Test 1

Question 1

What is formed when carbon dioxide reacts with the amino terminal group of deoxyhemoglobin?

Answer 1

Carbamate

Question 2

Which of the following is a genetic disease that results from a decreased production of one of the subunits of hemoglobin?

Answer 2

Thalassemia

Question 3

What is the organic portion of the heme group in hemoglobin?

Answer 3

Protoporphyrin

Question 4

A __________________ inhibitor often has a structure similar to the substrate and often reversibly binds to the active site of the enzyme but can be displaced by substrate.

Answer 4

Competitive

Question 5

What is the common strategy by which catalysis occurs?
a) increasing the probability of product formation
b) shifting the reaction equilibrium
c) stabilization of transition state
d) all of the above
e) none of the above

Answer 5

c) stabilization of transition state

Question 6

enzyme catalysts can be
a) RNA.
b) lipids.
c) proteins.
d) a and c.
e) none of the above.

Answer 6

d) a and c

Question 7

Examples of cofactors include

a) Zn+2, Mg+2, and Ni+2.
b) biotin and thiamine pyrophosphate.
c) pyridoxal phosphate and coenzyme A.
d) b and c.
e) a, b, and c.

Answer 7

e) a, b, and c.

Question 8

Which of the following is not true?

a) Enzymes force reactions to proceed in only one direction.
b) Enzymes alter the equilibrium of the reaction.
c) Enzymes alter the standard free energy of the reaction.
d) All of the above are true.
e) None of the above are true.

Answer 8

e) None of the above are true

Question 9

Proteins are often made of regions that can fold and function as an independent entity from the whole protein. These regions are called:
a. complementary
b. oligomers
c. peptides
d. sites
e. domains

Answer 9

e. domains

Question 10

Which of the following statements is false?
a. Disulfide linkages are important for higher order keratin structure, as in hair.
b. Gly residues are particularly abundant in collagen.
c. Collagen is a protein in which the polypeptides are mainly in the α(alpha) helix conformation.
d. Silk is made of a protein in which the polypeptide is almost entirely in the β sheet conformation.
e. α(alpha) is a protein in which the polypeptides are mainly in the α(alpha) helix conformation.

Answer 10

c. Collagen is a protein in which the polypeptides are mainly in the α(alpha) helix conformation.

Question 11

Planarity of the peptide bond means that no rotation occurs about the ______ bond while rotation is allowed at the ______ and ______ bonds of the polypeptide backbone.
a. C(O)-N; Cα-Cβ; N-Cα
b. N-Cα; Cα- C(O); C(O)-N
c. Cα-C(O); C(O)-N; N-Cα
d. C(O)-N; Cα-C(O); N-Cα
e. none of the above

Answer 11

d. C(O)-N; Cα-C(O); N-Cα

Question 12

Tertiary structure is defined as:
a. the folding of a single polypeptide chain in 3D space.
b. the sequence of amino acids.
c. hydrogen bonding interactions between adjacent amino acid residues into helical or pleated segments.
d. the way in which separate folded monomeric proteins subunits associate to form oligomeric.
e. all are true.

Answer 12

a. the folding of a single polypeptide chain in 3D space.

Question 13

Which two amino acids contain a sulfur atom?
a. cysteine and methionine
b. serine and methionine
c. cysteine and threonine
d. methionine and threonine
e. serine and threonine

Answer 13

a. cysteine and methionine

Question 14

Which amino acid forms disulfide bonds?
a. cysteine
b. histidine
c. methionine
d. proline
e. serine

Answer 14

a. cysteine

Question 15

One method used to prevent disulfide bond interference with protein sequencing procedure is:
a. cleaving proteins with proteases that specifically recognize disulfide bonds.
b. reducing disulfide bridges and preventing their re-formation by further modifying the -SH groups.
c. protecting the disulfide bridge against spontaneous reduction.
d. removing cysteines from protein sequences by proteolytic.
e. sequencing proteins that do not contain cysteine residues.

Answer 15

b. reducing disulfide bridges and preventing their re-formation by further modifying the -SH groups.

Question 16

Which of the following is not correct concerning myoglobin?
A) The heme group is bound to the globin chain by two disulfide bonds to cysteine residues.
B) The diameter of the iron ion decreases upon binding to oxygen.
C) The iron of the heme group is in the Fe+2 oxidation state.
D) The function of myoglobin is oxygen storage in muscle.
E) The globin chain contains an extensive α-helix structure.

Answer 16

A) The heme group is bound to the globin chain by two disulfide bonds to cysteine residues.

Question 17

Which of the following is correct concerning the differences between hemoglobin and myoglobin?
A. Both hemoglobin and myoglobin are tetrameric proteins.
B. Hemoglobin exhibits a hyperbolic O2 saturation curve while myoglobin exhibits a sigmoid shaped curve.
C. All of these options.
D. Hemoglobin exhibits cooperative binding of O2 while myoglobin does not.
E. Hemoglobin exhibits a higher degree of O2 saturation at all physiologically relevant partial pressures of O2 than does myoglobin.

Answer 17

D. Hemoglobin exhibits cooperative binding of O2 while myoglobin does not.

Question 18

Why is the peptide bond planar?
a. Bulky side chains prevent free rotation around the bond.
b. Hydrogen bonding between the NH and C=O groups limits movement.
c. It contains partial double-bond character, preventing rotation.
d. All of the answers are correct.
e. None of the answers are correct.

Answer 18

c. It contains partial double-bond character, preventing rotation.

Question 19

The term “quaternary” with respect to protein structure means
a. a repeating structure stabilized by intrachain hydrogen bonds.
b. a multisubunit structure
c. the ability to form all four kinds of noncovalent bonds.
d. a linear sequence of four amino acids.
e. None of the answers is correct.

Answer 19

b. a multisubunit structure

Question 20

SDS gel electrophoresis (SDS PAGE) can be used to determine:
a. whether subunits in a protein complex are identical or not.
b. the molecular mass of a denatured protein subunits.
c. the molecular mass of a native protein complex.
d. the overall charge on polypeptide.
e. none of the above.

Answer 20

b. the molecular mass of a denatured protein subunits.

Question 21

The formation of a peptide bond between two amino acids is an example of a(n) _______________ reaction.
a. cleavage
b. phosphorylation
c. isomerization
d. condensation
e. ionization

Answer 21

d. condensation

Question 22

How many amino acids are there in one turn of an α(alpha) helix?
a. 1
b. 2.8
c. 4.2
d. 3.6
e. 10

Answer 22

d. 3.6

Question 23

The major reason that antiparallel β-stranded sheets are most stable than the parallel β-stranded sheets is that the sheets made of parallel β-strands:
a. have weaker hydrogen bonds between adjacent strands.
b. are in slightly less extended configuration than antiparallel strands.
c. do not have as many disulfide crosslinks between adjacent strands.
d. do not stack in sheets as well as antiparallel strands.
e. have fewer lateral hydrogen bonds than antiparallel.

Answer 23

a. have weaker hydrogen bonds between adjacent strands.

Question 24

Two proteins are similar in size but differ significantly in the number of acidic and basic amino acids. Which of the following techniques would be best suited to separating these two proteins?
a. gel-filtration chromatography
b. ion-exchange chromatography
c. SDS PAGE
d. affinity chromatography
e. none of the above.

Answer 24

b. ion-exchange chromatography

Question 25

__________ amino acids are almost never found in the interior of a protein, but the protein surface may consist of ____________ amino acids.
a. Nonpolar; both polar and nonpolar
b. Nonpolar; mostly nonpolar
c. Polar; only polar
d. Polar, both polar and nonpolar
e. Polar; only nonpolar

Answer 25

d. Polar, both polar and nonpolar

Question 26

Which of the following statements is correct for hemoglobin and oxygen transport?
a. The oxygen binds to the proximal histidine residue of the globin chain.
b. Bonding of carbon dioxide to hemoglobin molecules increases the binding of oxygen.
c. Hemoglobin binds more oxygen as the pH is lowered.
d. The binding of each O2 molecule to hemoglobin increases its affinity for the next O2.
e. Hemoglobin binds more oxygen at higher [BPG] concentrations.

Answer 26

d. The binding of each O2 molecule to hemoglobin increases its affinity for the next O2.