Biochemistry Concepts And Connections 1st Edition By Appling – Test Bank

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Biochemistry Concepts And Connections 1st Edition By Appling – Test Bank

Biochemistry: Concepts and Connections (Appling et al.)

Chapter 6   The Three-Dimensional Structure of Proteins

 

1) In considering protein secondary structure which of the following is INCORRECT?

  1. A) An α helix repeats after 18 residues and has 3.6 residues per turn.
  2. B) A network of main-chain hydrogen bonds connect β strands in a β sheet.
  3. C) The most common structures are the α helix and the β sheet.
  4. D) The 310helix is right-handed and often contains proline residues.
  5. E) The β strands can be in either parallel or antiparallel configuration.

Answer:  D

Objective:  6.1

Global LO:  G2

 

2) The amino acid side chain residues in an α helix point outwards away from the center of the helix.

Answer:  TRUE

Objective:  6.1

Global LO:  G2

 

3) ________ between amide protons and carbonyl oxygens is necessary to stabilize a regular folding of protein secondary structure.

Answer:  Hydrogen bonding

Objective:  6.1

Global LO:  G7

 

4) A ________ plot describes which structures in a polypeptide are sterically possible and which are not based on the angles of rotation about the backbone Namide —Cα and Cα-Ccarbonyl bonds.

Answer:  Ramachandran

Objective:  6.3

Global LO:  G9

 

5) Which of the following statements about α-keratins is FALSE?

  1. A) They include a major class of protein that comprises hair, fingernails and animal skin.
  2. B) Individual molecules are α-helical.
  3. C) There is a strip of contiguous hydrophobic surface making a shallow spiral around the helix.
  4. D) They include a small globular regions covalently linked to the surface.
  5. E) Pairs of α-helices twist about each other in a coiled-coil structure held together entirely by hydrophobic interactions.

Answer:  E

Objective:  6.4

Global LO:  G7

 

6) The protein that makes up about a third of the total protein mass in animals is:

  1. A) β-keratin.
  2. B) collagen.
  3. C) hemoglobin.
  4. D) myoglobin.
  5. E) α-keratin.

Answer:  B

Objective:  6.4

Global LO:  G7

 

7) Fibroin is a β-sheet protein, with a high proportion of glycine.

Answer:  TRUE

Objective:  6.4

Global LO:  G7

 

8) Tropocollagen is a double helix of two left-handed polypeptide chains.

Answer:  FALSE

Objective:  6.4

Global LO:  G7

 

9) Scurvy results in weakness in collagen fibres because the enzymes that catalyze ________ of proline and lysine residues in collagen require Vitamin C.

Answer:  hydroxylation

Objective:  6.4

Global LO:  G7

 

10) Which of the following is CORRECT when considering the tertiary structure of globular proteins?

  1. A) β sheets are usually twisted or wrapped into barrel structures.
  2. B) Hydrophobic residues are normally on the inside and hydrophilic residues are on the outside.
  3. C) The amino acid proline never occurs in a region where the polypeptide chain bends or turns.
  4. D) All parts of the proteins can be classified as helix, β sheet or turns.
  5. E) None of the above.

Answer:  B

Objective:  6.6

Global LO:  G7

 

11) Proteins cannot self-assemble into a functional conformation after they have been denatured.

Answer:  FALSE

Objective:  6.6

Global LO:  G2

 

12) Protein folding is a random process, whereby a vast number of possible conformations are tested to find the desired most stable state.

Answer:  FALSE

Objective:  6.7

Global LO:  G2

13) The folded conformation of proteins can be stabilized by the binding of a metal ion or cofactor.

Answer:  TRUE

Objective:  6.9

Global LO:  G7

 

14) The interactions that stabilize multisubunit complexes are different to those that stabilize tertiary structure.

Answer:  FALSE

Objective:  6.9

Global LO:  G7

 

15) Protein folding is a thermodynamically favorable process under physiological conditions because:

  1. A) there is an increase in entropy associated with protein folding.
  2. B) there is a decrease in entropy of the solvent by burying hydrophobic groups within the molecule.
  3. C) of the large negative enthalpy change associated with many noncovalent interactions.
  4. D) no intermediate stage disulphide bonds form during the folding process.
  5. E) all of the above.

Answer:  C

Objective:  6.10

Global LO:  G7

 

16) The cavity in the GroEL-GroES complex from E. coli provides a favorable environment that prevents ________ and mis-folding.

Answer:  aggregation

Objective:  6.11

Global LO:  G7

 

17) Bovine spongiform encephalopathy is an infectious disease caused by a prion protein, which undergoes a ________ change to become pathogenic.

Answer:  conformational

Objective:  6.12

Global LO:  G7

 

18) Proteins have an asymmetrical tertiary structure, while multisubunit proteins can exhibit several types of symmetry.

Answer:  TRUE

Objective:  6.14

Global LO:  G7

 

19) The functional organization of proteins where specific complexes of two or more polypeptides are formed is called ________ structure.

Answer:  quaternary

Objective:  6.14

Global LO:  G7

20) Which technique is able to investigate secondary structural features of proteins?

  1. A) Infrared spectroscopy
  2. B) Ultraviolet spectroscopy
  3. C) Fluorescence spectroscopy
  4. D) Circular dichroism
  5. E) All of the above

Answer:  E

Objective:  6.15

Global LO:  G9

 

21) ________ spectroscopy can be used to study dynamic processes in solution.

Answer:  Nuclear magnetic resonance

Objective:  6.15

Global LO:  G9

 

22) SDS gel electrophoresis can be used to determine:

  1. A) whether subunits in a protein complex are identical or not.
  2. B) the molecular mass of a native protein complex.
  3. C) the overall charge on a polypeptide.
  4. D) the molecular mass of denatured protein subunits.
  5. E) none of the above.

Answer:  D

Objective:  6.18

Global LO:  G9

 

Biochemistry: Concepts and Connections (Appling et al.)

Chapter 7   Protein Function and Evolution

 

1) Which of the following is NOT true of immunoglobulin molecules?

  1. A) They consist of four polypeptide chains held together by disulphide bridges.
  2. B) They have two identical heavy chains and two identical light chains.
  3. C) Antigenic determinants reside only in the variable region of the light chains.
  4. D) Proteolytic cleavage can generate fragments containing the antigen-binding site.
  5. E) Some are membrane bound.

Answer:  C

Objective:  7.3

Global LO:  G2

 

2) The immunoglobulin domain is a stable scaffold containing two antiparallel β- sheets upon which to display hypervariable loops.

Answer:  TRUE

Objective:  7.3

Global LO:  G7

 

3) The specific interaction between an antibody and antigen occurs by virtue of both shape and ________ complementarity.

Answer:  charge

Objective:  7.4

Global LO:  G7

 

4) Which of the following statements is FALSE?

  1. A) Myoglobin is a single polypeptide chain folded about a heme prosthetic group.
  2. B) Hemoglobin is a tetramer, each of which binds a heme group.
  3. C) In both hemoglobin and myoglobin, iron is chelated by a tetrapyrole ring system.
  4. D) The iron in both hemoglobin and myoglobin has two coordination sites that bind to oxygen.
  5. E) Hydrogen bonding to a histidine residue assists stabilization of the Fe2+-O2complex in both hemoglobin and myoglobin.

Answer:  D

Objective:  7.9

Global LO:  G2

 

5) Both myoglobin and hemoglobin exhibit cooperative binding to oxygen.

Answer:  FALSE

Objective:  7.9

Global LO:  G2

 

6) The conserved residues in the hemoglobins and myoglobins include the ________ proximal and distal to the heme iron.

Answer:  histidines

Objective:  7.9

Global LO:  G7

7) The ________ binding of oxygen to hemoglobin is facilitated by changes in protein conformation upon oxygen binding to one subunit that affect the binding of oxygen to another subunit.

Answer:  cooperative

Objective:  7.12

Global LO:  G2

 

8) Which of the following observations helps to explain the conformational changes that occur in hemoglobin upon binding to oxygen?

  1. A) The four heme groups are positioned close to the surface of the molecule.
  2. B) An αβ dimer rotates and slides with respect to the other dimer upon binding oxygen.
  3. C) Neither the heme nor the iron ion in the deoxy conformation is in a planar conformation.
  4. D) All of the above
  5. E) B and C

Answer:  E

Objective:  7.14

Global LO:  G2

 

9) Fetal hemoglobin has a higher affinity for oxygen than does maternal hemoglobin because it has a higher affinity for the allosteric regulator 2,3-bisphosphoglycerate.

Answer:  FALSE

Objective:  7.16

Global LO:  G7

 

10) The production of carbon dioxide during respiration in aerobic tissues lowers the pH in erythrocytes, which in turn ________ the affinity of oxygen binding to hemoglobin.

Answer:  decreases

Objective:  7.18

Global LO:  G2

 

11) Comparison of globin sequences from many different species suggests that myoglobin and hemoglobin have evolved from a single myoglobin-like protein.

Answer:  TRUE

Objective:  7.21

Global LO:  G7

 

12) The sickle cell mutation causes oxyhemoglobin molecules to ________ due to hydrophobic interactions because a glutamate residue is replaced with a valine.

Answer:  aggregate

Objective:  7.22

Global LO:  G7

 

 

13) Which of the following statements about muscle contraction is TRUE?

  1. A) ATP hydrolysis releases myosin from actin.
  2. B) ATP hydrolysis results in strong binding of myosin to actin.
  3. C) ATP hydrolysis causes a conformational change in the myosin head.
  4. D) Muscle contraction occurs as ATP is hydrolyzed.
  5. E) ATP hydrolysis must occur before the actin-binding site closes.

Answer:  C

Objective:  7.23

Global LO:  G7

14) The heavy chain of the muscle form of myosin:

  1. A) forms a coiled-coil structure with a globular head domain.
  2. B) contains the motor domain within the C-terminal region.
  3. C) is a complex of 540 kDa.
  4. D) binds ATP near the C-termini.
  5. E) has two covalently bound light chains.

Answer:  A

Objective:  7.24

Global LO:  G7

 

15) F-actin is a polymer of G-actin monomers and exhibits symmetry.

Answer:  FALSE

Objective:  7.24

Global LO:  G7

 

16) The A band of skeletal muscle is formed by noncovalent cross-bridges between the thin filaments that are mainly ________ and the thick filaments that are mainly ________.

Answer:  actin, myosin

Objective:  7.25

Global LO:  G7

 

17) The most critical substance in stimulating muscle contraction is:

  1. A) ATP.
  2. B) Ca2+.
  3. C) tropomyosin.
  4. D) troponin C.
  5. E) troponin T.

Answer:  B

Objective:  7.27

Global LO:  G7

 

 

18) Calcium regulates muscle contraction by binding to:

  1. A) actin.
  2. B) myosin.
  3. C) tropomyosin.
  4. D) troponin C.
  5. E) troponin T.

Answer:  D

Objective:  7.27

Global LO:  G7

 

19) The greatest conformational change in the neck piece of myosin occurs during ATP hydrolysis.

Answer:  FALSE

Objective:  7.27

Global LO:  G7

 

20) The concentration of Ca2+ in the myoplasm can increase as much as 10,000 fold in response to a motor nerve impulse.

Answer:  TRUE

Objective:  7.27

Global LO:  G7

21) Antibodies cannot be used to purify proteins because the antibody-antigen interaction is too strong.

Answer:  FALSE

Objective:  7.28

Global LO:  G9

 

22) Enzyme-linked immunosorbent assay, western blotting and immunofluorescent light microscopy all make use of the specific interaction between an antigen and an ________.

Answer:  antibody

Objective:  7.28

Global LO:  G9