis of the peptide bonds in peptide below would result in

1. no reaction.
2. a single amino acid.
3. two amino acids.
4. three amino acids.
5. four amino acids.
6. Which of the following is the proper amino acid chain designator of the peptide below?

• • • 1. Val-Ser-Ala
      2. Ser-Ala-Val
      3. Ala-Ser-Val

1. All of these represent the same molecule.
2. I and III
3. I only
4. II only
5. III only
6. When two amino acids react to form a new amide functional group, the reaction is referred to as a(n)
   1. hydrolysis.
   2. amidation.
   3. esterification.
   4. hydration.
   5. dehydration.
7. What type of bond is a peptide bond?
8. an ionic bond
9. a nonpolar covalent bond
10. a polar covalent bond
11. a hydrogen bond
12. a salt bridge
13. When two amino acids react to form a peptide bond, what new functional group is created?
14. an alcohol
15. an amine
16. an amide
17. an ester
18. a phosphoester
19. Is Gly-Ala-His the same tripeptide as His-Ala-Gly?
20. No, they are constitutional isomers.
21. No, they are stereoisomers.
22. Yes, they are conformers.
23. Yes, they are the same molecule, just flipped over.
24. Yes, the written order of amino acids does not make a difference in the peptide.
25. Which of the following statements best describes the naming convention for peptides?
26. There is no naming convention.
27. Start from the C-terminus and continue in order to the N-terminus.
28. Start on the left and continue in order to the right.
29. Start from the N-terminus and continue in order to the C-terminus.
30. Start on the right and continue in order to the left.
31. Which of the amino acids in the following structure are at the N-terminus?

I II III

1. all of them
2. I only
3. III only
4. II and III
5. I and III
6. In the peptide Ser-Gly-Asp-Ala, the N-terminal amino acid is
7. aspartic acid.
8. alanine.
9. cysteine.
10. serine.
11. glycine.
12. Is the peptide shown below chiral?

1. No, molecules with multiple centers of chirality are not chiral.
2. Yes, it has centers of chirality.
3. No, it has no centers of chirality.
4. Yes, it has no centers of chirality.
5. It is not possible to determine whether or not the peptide is chiral.
6. About how many different proteins are in the human body?
7. one hundred
8. one thousand
9. ten thousand
10. one hundred thousand
11. one million
12. How does your body know which proteins to make and in what order to place the amino acids when the proteins are synthesized?
13. The body does not make proteins; they are consumed in the diet.
14. There are special proteins in which this information is encoded.
15. Our DNA acts as a blueprint for proteins.
16. Our brain does this subconsciously.
17. The answer is not known to science.
18. Enzymes are typically composed of this type of protein.
19. keratin
20. keratin, elastin, and collagen
21. membrane proteins and globular proteins
22. globular proteins
23. membrane proteins
24. These proteins are structural in nature.
25. keratin
26. keratin, elastin, and collagen
27. membrane proteins and globular proteins
28. globular proteins
29. membrane proteins
30. An example of this type of protein is shown below.

1. keratin
2. keratin, elastin, and collagen
3. membrane proteins and globular proteins
4. globular proteins
5. membrane proteins
6. A protein’s native conformation is
7. its shape when it is first made.
8. its shape when it is not bound to a substrate.
9. its three-dimensional shape in which it is biologically active.
10. the shape of the protein without any cofactors.
11. the shape of the protein without any coenzymes.
12. 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. b. c. d. e.

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

Image from the RCSB PDB (www.rcsb.org) of PDB ID 1ITL (Smith, L.J., Redfield, C., Boyd, J., Lawrence, G.M., Edwards, R.G., Smith, R.A., Dobson, C.M. (1992) Human interleukin 4. The solution structure of a four-helix bundle protein. J.Mol.Biol. 224: 899-904).

C

A

B

1. A: random folding B: β-pleated sheets C: α-helix
2. A: β-pleated sheets B: random folding C. α-helix
3. A: random folding B. α-helix C: β-pleated sheets
4. A. α-helix B: random folding C: β-pleated sheets
5. A: β-pleated sheets B: α-helix C: random folding
6. Alpha-helices and β-pleated sheets are both examples of
7. primary structure.
8. secondary structure.
9. tertiary structure.
10. quaternary structure.
11. both secondary and tertiary structure.
12. Which of the following interactions holds the α-helix and the β-pleated sheet into its unique folding pattern?
13. covalent bonding between cysteines (–CH₂SH)
14. hydrogen bonding between serines (–CH₂OH)
15. hydrogen bonding between nitrogens and oxygens in the amino acid backbone
16. ionic bonding between acidic and basic amino acid side chains
17. hydrophilic interactions
18. Which of the following correctly shows the electrostatic interaction between amino acids that holds an α-helix or β-pleated sheet together?

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

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

and

1. hydrogen bonds
2. hydrophobic interactions
3. peptide bonds
4. disulfide bonds
5. salt bridges
6. What kinds of interactions are NOT part of tertiary protein structure?
7. hydrophobic interactions
8. peptide bonds
9. hydrophilic interactions
10. salt bridges
11. disulfide bonds
12. Which side chain would most likely be found in the interior of a protein, away from the aqueous environment?
13. –CH₂OH
14. –CH₂SH
15. –CH₂COOH
16. –CH₂CONH₂
17. 
18. Which side chain would most likely be involved in hydrogen bonding?
19. –CH₂OH
20. –CH₂SH
21. –CH₂COOH
22. –CH₂CONH₂
23. 
24. Which of the following amino acids can form a disulfide bridge?
25. glycine
26. alanine
27. serine
28. aspartic acid
29. lysine
30. Which of the following statements about disulfide bridges is FALSE?
31. Disulfide bridges are found in the tertiary structure of a protein.
32. Disulfide bridges can occur between nonadjacent, and even distant, amino acids.
33. Disulfide bridges are covalent bonds.
34. Reducing a disulfide bridge gives two thiols.
35. A disulfide bridge is weaker than a hydrogen bond.
36. In order to break a disulfide bond, what type of reaction occurs?
    1. an oxidation
    2. a hydration
    3. a dehydration
    4. a reduction
    5. an esterification
37. 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?
38. hydrophilic interactions
39. salt bridges
40. nonpolar interactions
41. hydrophobic interactions
42. dispersion forces
43. 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?
44. hydrogen bonds
45. salt bridges
46. disulfide bonds
47. hydrophilic interactions
48. dispersion forces
49. Which of the following statements best describes a prosthetic group?
50. They are nonpeptide molecules or ions essential to a protein’s structure.
51. They are short peptide chains attached to a larger protein.
52. They are nonfunctional components of a protein.
53. They are the active part of a protein.
54. They are the part of the protein that provides structure.
55. How does the potential energy of a correctly folded protein compare to the energy of an unfolded protein or a wrongly folded one?
    1. The energy of a correctly folded protein is lower.
    2. The energy of a correctly folded protein is higher.
    3. The energy of proteins is the same no matter how they are folded or unfolded.
    4. Proteins do not have energy.
    5. Sometimes the energy of a correctly folded protein is lower and sometimes it is higher.
56. Which of the following statements about quaternary structure is TRUE?
57. Quaternary structure is the position of subunits in the overall structure of a protein.
58. All proteins have quaternary structure.
59. Quaternary structure is unaffected by acids or heat.
60. Quaternary structure is determined by the same interaction that holds an α-helix together.
61. Quaternary structure is how prosthetic groups are held in a protein.
62. The structure of myoglobin is shown below. Myoglobin contains which of the following components?

A

B

C

Image from the RCSB PDB (www.rcsb.org) of PDB ID 1FCS (Rizzi, M., Bolognesi, M., Coda, A., Cutruzzola, F., Allocatelli, C.T., Brancaccio, A., Brunori, M. (1993) Crystal structure of a distal site double mutant of sperm whale myoglobin at 1.6 A resolution. FEBS Lett. 320: 13-16).

α-helices

β-pleated sheets

a prosthetic group

1. I only
2. II only
3. III only
4. I and II
5. I and III
6. The structure of myoglobin is shown below. Which level of architecture does this protein lack?

Image from the RCSB PDB (www.rcsb.org) of PDB ID 1FCS (Rizzi, M., Bolognesi, M., Coda, A., Cutruzzola, F., Allocatelli, C.T., Brancaccio, A., Brunori, M. (1993) Crystal structure of a distal site double mutant of sperm whale myoglobin at 1.6 A resolution. FEBS Lett. 320: 13-16).

A

B

C

1. This protein has all levels of architecture.
2. primary
3. secondary
4. tertiary
5. quaternary
6. The most common motifs for this level of structure are the helix and the β- pleated sheet.
   1. primary structure
   2. secondary structure
   3. tertiary structure
   4. quaternary structure
   5. both secondary and tertiary
7. The amino acid sequence is the ________ of a protein.
   1. primary structure
   2. secondary structure
   3. tertiary structure
   4. quaternary structure
   5. both secondary and tertiary

1. Not all proteins have this level of protein architecture.
   1. primary structure
   2. secondary structure
   3. tertiary structure
   4. quaternary structure
   5. both secondary and tertiary
2. This is a regular folding pattern in localized regions of the polypeptide backbone.
   1. primary structure
   2. secondary structure
   3. tertiary structure
   4. quaternary structure
   5. both secondary and tertiary
3. The following is a description of an enzyme called superoxide dismutase. Refer to this paragraph to answer the following question.

Superoxide dismutase is an enzyme that detoxifies a free radical called superoxide. This radical is responsible for causing injury during reperfusion after a heart attack, and is also thought to play a role in Parkinson’s Disease.^a Depending on what organism the protein is found in, it occurs either as a dimer or tetramer of identical subunits.^b The subunits are mostly α-helical with some β-sheet near the C-terminus.^c A metal binding site for manganese, iron, nickel or copper/zinc is composed of residues from both the N-terminus and the C-terminus.^d These residues are: His-26, His-81, Asp-167, His-171.^e

Which statement refers to quaternary structure?

a. a b. b c. c d. d e. e

1. The following is a description of an enzyme called superoxide dismutase. Refer to this paragraph to answer the following question.

Superoxide dismutase is an enzyme that detoxifies a free radical called superoxide. This radical is responsible for causing injury during reperfusion after a heart attack, and is also thought to play a role in Parkinson’s Disease.^a Depending on what organism the protein is found in, it occurs either as a dimer or tetramer of identical subunits.^b The subunits are mostly α-helical with some β-sheet near the C-terminus.^c A metal binding site for manganese, iron, nickel or copper/zinc is composed of residues from both the N-terminus and the C-terminus.^d These residues are: His-26, His-81, Asp-167, His-171.^e

Which statement refers to secondary structure?

a. a b. b c. c d. d e. e

1. The following is a description of an enzyme called superoxide dismutase. Refer to this paragraph to answer the following question.

Superoxide dismutase is an enzyme that detoxifies a free radical called superoxide. This radical is responsible for causing injury during reperfusion after a heart attack, and is also thought to play a role in Parkinson’s Disease.^a Depending on what organism the protein is found in, it occurs either as a dimer or tetramer of identical subunits.^b The subunits are mostly α-helical with some β-sheet near the C-terminus.^c A metal binding site for manganese, iron, nickel or copper/zinc is composed of residues from both the N-terminus and the C-terminus.^d These residues are: His-26, His-81, Asp-167, His-171.^e

Which statement refers to primary structure?

a. a b. b c. c d. d e. e

1. The following is a description of an enzyme called superoxide dismutase. Refer to this paragraph to answer the following question.

Superoxide dismutase is an enzyme that detoxifies a free radical called superoxide. This radical is responsible for causing injury during reperfusion after a heart attack, and is also thought to play a role in Parkinson’s Disease.^a Depending on what organism the protein is found in, it occurs either as a dimer or tetramer of identical subunits.^b The subunits are mostly α-helical with some β-sheet near the C-terminus.^c A metal binding site for manganese, iron, nickel or copper/zinc is composed of residues from both the N-terminus and the C-terminus.^d These residues are: His-26, His-81, Asp-167, His-171.^e

Which statement refers to a prosthetic group?

a. a b. b c. c d. d e. e

1. Which of the following levels of architecture are not affected by denaturation?
   1. primary
   2. secondary
   3. tertiary
   4. quaternary
   5. All levels of architecture are affected by denaturation.
2. Why doesn’t denaturation affect the primary structure of a protein?
3. Actually, denaturation does hydrolyze amino acids.
4. because peptide bonds are higher energy bonds than other interactions
5. because peptide bonds are stronger than other interactions
6. because peptide bonds are weaker than other interactions
7. because peptide bonds cannot be broken under any circumstances
8. Which of the following are methods of denaturing a protein?
9. pH changes
10. heating
11. mechanical agitation
12. detergents
13. All of the above
14. Which of the following occur when a protein is denatured?
    • 1. Covalent bonds are broken.
      2. Hydrogen bonds are broken.
      3. The protein loses its shape.
      4. The protein loses its biological activity.
15. All of these are true statements.
16. All of these statements, except IV, are true.
17. All of these statements, except I, are true.
18. Only II and III are true.
19. None of these statements is true.
20. During alkalosis of a protein, shown below, salt bridges are broken, resulting in denaturation. Which choice shows the products of alkalosis?

1. During acidosis of a protein, shown below, salt bridges are broken, resulting in denaturation. Which choice shows the products of alkalosis?

1. The purpose of an enzyme is to
2. be structural in nature.
3. transport key molecules.
4. defend the body against infectious agents.
5. catalyze chemical reactions.
6. All of these are purposes of enzymes.
7. Which of the following statements best describes the function of an enzyme in the body?
8. An enzyme acts as a buffer.
9. An enzyme transports waste out of the blood.
10. An enzyme signals cellular events.
11. An enzyme catalyzes chemical reactions.
12. All of the above
13. What types of biomolecules are enzymes?
    1. only proteins
    2. only DNA molecules
    3. proteins and some carbohydrates
    4. proteins and some RNA molecules
    5. carbohydrates and some RNA molecules
14. In an enzyme catalyzed reaction, the reactant that the enzyme acts upon is called the
15. prosthetic group,
16. substrate,
17. coenzyme,
18. reagent,
19. cofactor,
20. Which of the following statements best describes the purpose of a catalyst in a chemical reaction?
21. The purpose of a catalyst is to speed up the rate of the reaction.
22. The purpose of a catalyst is to lower the energy of the reactants.
23. The purpose of a catalyst is to slow down the rate of the reaction.
24. The purpose of a catalyst is to lower the energy of the products.
25. The purpose of a catalyst is to increase the activation energy of the reaction.
26. Which of the following statements about enzyme names is FALSE?
27. Enzymes are often named after the type of reaction that they catalyze or their substrate.
28. Enzyme names almost always include the name of any cofactors involved in their reaction.
29. Enzyme names often have -ase at the end of them.
30. Some enzymes are named after where they were isolated from.
31. Enzyme names are typically italicized.
32. A protein acts as a catalyst if its name ends with
33. -ase.
34. -ate.
35. -ine.
36. -ous.
37. -ite.
38. Which statement best describes how an enzyme lowers the activation energy of a reaction?
39. The enzyme covalently binds to the substrate, lowering its energy.
40. The enzyme chemically reacts with the substrate to make it more reactive.
41. The enzyme increases the temperature of the substrate, making it more reactive.
42. The substrate is held in the correct orientation for reaction to occur.
43. All of the above
44. Which of the following statements best describes the induced-fit model of enzyme action?
45. In this model, the enzyme changes the shape of a substrate using a cofactor.
46. In this model, the enzyme adjusts it shape to adapt to the shape of the substrate.
47. In this model, the enzyme induces a change of polarity in the substrate that results in bonding.
48. In this model, the enzyme’s active site is complementary to the shape of the substrate.
49. In this model, the enzyme’s active site chemically reacts with the substrate.
50. Hemoglobin contains iron. The iron is an example of a(n)
51. cofactor.
52. heme.
53. enzyme.
54. coenzyme.
55. metal.
56. The pH for optimum activity for most enzymes is
57. 5.4.
58. 7.4.
59. 8.0.
60. 9.0.
61. 10.4.
62. According to the following graph of activity as a function of pH, at which of the following pHs is the reaction that pepsin catalyzes the fastest?

1. 1.0
2. 2.0
3. 5.0
4. 7.0
5. 11
6. Below is a graph of enzyme activity as a function of pH. Given the information on this graph, where is pepsin most likely to be found?

1. stomach (pH 2)
2. liver (pH 5)
3. pancreas (pH 7)
4. blood (pH 7.4)
5. small intestine (pH 8)
6. Assuming that the enzyme represented by the graph below is found in humans, what temperature is most likely to be the optimum temperature?

1. 0ºC
2. 10ºC
3. 37ºC
4. 55ºC
5. 100ºC
6. According to the graph below, which of the following is TRUE?

1. At high temperature, the activity of the enzyme decreases more sharply than it does at low temperature.
2. At low temperature, the activity of the enzyme decreases more sharply than it does at high temperature.
3. The maximum activity is at the lowest temperature.
4. The maximum activity is at the highest temperature.
5. The activity of the enzyme is the same at all temperatures.
6. According to the following graph, the activity of the enzyme decreases more sharply at high temperature than at low temperature. What are the reasons for this observation?

1. As temperature is increased, the substrate binding slowly becomes poorer.
2. As temperature is decreased, the enzyme moves more slowly and so reacts more slowly.
3. At higher temperatures, the enzyme is denatured and stops working entirely.
4. Temperature has no effect on enzyme activity.
   1. I only
   2. IV only
   3. I and III
   4. II and III
   5. All are correct.
5. An enzyme inhibitor is a compound that
6. prevents a substrate from binding to the enzyme.
7. deforms enzymes.
8. binds to the active site of an enzyme.
9. prevents an enzyme from functioning.
10. can do all of the above.
11. Select the statement that best described a key difference between competitive and noncompetitive inhibitors.
12. A competitive inhibitor binds to the active site and a noncompetitive inhibitor does not.
13. A noncompetitive inhibitor binds to the active site and a competitive inhibitor does not.
14. A competitive inhibitor is more effective than a noncompetitive inhibitor.
15. A noncompetitive inhibitor is more effective than a competitive inhibitor.
16. A noncompetitive inhibitor has structural similarities to the enzyme’s active site and the competitive inhibitor does not.
17. Inflammation and pain caused by injury results from the production of molecules called prostaglandins. Aspirin and other anti-inflammatories work by binding to the active site of an enzyme that produces the prostaglandins, thus preventing their synthesis. What type of molecule is aspirin?
18. a cofactor
19. a substrate
20. a competitive inhibitor
21. a noncompetitive inhibitor
22. a coenzyme
23. Tamoxifen is a drug used to prevent recurrence of certain types of breast cancers that require estrogen to grow. Tamoxifen binds to the active site of the estrogen receptor protein, preventing estrogen from binding to the enzyme. Once Tamoxifen binds to the protein, the protein is permanently deactivated. Which of the following descriptions best fits Tamoxifen?
24. Tamoxifen is an irreversible, noncompetitive inhibitor.
25. Tamoxifen is a reversible, noncompetitive inhibitor.
26. Tamoxifen is an irreversible, competitive inhibitor.
27. Tamoxifen is a reversible, competitive inhibitor.
28. Tamoxifen is not an inhibitor.
29. Acetylcholine is a neurotransmitter that initiates muscle contraction. In order for muscle to relax after contraction, acetylcholine must be broken down into choline and acetate by the enzyme acetylcholinesterase. Nerve agents such as Sarin inhibit acetylcholinesterase by permanently covalently bonding to a serine amino acid in the active site of the enzyme, causing muscle paralysis. What type of inhibitor is Sarin?
    1. a competitive reversible inhibitor
    2. a noncompetitive reversible inhibitor
    3. a competitive irreversible inhibitor
    4. a noncompetitive irreversible inhibitor
    5. Sarin is not an inhibitor.
30. Which of the following statements about noncompetitive inhibitors is FALSE?
31. Noncompetitive inhibitors are sometimes involved in feedback inhibition.
32. Noncompetitive inhibitors can serve a regulatory role in the body.
33. Noncompetitive inhibitors do not bind to the active site of an enzyme.
34. Increasing the concentration of a substrate restores function of an enzyme in the presence of a noncompetitive inhibitor.
35. Binding of a noncompetitive inhibitor results in deformation of an enzyme’s active site.
36. Which of the following statements best describes the strategy used for treating hypertension through drug therapies?
37. The strategy is to suppress how the body detects sodium.
38. The strategy is to suppress how the body detects low blood pressure.
39. The strategy is to lower blood pressure directly.
40. The strategy is to permanently disable renin.
41. The strategy is to inhibit the pathway that the body uses to increase blood pressure.
42. The structure of one of the first ACE inhibitors is given below. What is the purpose of the sulfur in this molecule?

1. It is highly reactive with angiotensin II.
2. It binds to a metal on the exterior of ACE.
3. It holds the molecule in the active site of ACE.
4. It makes Captopril into a strong acid.
5. It forms a covalent bond with ACE, permanently deactivating it.