Question 1

The P50 value of hemoglobin is higher than normal in all of the following conditions EXCEPT

Accepted Answer

A)   low pH.
B)   high PCO2.
C)   low 2,3-bisphosphoglycerate.
D)   mutant hemoglobin with low oxygen affinity.E) C) and D)
F) A) and D)

Question 2

How do bacterial serine proteases differ from their eukaryotic orthologs?

Accepted Answer

A)   The catalytic triad has different amino acids
B)   They are not inhibited by diisopropylfluorophospate
C)   They are not synthesized as zymogens
D)   They have only one catalytic domain
E)   They show no homology with mammalian serine proteasesF) C) and E)
G) A) and B)

Question 3

The association of O2 with deoxy-myoglobin

Accepted Answer

A)   causes a 60 degree rotation of the porphyrin ring.
B)   is accompanied by the dissociation of 2,3-bisphosphoglycerate.
C)   leads to the reduction of the heme Fe 3+ to Fe 2+.
D)   pulls the iron ion into the plane of the porphyrin ring.
E)   replaces the distal histidine residue in the iron coordination system.F) B) and D)
G) B) and C)

Question 4

How are serine proteases regulated to cleave some peptide bonds more frequently than others?

Accepted Answer

A)   Substrate conformation changes to hide certain cleavage sites on binding to enzyme
B)   Small molecules block some sites
C)   The enzyme dimerizes around the substrate
D)   There is a b-pleated sheet interaction between enzyme and substrate
E)   Zymogen can be activated only at certain sitesF) B) and D)
G) B) and C)

Question 5

In the immunoglobulin G molecule disulfide bonds

Accepted Answer

A)   are located within each immunoglobulin domain.
B)   crosslink antigens to the antigen binding sites.
C)   form between two Met residues.
D)   prevent interactions with cell?surface Fc receptors.E) B) and C)
F) A) and D) A

Question 6

Increased [H+] in blood will most likely

Accepted Answer

A)   increase the pH.
B)   increase the P50 of hemoglobin.
C)   increase the [HCO3-]/[CO2] ratio.
D)   increase the oxygen affinity of hemoglobin.
E)   decrease buffering by hemoglobin.F) A) and E)
G) B) and E)

Question 7

Generation of antibody diversity is primarily caused by

Accepted Answer

A)   Covalent modification of immunoglobulin proteins.
B)   Differences in splicing of the primary RNA transcripts of antibody genes.
C)   Rearrangement of DNA.
D)   DNA recombination in response to particular antigens.
E)   Specific folding of antibody-combining sites induced by particular antigens.F) B) and E)
G) A) and B)

Question 8

All of the following statements regarding the transport of carbon dioxide and molecular oxygen by hemoglobin are true EXCEPT

Accepted Answer

A)   the isohydric shift is possible because deoxygenated hemoglobin is a stronger base than oxygenated hemoglobin.
B)   if the tissues are using glucose only as a fuel, then the isohydric shift plus some other buffering effect of blood is necessary to prevent the pH of plasma from changing very much.
C)   erythrocytes in venous blood have a lower concentration of chloride ion than when they are in the arterial system.
D)   the total bicarbonate concentration in venous blood is higher than in arterial blood.
E)   the PO2 and pH in venous blood tend to be lower than in arterial blood.F) A) and C)
G) All of the above

Question 9

The AB-sites (antigen reactive sites)  are located on which of the following portions of the immunoglobulin chains?

Accepted Answer

A)   VL + CH
B)   VL + CL
C)   VL + FC
D)   VL + VH
E)   VH + CLF) A) and C)
G) B) and C)

Question 10

Which of the following is a characteristic of hemoglobin?

Accepted Answer

A)   It is composed of four identical polypeptide chains.
B)   There is one heme group per active Hb molecule.
C)   Oxygen and carbon dioxide compete for the same binding site on heme.
D)   It is an elongated, fibrous-type protein, hence is not very soluble in water.
E)   Binding of oxygen to Hb results in change in the pKa of certain histidine residues toward lower values.F) B) and D)
G) B) and C)

Question 11

The complementarity-determining regions (CDR)  of human immunoglobulin G

Accepted Answer

A)   are common to the general structure of all immunoglobulin domains.
B)   consist of short segments of highly variable amino acid sequence.
C)   form covalent complexes with antigens.
D)   have been identified only on the light chain polypeptides.
E)   participate in the binding of these proteins to cell surface receptors.F) All of the above
G) A) and E)

Question 12

The combining site for antigen is formed by the

Accepted Answer

A)   constant regions of the heavy chains.
B)   constant regions of the light chains.
C)   variable region of the light chain and the constant region of the heavy chain.
D)   variable region of the light chain and the variable region of the heavy chain.E) All of the above
F) A) and D)

Question 13

All of the following are true of IgM antibodies, EXCEPT which one?

Accepted Answer

A)   They fix complement.
B)   They occur on the surface of B-lymphocytes.
C)   They predominate in the primary immune response to antigen.
D)   They are glycoproteins.
E)   They are a molecule with a single, defined amino acid sequence.F) D) and E)
G) All of the above

Question 14

Which of the following statements about the interaction of heme units of hemoproteins with oxygen is correct?

Accepted Answer

A)   Binding of 2,3-bisphosphoglycerate (BPG)  to hemoglobin leads to increased binding of oxygen.
B)   Binding of oxygen to one myoglobin increases the strength of binding of oxygen to other myoglobins.
C)   In blood of peripheral tissues, the loss of an oxygen by a heme unit is balanced stoichiometrically by the loss of one hydrogen.
D)   The binding of oxygen by separated beta-chains of hemoglobin is described by a sigmoid curve.
E)   As oxygen binds to hemoglobin, the pKa's of certain amino acid sidechains decrease.F) None of the above
G) A) and E) E

Question 15

One principal function of complement is to

Accepted Answer

A)   inactivate perforins.
B)   mediate the release of histamine.
C)   bind antibodies attached to cell surfaces and to lyse these cells.
D)   phagocytize antigen.
E)   cross-link allergens.F) A) and B)
G) A) and E)

Question 16

Which statement about 2,3-bisphosphoglycerate is TRUE?

Accepted Answer

A)   It is a high-energy compound which can support the phosphorylation of ADP to ATP in glycolysis.
B)   It is formed by the ATP-dependent phosphorylation of 3-phosphoglycerate.
C)   It is important as an intermediate in the formation of 1,3-bisphosphoglycerate from glucose.
D)   It is converted to 3-phosphoglycerate by the action of a phosphatase.
E)   It is formed by the oxidative phosphorylation of glyceraldehyde 3-phosphate.F) D) and E)
G) A) and D)

Question 17

Which of the following is TRUE of Fc receptors for immunoglobulins?

Accepted Answer

A)   They are found on cells of the reticuloendothelial system and are involved in antibody-dependent, cell-mediated cytotoxicity.
B)   They are associated with the T3 complex of the T-cell receptor.
C)   They are not able to bind immunoglobulin.
D)   They are receptors which recognize the Fab portion of the antibody.
E)   They are all unique, because each has a specific antigen binding capacity.F) A) and E)
G) All of the above

Question 18

The fact that when a deoxyhemoglobin crystal is oxygenated it breaks up into fragments supports the statement that

Accepted Answer

A)   hemoglobin is a tetramer.
B)   oxyhemoglobin and deoxyhemoglobin have different conformations.
C)   each subunit of hemoglobin has identical oxygen-binding sites.
D)   all subunits of a hemoglobin molecule must have the same conformation at any given time.
E)   each oxygen-binding site of hemoglobin is on a separate subunit.F) A) and E)
G) B) and D)

Question 19

Which one of the following conditions promotes association of oxygen with hemoglobin?

Accepted Answer

A)   Low PO2.
B)   Low PCO2.
C)   Low pH.
D)   High 2,3 diphosphoglycerate.
E)   High total CO2 content.F) B) and C)
G) None of the above

Question 20

In the typical globin protein, the conserved proximal histidine residue participates in the

Accepted Answer

A)   binding of a proton as an allosteric effector.
B)   coordination of the iron component of heme.
C)   discrimination in binding between O2 and CO.
D)   reversible formation of a carbamate.E) A) and D)
F) B) and C) B

Exam 9: Protein II: Structure-Function Relationships in Protein Families

The P50 value of hemoglobin is higher than normal in all of the following conditions EXCEPT

Correct AnswerverifiedShow Answer

How do bacterial serine proteases differ from their eukaryotic orthologs?

Correct AnswerverifiedShow Answer

The association of O2 with deoxy-myoglobin

Correct AnswerverifiedShow Answer

How are serine proteases regulated to cleave some peptide bonds more frequently than others?

Correct AnswerverifiedShow Answer

In the immunoglobulin G molecule disulfide bonds

Correct AnswerverifiedA

Increased [H+] in blood will most likely

Correct AnswerverifiedShow Answer

Generation of antibody diversity is primarily caused by

Correct AnswerverifiedShow Answer

All of the following statements regarding the transport of carbon dioxide and molecular oxygen by hemoglobin are true EXCEPT

Correct AnswerverifiedShow Answer

The AB-sites (antigen reactive sites) are located on which of the following portions of the immunoglobulin chains?

Correct AnswerverifiedShow Answer

Which of the following is a characteristic of hemoglobin?

Correct AnswerverifiedShow Answer

The complementarity-determining regions (CDR) of human immunoglobulin G

Correct AnswerverifiedShow Answer

The combining site for antigen is formed by the

Correct AnswerverifiedShow Answer

All of the following are true of IgM antibodies, EXCEPT which one?

Correct AnswerverifiedShow Answer

Which of the following statements about the interaction of heme units of hemoproteins with oxygen is correct?

Correct AnswerverifiedE

One principal function of complement is to

Correct AnswerverifiedShow Answer

Which statement about 2,3-bisphosphoglycerate is TRUE?

Correct AnswerverifiedShow Answer

Which of the following is TRUE of Fc receptors for immunoglobulins?

Correct AnswerverifiedShow Answer

The fact that when a deoxyhemoglobin crystal is oxygenated it breaks up into fragments supports the statement that

Correct AnswerverifiedShow Answer

Which one of the following conditions promotes association of oxygen with hemoglobin?

Correct AnswerverifiedShow Answer

In the typical globin protein, the conserved proximal histidine residue participates in the

Correct AnswerverifiedB

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The association of O₂ with deoxy-myoglobin

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A

Increased [H⁺] in blood will most likely

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E

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B