Question 1

Which of the following is NOT a difference between the T form (tense or taut form)of deoxyhemoglobin and the oxyhemoglobin (the R form or relaxed form)?

Accepted Answer

A) covalent linkages between subunits 
B) specific intrachain hydrogen bonds 
C) salt links (ion-pair bonds)between ?-subunits 
D) interchain salt bridges 
A) covalent linkages between subunits 
B) specific intrachain hydrogen bonds 
C) salt links (ion-pair bonds)between ?-subunits 
D) interchain salt bridges A

Question 2

Which of the following is NOT a characteristic of allosteric enzymes?

Accepted Answer

A) Effectors may show stimulatory or inhibitory activity. 
B) They have multiple subunits. 
C) They obey Michaelis-Menten kinetics. 
D) Binding of 1 subunit impacts binding of substrate to other subunits. 
A) Effectors may show stimulatory or inhibitory activity. 
B) They have multiple subunits. 
C) They obey Michaelis-Menten kinetics. 
D) Binding of 1 subunit impacts binding of substrate to other subunits. C

Question 3

Which of the following is the mechanism by which proinsulin is converted into insulin?

Accepted Answer

A) by proteolytic excision of a specific peptide 
B) by allosteric binding of glucose 
C) by phosphorylation to the active form 
D) by removal of phosphate by converter enzymes 
A) by proteolytic excision of a specific peptide 
B) by allosteric binding of glucose 
C) by phosphorylation to the active form 
D) by removal of phosphate by converter enzymes A

Question 4

Which of the following terms is used to define the process that occurs when binding 1 equivalent of S to an allosteric protein enhances the binding of additional equivalents of S to the same protein molecule?

Accepted Answer

A) negative heterotropic effect 
B) positive homotropic effect 
C) positive heterotropic effect 
D) negative homotropic effect 
A) negative heterotropic effect 
B) positive homotropic effect 
C) positive heterotropic effect 
D) negative homotropic effect

Question 5

Which of the following regarding the differences between Hb and Mb is NOT correct?

Accepted Answer

A) Hb shows sigmoidal,whereas Mb shows hyperbolic oxygen saturation curves. 
B) Hb shows cooperativity,whereas Mb does not. 
C) Hb binds O₂ more tightly than Mb. 
D) Hb-oxygen binding is dependent on physiological changes in pH,whereas Mb-oxygen binding is not. 
A) Hb shows sigmoidal,whereas Mb shows hyperbolic oxygen saturation curves. 
B) Hb shows cooperativity,whereas Mb does not. 
C) Hb binds O₂ more tightly than Mb. 
D) Hb-oxygen binding is dependent on physiological changes in pH,whereas Mb-oxygen binding is not.

Question 6

Which of the following mechanisms describes the function of pyruvate dehydrogenase?

Accepted Answer

A) to convert glucose-1-phosphate to glucose-6-phosphate 
B) to inhibit the production of glucose-1-phosphate 
C) to catalyze the conversion of glyceraldehyde into pyruvate 
D) to stimulate the breakdown of glycogen 
A) to convert glucose-1-phosphate to glucose-6-phosphate 
B) to inhibit the production of glucose-1-phosphate 
C) to catalyze the conversion of glyceraldehyde into pyruvate 
D) to stimulate the breakdown of glycogen

Question 7

Which of the following effects does the presence of a negative allosteric effector have on an allosteric protein?

Accepted Answer

A) causes a shift to the left in the sigmoidal curve 
B) increases the number of R conformations 
C) decreases the cooperativity of the substrate 
D) raises the apparent value of the equilibrium constant,L 
A) causes a shift to the left in the sigmoidal curve 
B) increases the number of R conformations 
C) decreases the cooperativity of the substrate 
D) raises the apparent value of the equilibrium constant,L

Question 8

Which of the following terms describes the regulation of metabolism by activation of the gene encoding a particular enzyme?

Accepted Answer

A) covalent modification 
B) repression 
C) induction 
D) allosteric activation 
A) covalent modification 
B) repression 
C) induction 
D) allosteric activation

Question 9

Why are we are protected to some extent against low level CO poisoning?

Accepted Answer

A) His F8 on Hb distorts the heme iron atom out of the heme plane and attracts O₂,but not CO. 
B) Affinity of Hb for O₂ is much greater than for CO. 
C) His E7 blocks perpendicular binding of CO to heme iron,allowing for better binding competition by O₂. 
D) The competition of O₂ for heme is much greater than CO for heme. 
A) His F8 on Hb distorts the heme iron atom out of the heme plane and attracts O₂,but not CO. 
B) Affinity of Hb for O₂ is much greater than for CO. 
C) His E7 blocks perpendicular binding of CO to heme iron,allowing for better binding competition by O₂. 
D) The competition of O₂ for heme is much greater than CO for heme.

Question 10

Which of the following conditions causes cell sickling in sickle cell anemia?

Accepted Answer

A) interaction of oxyHb S with the cell membrane 
B) precipitation of deoxyHb S into long,chain-like fibres 
C) formation of oxyHb S complexes and subsequent cell disruption 
D) precipitation of Hb S-Hb A hybrid molecules 
A) interaction of oxyHb S with the cell membrane 
B) precipitation of deoxyHb S into long,chain-like fibres 
C) formation of oxyHb S complexes and subsequent cell disruption 
D) precipitation of Hb S-Hb A hybrid molecules

Question 11

Which of the following statements regarding isozymes is correct?

Accepted Answer

A) They catalyze the same reaction but have vastly different structures. 
B) They are always monomeric proteins. 
C) Their differences are based upon the type of metal ions needed for catalysis. 
D) They often respond to different inhibitors and activators. 
A) They catalyze the same reaction but have vastly different structures. 
B) They are always monomeric proteins. 
C) Their differences are based upon the type of metal ions needed for catalysis. 
D) They often respond to different inhibitors and activators.

Question 12

For the MWC model,the half-maximum velocity changes in response to effectors.Which of the following explains the reason for this?

Accepted Answer

A) Vmax remains constant because the [S] is not rate limiting. 
B) Vmax changes because the [S] is saturating. 
C) Vmax remains constant because the [S] is rate limiting. 
D) Vmax changes because the [S] is not saturating. 
A) Vmax remains constant because the [S] is not rate limiting. 
B) Vmax changes because the [S] is saturating. 
C) Vmax remains constant because the [S] is rate limiting. 
D) Vmax changes because the [S] is not saturating.

Question 13

Which of the following regarding the isozymes of lactate dehydrogenase,which are present in a number of different tissues is correct?

Accepted Answer

A) They have similar Km values for lactate. 
B) They have different kinetic parameters. 
C) The amount of subunit phosphorylation differs. 
D) The ratios of A and B subunits are similar in the different tissues. 
A) They have similar Km values for lactate. 
B) They have different kinetic parameters. 
C) The amount of subunit phosphorylation differs. 
D) The ratios of A and B subunits are similar in the different tissues.

Question 14

Which of the following components of the eukaryotic PDH complex has the largest number of subunits?

Accepted Answer

A) lipoate 
B) E2 
C) TPP 
D) E3 
A) lipoate 
B) E2 
C) TPP 
D) E3

Question 15

Which of the following is the reason why BPG shifts the oxygen saturation curve of Hb to the right?

Accepted Answer

A) BPG binds to deoxyHb and unloads O₂ at tissues. 
B) BPG binds to oxyHb and unloads O₂ at tissues. 
C) BPG binds to deoxyHb and unloads O₂ at the lungs. 
D) BPG binds to oxyHb and unloads O₂ at the lungs. 
A) BPG binds to deoxyHb and unloads O₂ at tissues. 
B) BPG binds to oxyHb and unloads O₂ at tissues. 
C) BPG binds to deoxyHb and unloads O₂ at the lungs. 
D) BPG binds to oxyHb and unloads O₂ at the lungs.

Question 16

Which of the following molecules activates PDH kinase?

Accepted Answer

A) ADP 
B) calcium 
C) NADH 
D) insulin 
A) ADP 
B) calcium 
C) NADH 
D) insulin

Question 17

Which of the following mechanisms is the quickest method of influencing an enzymatic activity?

Accepted Answer

A) allosteric regulation 
B) covalent modification 
C) enzyme induction 
D) activation of a zymogen 
A) allosteric regulation 
B) covalent modification 
C) enzyme induction 
D) activation of a zymogen

Question 18

Which of the following is a feature of an enzyme that displays negative cooperativity?

Accepted Answer

A) Enzyme activity is increased when [S] >>> than the value of K0.5. 
B) Enzyme activity is increased when [S] 0.5. 
C) Enzyme activity is decreased when [S] 0.5. 
D) Enzyme activity is unchanged when [S] >>> than the value of K0.5 
A) Enzyme activity is increased when [S] >>> than the value of K0.5. 
B) Enzyme activity is increased when [S] 0.5. 
C) Enzyme activity is decreased when [S] 0.5. 
D) Enzyme activity is unchanged when [S] >>> than the value of K0.5

Question 19

Which of the following regarding the effect of protons on binding of O₂ by hemoglobin is NOT correct?

Accepted Answer

A) The saturation curve of Hb for O₂ is displaced to the left (greater binding)as acidity increases. 
B) Actively metabolizing tissues produce acid,which is an antagonist of oxygen binding by Hb. 
C) As pH decreases,dissociation of O₂ from Hb is enhanced. 
D) The phenomenon is called the Bohr effect. 
A) The saturation curve of Hb for O₂ is displaced to the left (greater binding)as acidity increases. 
B) Actively metabolizing tissues produce acid,which is an antagonist of oxygen binding by Hb. 
C) As pH decreases,dissociation of O₂ from Hb is enhanced. 
D) The phenomenon is called the Bohr effect.

Question 20

Which of the following amino acid residues of the PDH complex is the target of phosphorylation?

Accepted Answer

A) serine of E1 
B) tyrosine of E1 
C) serine of E2 
D) tyrosine of E2 
A) serine of E1 
B) tyrosine of E1 
C) serine of E2 
D) tyrosine of E2

Exam 14: Enzyme Regulation

Which of the following is NOT a difference between the T form (tense or taut form)of deoxyhemoglobin and the oxyhemoglobin (the R form or relaxed form)?

Which of the following is NOT a characteristic of allosteric enzymes?

Which of the following is the mechanism by which proinsulin is converted into insulin?

Which of the following terms is used to define the process that occurs when binding 1 equivalent of S to an allosteric protein enhances the binding of additional equivalents of S to the same protein molecule?

Which of the following regarding the differences between Hb and Mb is NOT correct?

Which of the following mechanisms describes the function of pyruvate dehydrogenase?

Which of the following effects does the presence of a negative allosteric effector have on an allosteric protein?

Which of the following terms describes the regulation of metabolism by activation of the gene encoding a particular enzyme?

Why are we are protected to some extent against low level CO poisoning?

Which of the following conditions causes cell sickling in sickle cell anemia?

Which of the following statements regarding isozymes is correct?

For the MWC model,the half-maximum velocity changes in response to effectors.Which of the following explains the reason for this?

Which of the following regarding the isozymes of lactate dehydrogenase,which are present in a number of different tissues is correct?

Which of the following components of the eukaryotic PDH complex has the largest number of subunits?

Which of the following is the reason why BPG shifts the oxygen saturation curve of Hb to the right?

Which of the following molecules activates PDH kinase?

Which of the following mechanisms is the quickest method of influencing an enzymatic activity?

Which of the following is a feature of an enzyme that displays negative cooperativity?

Which of the following regarding the effect of protons on binding of O₂ by hemoglobin is NOT correct?

Which of the following amino acid residues of the PDH complex is the target of phosphorylation?

The Facts of Life: Chemistry Is the Logic of Biological Phenomena

Water: the Medium of Life

Thermodynamics of Biological Systems

Amino Acids

Proteins: Their Primary Structure and Biological Functions

Proteins: Secondary, tertiary, and Quaternary Structure

Carbohydrates and the Glycoconjugates of Cell Surfaces

Lipids

Lipid Biosynthesis

Membranes and Membrane Transport

The Reception and Transmission of Extracellular Information

Enzymes Kinetics and Specificity

Mechanisms of Enzyme Action

Molecular Motors

Nutrition and the Organization of Metabolism

Glycolysis

The Tricarboxylic Acid Cycle

Electron Transport and Oxidative Phosphorylation

Photosynthesis

Gluconeogenesis, glycogen Metabolism, and the Pentose Phosphate Pathway

Fatty Acid Catabolism

Nitrogen Acquisition and Amino Acid Metabolism

Nucleotides and Nucleic Acids

Structure of Nucleic Acids

Synthesis and Degradation of Nucleotides

Recombinant Dna: Cloning and Creation of Chimeric Genes

DNA Metabolism: Replication, recombination, and Repair

Transcription and the Regulation of Gene Expression

Protein Synthesis

Post-Transcriptional Regulation of Gene Expression

Completing the Protein Life Cycle: Folding, processing, and Degradation

Metabolic Integration and Organ Specialization

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