Extra Notes for the Final

Question 1

Quaternary structure refers to the non-covalent interaction(s) between polymeric units, such as two or more monomer protein units that noncovalently interact. Which of the following scenarios for nucleic acids most closely resembles quaternary structure?
A) self-assembly of RNA-protein subunits in the tobacco mosaic virus

B) interaction of DNA with proteins during replication

C) RNA and protein association in ribosomes

D) All of the above

E) None of the above

Answer 1

D) All of the above

Question 2

RNA molecules can form secondary structures (double stranded regions) if there are complementary bases in the right positions. Which of the following RNA strands would be most likely to form a specific secondary region?
A) 5’-AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA-3’

B) 5’-UUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUUU-3’

C) 5’-GGGAUUUUUUUUUUUUUUUUAAAAAAAAAAAAAAAAUCCC-3’

D) 5’-UGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUGUG-3’

E) 5’-GGAAAAGGAGAUGGGCAAGGGGAAAAGGAGAUGGGCAAGG-3’

Answer 2

C) 5’-GGGAUUUUUUUUUUUUUUUUAAAAAAAAAAAAAAAAUCCC-3’

Question 3

Which of the following characteristics is associated with the B form of DNA?

A) the sugars are located in the interior of the double helix

B) the distance between base pairs along the axis of the helix is 0.8 nm (8 Å)

C) the major and minor grooves are readily apparent

D) the planes of the bases make about a 20° angle with the helix axis

E) None of the above

Answer 3

C) the major and minor grooves are readily apparent

Question 4

In your research on DNA structure, you find a double stranded molecule that is located in GC-rich regions of chromosomes, has alternating purine-pyrimidine sequences, is left handed, has 13.6 base-pairs (bp) per turn, a diameter of 1.8 nm (18 Å), displays a deep minor groove, and an outer convex surface that is analogous to a major groove. You found DNA in the ___ conformation.

A) A

B) B

C) P

D) S

E) Z

Answer 4

E) Z

Question 5

A friend tells you that only four different kinds of bases are found in RNA. You disagree and your friend asks you to provide at least one reason for your answer. A reason you can pose is:

A) RNA contains only the nucleotides C, G, T, and U.

B) In some RNAs, uridine is methylated to thymidine.

C) RNA contains only the nucelotides A, C, G, and U.

D) RNA is unstable, and thus has variable nucleotide composition.

E) All of the above

Answer 5

B) In some RNAs, uridine is methylated to thymidine.

Question 6

Which of the following statements is true?

A) Prokaryotic DNA is normally complexed with histone octamers forming nucleosomes.

B) Bacterial ribosomes consist of 40S and 60S subunits.

C) Eukaryotic ribosomes have a sedimentation coefficient of 80S.

D) In eukaryotic cells, replication, transcription, and translation take place in the nucleus.

E) All of the above

Answer 6

C) Eukaryotic ribosomes have a sedimentation coefficient of 80S.

Question 7

Which type of topoisomerase can untwist the DNA double helix?

A) Type I only

B) Type II only

C) Both types I and II

D) Topoisomerases cannot untwist the DNA double helix

E) What are topoisomerases?

Answer 7

C) Both types I and II

Question 8

What is the advantage for DNA from having thymine and not uracil?

A) The replacement of uracil with thymine allows the replication machinery to differentiate between DNA and RNA.

B) Cytosine can spontaneously deaminate to uracil, thus the extra methyl on thymine serves as a quality control check.

C) There is no particular benefit from the T to U replacement in DNA compared to RNA.

D) The extra methyl group on thymine as compared to uracil is key to the formation of the double-stranded DNA helix.

E) An extra hydrogen bond can be formed with A by using T instead of U

Answer 8

B) Cytosine can spontaneously deaminate to uracil, thus the extra methyl on thymine serves as a quality control check.

Question 9

Why does double-stranded DNA (dsDNA) with a high A-T content have a lower transition temperature, Tm, than double-stranded DNA with a high C-G content?

A) A-T-rich dsDNA requires more energy to separate into single strands than G-C rich dsDNA.

B) Purine bases are more susceptible to hydrolysis at high temperature than are pyrimidine bases.

C) Elevated temperature breaks the backbone bonds between C and G bases less easily than they break the backbone bonds between A and T bases.

D) G-C-rich dsDNA requires more energy to separate into single strands than A-T rich dsDNA.

E) A-T-rich dsDNA does not form propeller twists in dsDNA whereas G-C does.

Answer 9

D) G-C-rich dsDNA requires more energy to separate into single strands than A-T rich dsDNA.

Question 10

Which of the following statement regarding replication forks is correct?

A) At a replication fork, two strands of dsDNA are separated, and a new DNA strand forms on each separate strand.

B) A replication fork is the site of formation of new RNA.

C) In bacteria, each origin of replication is associated with a single replication fork.

D) A replication fork is the site on DNA at which RNA polymerase acts.

E) Replication forks are formed by the DNA.

Answer 10

A) At a replication fork, two strands of dsDNA are separated, and a new DNA strand forms on each separate strand.

Question 11

DNA synthesis always takes place from the 5’ to the 3’ end. The template strands from dsDNA are aligned in opposite directions from each other. How does nature deal with this situation?

A) A second type of DNA polymerase is used to synthesize DNA from the 3’ to the 5’ end.

B) The 3’-to-5’ template strand is synthesized in small chunks that are then ligated together.

C) Okazaki fragments are synthesized on the 5’-to-3’ template strand and then ligated together.

D) The 5’-to-3’ template strand wraps around in a trombone fashion so that the DNA polymerase can move along it in the 3’-to-5’ direction, replicating the strand continuously.

E) Mother Nature does not deal with these menial issues.

Answer 11

C) Okazaki fragments are synthesized on the 5’-to-3’ template strand and then ligated together.

Question 12

How do the DNA polymerases of eukaryotes differ from those of prokaryotes?

A) Prokaryotic DNA polymerases usually do not have exonuclease activity, in contrast to DNA polymerases from eukaryotes.

B) Prokaryotic DNA polymerases produce longer Okazaki fragments than eukaryotic DNA polymerases.

C) Eukaryotic DNA polymerases synthesize DNA in the 5’-to-3’ direction, whereas prokaryotic DNA polymerases can synthesize DNA in both directions.

D) Eukaryotic DNA polymerases tend to be multimers while prokaryote DNA polymerases tend to be monomeric.

E) DNA polymerases of eukaryotes do not differ from those of prokaryotes.

Answer 12

B) Prokaryotic DNA polymerases produce longer Okazaki fragments than eukaryotic DNA polymerases.

Question 13

The universal features of DNA replication include

A) release of PPi from a nucleoside triphosphate.

B) synthesis from the 5’ end to the 3’ end.

C) base pairing of A to T and G to C.

D) use of a primer.

E) All of the above

Answer 13

E) All of the above

Question 14

Transcription of specific genes in eukaryotes requires

A) A few types of sigma factors.

B) A single sigma factor.

C) Tissue (or cell)-specific transcription factors

D) Time (developmentally)-specific transcription factors

E) Both C) and D)

Answer 14

E) Both C) and D)

Question 15

How do enhancers differ from promoters?

A) Enhancers do not bind RNA polymerase

B) Enhancers include the upstream (UP) element

C) Enhancers bind the sigma factor

D) There is no difference: enhancer and promoter are synonymous

E) My answer is not here

Answer 15

B) Enhancers include the upstream (UP) element

Question 16

Operons

A) control the expression of constitutive genes.

B) are subject to positive or to negative control.

C) are not affected by mutations in the genes for repressors or inducers.

D) occur in both prokaryotes and eukaryotes.

E) only occur in eukaryotes.

Answer 16

B) are subject to positive or to negative control.

Question 17

Which of the following refers to an exon?

A) Its sequence is translated into protein

B) Its RNA product is removed during mRNA processing

C) Its sequence is not translated into protein

D) It carries an amino acyl residue for translation

E) It is not part of a mature, totally processed mRNA molecule

Answer 17

A) Its sequence is translated into protein

Question 18

There are several kinds of RNA polymerases in eukaryotic cells. Which assertion is incorrect?

A) tRNA is synthesized by RNA pol III

B) RNA pol II produces protein-coding mRNA

C) Most of the rRNA in the cell is produced by RNA pol I

D) All of the above

E) None of the above

Answer 18

E) None of the above

Question 19

Which of the following is a way in which RNA is processed after transcription?

A) Introns are spliced out.

B) The 3’ end of mRNA has a poly-A tail appended.

C) Individual bases are covalently modified.

D) The 5’ end of mRNA has a cap appended.

E) All of the above

Answer 19

E) All of the above

Question 20

Other than transmitting genetic messages, what other roles can RNA have in the cell?

A) RNA trimming

B) Gene silencing

C) Peptidyl transferase activity

D) All of the above

E) None of the above

Answer 20

D) All of the above

Question 21

For codons that encode the same amino acid, there are often one or two nucleotides that are held in common. Why might this be advantageous?

A) This makes harmful mutations less likely.

B) This will allow codons to encode more amino acids in the future.

C) This scheme reduces the number of nucleotides necessary to encode a protein.

D) Deletion of one or two nucleotides from the transcribed mRNA would have no effect on the translated protein.

E) None of the above

Answer 21

A) This makes harmful mutations less likely.

Question 22

Fill in the blanks: The Shine-Dalgarno sequence is a _______ leader segment of prokaryotic mRNA It binds to a _________ sequence on the _______ part of the 30S ribosomal subunit and aligns the mRNA with the ribosome for proper translation, beginning with the _____ start codon.

A) purine rich, pyrimidine rich, 16S rRNA, AUG

B) pyrimidine rich, purine rich, 23S rRNA, UGA

C) purine rich, pyrimidine rich, 5SRNA, UAG

D) pyrimidine rich, purine rich, 16S rRNA, UAA

E) None of the above

Answer 22

A) purine rich, pyrimidine rich, 16S rRNA, AUG

Question 23

Consider a protein made up of 150 amino acid residues. How many GTP molecules will be required if, on average, 2 GTPs are consumed per peptide bond formed (one for elongation positioning and another for translocation)?

A) 150 total

B) 149 total

C) 300 plus 1 for initiation and 1 for termination = 302

D) 298 plus 1 for initiation and 1 for termination = 300

E) Can I use a calculator?

Answer 23

D) 298 plus 1 for initiation and 1 for termination = 300

Question 24

Which of the following statements is incorrect?

A) Translation in eukaryotes uses only mRNA in which introns have been spliced out.

B) With a few known exceptions, both eukaryotes and prokaryotes use fundamentally the same genetic code.

C) In most prokaryotic genes no introns are found and generally speaking no RNA splicing occurs.

D) In both prokaryotes and eukaryotes, protein synthesis occurs by a nucleophilic attack by the a-amino group of the A-site aminoacyl tRNA on the carbonyl of the growing peptide chain.

E) None of the above

Answer 24

C) In most prokaryotic genes no introns are found and generally speaking no RNA splicing occurs.

Question 25

Which of the following types of protein are known to be translated using a CUG start codon?

A) Immune system peptides displayed on the major histocompatibility complex (MHC)

B) Proteins in the cytoskeleton

C) Transcription factors

D) Antibodies

E) Enzymes

Answer 25

A) Immune system peptides displayed on the major histocompatibility complex (MHC)

Question 26

Find the mismatched aldose-ketose pair:

A) D-threose—D-mannose

B) D-glucose—D-fructose

C) Glyceraldehyde—Dihydroxyacetone

D) D-ribulose—D-ribose

E) D-xylose—D-xylulose

Answer 26

A) D-threose—D-mannose

Question 27

From the following, which are characteristics of a reducing sugar?

A) The sugar is an aldose.

B) The sugar is a ketose.

C) The sugar is readily reduced.

D) The sugar is only a hexose.

E) None of the above

Answer 27

A) The sugar is an aldose.

Question 28

What make humans unable to digest plant materials with the effectiveness of fungi and some bacteria?
A) The human genome do not code for cellulases.

B) The enzymatic repertoire of humans does not include glycosidases capable to hydrolyze the b-(1−4) bonds between glucose residues in cellulose.

C) The b-(1−4) bond between glucose molecules in cellulose is much more stable than the a-(1−4) and a-(1−4) bonds in starch (and glycogen).

D) All of the above

E) None of the abov

Answer 28

D) All of the above

Question 29

Consider the following information: phosphoenolpyruvate → pyruvate ΔG°’ = −61.9 kJ/mol
ADP + Pi → ATP ΔG°’ = +30.5 kJ/mol

How many molecules of ATP might theoretically have been produced when coupled to the conversion of one molecule phosphoenolpyruvate to pyruvate? Structural roles, such as cell walls in plants, fungi, Protista, and bacteria

A) 1

B) 2

C) 3

D) 4

E) None of these

Answer 29

B) 2

Question 30

Which pair is mismatched regarding the use or production of ATP by glycolytic enzymes:

A) Hexokinase—Used in reactions that consume ATP

B) Aldolase—Used in reactions that do not involve ATP

C) Phosphofructokinase—Used in reactions that consume ATP

D) Phosphoglycerate kinase—Used in reactions that produce ATP

E) None of the above

Answer 30

E) None of the above

Question 31

The phosphorylation of glucose to glucose 6-phosphate

A) is so strongly exergonic that it does not require a catalyst.

B) is an exergonic reaction not coupled to any other reaction.

C) is an endergonic reaction that takes place because it is coupled to the exergonic hydrolysis of ATP.

D) is an exergonic reaction that is coupled to the endergonic hydrolysis of ATP.

E) None of the above

Answer 31

C) is an endergonic reaction that takes place because it is coupled to the exergonic hydrolysis of ATP.

Question 32

Which of the following best describes the glycosidic bond in the disaccharide shown above?
A) a-(1−4)

B) b-(1−4)

C) a-(2−4)

D) b-(2−4)

E) None of the above

Answer 32

C) a-(2−4)

Question 33

The enzyme hexokinase

A) phosphorylates a number of different sugars, including glucose, fructose, and mannose.

B) specifically phosphorylates glucose rather than other sugars.

C) is the only kinase involved in glycolysis.

D) does not participate in glycolysis.

E) None of the above

Answer 33

A) phosphorylates a number of different sugars, including glucose, fructose, and mannose.

Question 34

Which of the following enzymes interconverts an aldose and a ketose?

A) kinase

B) isomerase

C) mutase

D) dehydrogenase

E) phosphorylase

Answer 34

B) isomerase

Question 35

In glycolysis, ATP is synthesized by

A) substrate-level phosphorylation.

B) oxidative phosphorylation.

C) photophosphorylation.

D) A) and B)

E) A), B) and C)

Answer 35

A) substrate-level phosphorylation.

Question 36

Several of the enzymes of glycolysis fall into classes that are seen often in metabolism. Which of the following description is incorrect?

A) Aldolases cleave aldols into two smaller molecules, one containing a keto group and one being an enol or enol precursor.

B) Dehydrogenases catalyze redox reactions involving NADH + H+ or FADH2 in which the substrate’s oxidation state changes and a hydrogen or hydrogens transfer from the substrate.

C) Isomerases perform molecular rearrangement reactions in which the molecular formula of the substrate does not change, but the isomeric form of the molecule is altered.

D) Kinases transfer phosphate groups from molecules containing high-energy phosphates to substrate molecules.

E) None of the above

Answer 36

E) None of the above

Question 37

Which of the following exercise(s) allosteric control in the reaction of phosphofructokinase?

A) ATP

B) fructose 2,6-bisphosphate

C) ATP and fructose 2,6-bisphosphate

D) ADP and glucose-1-phosphate

E) None of the above

Answer 37

C) ATP and fructose 2,6-bisphosphate

Question 38

Which group of small molecules best fit the boxes associated with the reaction shown?
I. a = ATP, b= ADP, c = H2O

II. a = NADH + H+, b = NAD+, c= Pi

III. a = NAD+, b= NADH + H+, c = H2O

IV. a = NAD+, b = NADH + H+, c = Pi

A) I

B) II

C) III

D) IV

E) None of these

Answer 38

D) IV

Question 39

Why is the formation of fructose-1,6-bisphosphate a likely control step in the glycolytic pathway?

A) Fructose-6-phosphate can be easily stored by the body.

B) The irreversible formation of fructose-1,6-bisphosphate is the first committed step in glycolysis.

C) It has the highest activation energy of any step in glycolysis.

D) All of the above

E) None of the above

Answer 39

B) The irreversible formation of fructose-1,6-bisphosphate is the first committed step in glycolysis.

Question 40

When humans consume ethanol, the first step in its metabolism is:

A) conversion to lactate

B) conversion to acetaldehyde

C) conversion to acetone

D) production of fatty acids

E) conversion to ketone bodies

Answer 40

B) conversion to acetaldehyde

Question 41

Why is the reaction catalyzed by citrate synthase considered a condensation reaction?

A) The number of species bound to a specific carbon in oxaloacetate reduces from four to three.

B) The number of product molecules is greater than the number of reactants.

C) A carbon-carbon single bond is converted to a double bond during the reaction.

D) A C–C bond is formed during the synthesis of citrate.

E) None of the above

Answer 41

D) A C–C bond is formed during the synthesis of citrate.

Question 42

Which of the following reaction aspects is a component of the net reaction catalyzed by a synthetase?

A) A group shifts from one carbon to an adjacent carbon on the substrate.

B) A high-energy phosphate bond is utilized to synthesize a molecule.

C) A reduction or oxidation occurs.

D) All of the above

E) None of the above

Answer 42

B) A high-energy phosphate bond is utilized to synthesize a molecule.

Question 43

NADH + H+ is an important coenzyme in catabolic processes, whereas NADPH + H+ appears in anabolic processes. How can the exchange of NADH + H+ and NADPH + H+ be effected?

A) NADPH + H+ can be imported into the mitochondrion in conjunction with NADH + H+ export from the mitochondrion.

B) NADH + H+ is consumed in the conversion of oxaloacetate to malate, and malate can produce pyruvate and NADPH + H+.

C) The citric acid cycle can be modified to produce NADPH + H+ rather than NADH + H+.

D) NADH + H+ can be converted to nicotine, which then can be metabolized to NADPH + H+.

E) None of the above

Answer 43

A) NADPH + H+ can be imported into the mitochondrion in conjunction with NADH + H+ export from the mitochondrion.

Question 44

Three of the following reactions act as control points in the citric acid cycle, i.e., they are the most favorable reactions. Which one is not a control point?

A) Oxaloacetate + Acetyl-CoA + H2O → CoA-SH + Citrate

B) Isocitrate + NAD+ → a-Ketoglutarate + CO2 + NADH + H+

C) a-Ketoglutarate + CoA-SH + NAD+ → Succinyl-CoA + CO2 + NADH + H+

D) Citrate → Isocitrate

E) None of the above

Answer 44

D) Citrate → Isocitrate

Question 45

Which of the following statements explains why acetyl-CoA is considered the central molecule of metabolism?

A) Acetyl-CoA feeds directly into the citric acid cycle.

B) Acetyl-CoA contains a thioester bond that makes it one of the high energy compounds in metabolic pathways.

C) Acetyl-CoA can be formed from many compounds, such as fats, carbohydrates, and many amino acids.

D) Acetyl-CoA can form fats and ketone bodies.

E) All of the above

Answer 45

E) All of the above

Question 46

Why is the citric acid cycle considered as part of aerobic metabolism, even though O2 does not appear in any reaction?

A) The reducing units produced by the citric acid cycle couple to aerobic ATP production mediated by the electron transport chain.

B) The citric acid cycle can function in the presence of O2.

C) Oxidation can occur in the absence of molecular oxygen.

D) None of the components of the citric acid cycle are reduced as the cycle progresses.

E) CO2 is produced in the cycle proper and during the production of acetyl-S-CoA.

Answer 46

A) The reducing units produced by the citric acid cycle couple to aerobic ATP production mediated by the electron transport chain.

Question 47

Why are all the reactions of electron transport, when written as redox half reactions, written with the electrons on the reactant side?

A) Because these are half reactions, they always run in the direction with electrons as reactants.

B) The reactions of the electron transport chain all run in this direction.

C) The reactions do not run in the reverse direction, i.e. with the electrons as products.

D) The chemical convention for redox half reactions is to write them as reductions.

E) None of the above

Answer 47

D) The chemical convention for redox half reactions is to write them as reductions.

Question 48

What unusual property do cytochromes have in common with hemoglobin or myoglobin?

A) They all bind strongly to RNA as well as small ligands.

B) All of them contain heme groups.

C) All of them participate in electron transfers in biological reactions.

D) They all are found in plants, animals, and bacteria.

E) All of the above

Answer 48

B) All of them contain heme groups.

Question 49

Which of the following statements explains why acetyl-CoA is considered the central molecule of metabolism?

A) Acetyl-CoA feeds directly into the citric acid cycle.

B) Acetyl-CoA contains a thioester bond that makes it one of the high energy compounds in metabolic pathways.

C) Acetyl-CoA can be formed from many compounds, such as fats, carbohydrates, and many amino acids.

D) Acetyl-CoA can form fats and ketone bodies.

E) All of the above

Answer 49

E) All of the above

Question 50

Why is the citric acid cycle considered to be part of aerobic metabolism, even though molecular oxygen does not appear in any reaction?

A) The reducing units produced by the citric acid cycle couple to aerobic ATP production mediated by the electron transport chain.

B) The citric acid cycle can function in the presence of O2.

C) Oxidation can occur in the absence of molecular oxygen.

D) None of the components of the citric acid cycle are reduced as the cycle progresses.

E) CO2 is produced in the cycle proper and during the production of acetyl-S-CoA.

Answer 50

A) The reducing units produced by the citric acid cycle couple to aerobic ATP production mediated by the electron transport chain.

Question 51

What is the underlying reason for the difference in the yield of ATP from the complete oxidation of one mole of glucose in brain cells compared to that in kidney cells?

A) The level of dissolved O2 is greater in kidney cells than it is in brain cells.

B) Glucose transport to brain cells is less efficient than it is to kidney cells.

C) The ATP synthase complex is less efficient in brain cells compared to kidney cells.

D) The brain cells use the glycerol-phosphate shuttle whereas the kidney cells use the malate-aspartate shuttle.

E) None of the above

Answer 51

D) The brain cells use the glycerol-phosphate shuttle whereas the kidney cells use the malate-aspartate shuttle.

Question 52

Is the production of glucose and O2 from CO2 and H2O in photosynthesis a spontaneous process?

A. Yes: the overall biosynthesis of glucose has a delta G > 0

B. No: electromagnetic energy is converted to chemical energy as ATP and reducing power as NADPH + H+

Answer 52

B. No: electromagnetic energy is converted to chemical energy as ATP and reducing power as NADPH + H+

Question 53

which of the following molecules does not have hydrogen bonds as important components controlling its structure?

A. DNA

B. tRNA

C. Hemoglobin

D. Cholesterol

E. Silk

Answer 53

D. cholesterol

Question 54

The amino and carboxyl groups of amino acids are bonded to which C?

A. both are bonded to the alpha C

B. both are bonded to the beta C

C. the amino is bonded to the alpha C, and the carboxyl is bonded to the beta C

D. the amino is bonded to the beta-C, and the carboxyl is bonded to the alpha-C

E. none of the above

Answer 54

D. the amino is bonded to the beta-C, and the carboxyl is bonded to the alpha-C

Question 55

which of the following statements regarding hydrogen bonding in secondary structures is true?

A. both alpha helices and beta sheets only use intrachain hydrogen bonds

B. both alpha helices and beta sheets only use interchain hydrogen bonds

C. alpha helices only use intrachain hydrogen bonds and beta sheets can use either intrachain or interchain bonds

D. alpha helices can use either intrachain or interchain hydrogen bonds and beta sheets only use interchain H bonds

E. none of the above

Answer 55

C. alpha helices only use intrachain hydrogen bonds and beta sheets can use either intrachain or interchain bonds

Question 56

Consider the oligopeptide Cys-Ala-Gly-Arg-Gln-Met. what is the overall net charge on this peptide at pH 7?

A. + 2

B. + 1

C. 0

D. - 1

E. - 2

Answer 56

B. + 1

Question 57

In allosteric interactions:

A. proteins that consist of a single polypeptide chain form aggregates

B. disulfide bonds are broken by reduction

C. changes that take place in one site of a protein cause changes at a distant site

D. all of the above

E. none of the above

Answer 57

C. changes that take place in one site of a protein cause changes at a distant site

Question 58

the protein myoglobin:

A. contains a high degree of beta pleated sheet structure

B. carries oxygen in the bloodstream

C. binds oxygen cooperatively

D. All of the above

E. none of the above

Answer 58

E. none of the above

Question 59

the affinity of fetal hemoglobin for oxygen:

A. has not been sufficiently studied

B. is the same as that of adult hemoglobin

C. is lower than that of maternal hemoglobin

D. is higher than that of maternal hemoglobin

E. is the same as that of myoglobin

Answer 59

D. is higher than that of maternal hemoglobin

Question 60

In the Bohr effect the binding of oxygen to hemoglobin:

A. is increased by the presence of Na+

B. is increased by the presence of H+ and CO2

C. Is decreased by the presence of H+ and CO2

D. is enhanced by the presence of CO

E. is unchanged All of the above

Answer 60

C. Is decreased by the presence of H+ and CO2

Question 61

The binding of oxygen to hemoglobin differs from the oxygen-binding behavior of myoglobin because:

A. oxygen binding to hemoglobin is cooperative

B. oxygen binding to myoglobin is cooperative

C. the oxygen-binding curve of hemoglobin is hyperbolic

D. all of the above

E. none of the above

Answer 61

A. oxygen binding to hemoglobin is cooperative

Question 62

the purity of a protein enzyme at various stages of purification is best measured by:

A. total protein (e.g. mg/mL)

B. total enzyme activity

C. specific activity of the enzyme (units/mg)

D. % (w/v) recovery of protein

E. % (w/w) recovery of the enzyme

Answer 62

C. specific activity of the enzyme (units/mg)

Question 63

a protein enzyme is more advantageous than a nonenzymatic catalyst because

A. it is highly specific

b. it can function in a wide range of pH values

C. its conformation is not affected by high temperature

D. it can function in an organic solvent with the same efficiency as it does in water

E. it can modify the free energy of the reaction it participates in

Answer 63

A. it is highly specific

Question 64

enzymatic activity has an optimum temperature because

A. the component amino acids have varying melting points

B. the rate of reactions is thermodynamically controlled

C. the side chains of essential residues are chemically degraded at higher temperatures

D. raising the temperature speeds up the reaction until protein denaturation sets in

E. the organism producing the enzyme dies beyond a certain temperature

Answer 64

D. raising the temperature speeds up the reaction until protein denaturation sets in

Question 65

how is the Vmax related to turnover number of an enzyme?

A. Vmax is the turnover number multiplied by the free plus substrate-bound enzyme concentrations (ET).

B. Vmax is equivalent to the turnover number divided by the free enzyme concentration [E]

C. Vmax is the turnover number multiplied by Km

D. Vmax is the turnover number multiplied by the substrate-bound enzyme concentration [ES]

E. Vmax is the free plus substrate-bound enzyme concentration [ET] divided by the turnover number

Answer 65

A. Vmax is the turnover number multiplied by the free plus substrate-bound enzyme concentrations (ET).

Question 66

which of the following are valid reasons for carrying out enzymatic reactions in buffer solutions:

A. some enzyme-catalyzed reactions produce OH- ions

B. Some enzyme-catalyzed reactions produce H+ ions

C. enzyme activities are often strongly pH dependent

D. all of the above

E. none of the above

Answer 66

D. all of the above

Question 67

an enzyme catalyzes the formation of ATP from ADP and inorganic phosphate ion. what is its effect on the rate of hydrolysis of ATP to ADP and phosphate?

A. the catalyst will not alter the rate of the reaction ATP –> ADP + phosphate

B. the rate of the reaction ATP –> ADP + phosphate will be enhanced by the same factor as the rate for ADP + phosphate –> ATP

C. the rate of the reaction ATP –> ADP + phosphate will increase, but by a smaller factor than for the reaction ADP + phosphate –> ATP

D. The rate of the reaction ATP –> ADP + phosphate will decrease by the same factor that the rate for ADP + phosphate –> ATP increased

E. none of the above

Answer 67

B. the rate of the reaction ATP –> ADP + phosphate will be enhanced by the same factor as the rate for ADP + phosphate –> ATP

Question 68

for an enzyme that obeys michaelis-menten kinetics, if [S] = Km, then the proportion V/Vmax = … . The original form of the Michaelis-Menten equation is V = Vmax[S] / Km + [S]

A. 0.1%

B. 0.5%

C. 5%

D. 10%

E. 50%

Answer 68

E. 50%

Question 69

for an enzymatically catalyzed reaction in which the measured values for Km and Vmax are, respectively, 13.9 mM and 3.10 mM/min, what is the value of the turnover number? the concentration of enzyme used in the reaction is 200 microM. recall that the turnover number is also called the Kcat.

A. 69.5 min^-1

B. 22.4 min^-1

C. 15.5 min^-1

D. none of the above

E. there is not enough info

Answer 69

C. 15.5 min^-1

Question 70

which of the following is implied by induced fit between the enzyme’s active site and substrate?

A. the enzyme is a flexible molecule

B. an enzyme will work equally well with different substrates

C. an active site can bind to different substrates

D. enzymes are flexible molecules, therefore some of them may bind different substrates

E. all of the above

Answer 70

E. all of the above

Question 71

in the reaction catalyzed by aspartate transcarbamoylase, when the rate is plotted against the concentration of substrate a sigmoidal graph is obtained. it follows that:

A. aspartate transcarbamoylase is an allosteric enzyme

B. the graph shows that noncooperative kinetics are observed

C. the graph indicates that the reaction is zero order

D. the graph is characteristic of a nonallosteric enzyme

E. none of the above

Answer 71

A. aspartate transcarbamoylase is an allosteric enzyme

Question 72

what are the correct labels for enzymatic reaction mechanisms?

A. 1 = random, 2 = ping-pong, 3 = ordered

B. 1 = ping-pong, 2 = ordered, 3 = random

C. 1 = ordered, 2 = random, 3 = ping-pong

D. 1 = ping-pong, 2 = random, 3 = ordered

E. none of thea bove

Answer 72

C. 1 = ordered, 2 = random, 3 = ping-pong

Question 73

The Km of hexokinase for glucose = 0.15 mM and for fructose, Km = 1.5 mM. which is the preferred substrate?

A. Glucose

B. fructose

C. neither substrate is preferred over the other

D. you cannot tell from the data given

E. none of these answers

Answer 73

a. glucose

Question 74

how can competitive and noncompetitive inhibition be distinguished in terms of Km?

A. the apparent value of Km decreases with a competitive inhibitor, while it remains unchanged with a noncompetitive inhibitor

B. the apparent value of km increases with a competitive inhibitor, while it decreases with a noncompetitive inhibitor

C. the apparent value of Km increases with a competitive inhibitor, while it remains unchanged with a noncompetitive inhibitor

D. the apparent value of Km remains unchanged with a competitive inhibitor, while it increases for a noncompetitive inhibitor

E. none of the above

Answer 74

C. the apparent value of Km increases with a competitive inhibitor, while it remains unchanged with a noncompetitive inhibitor

Question 75

enzyme inhibition can be overcome under some, but not all, conditions. under what conditions can inhibition be overcome?

A. a competitive inhibitor can always be overcome by the addition of enough substrate, while a noncompetitive inhibitor can be overcome only if the inhibitor is reversible

B. a competitive inhibitor, if it is reversible, can be overcome by the addition of enough substrate, while a noncompetitive inhibitor can never be overcome

C. a competitive inhibitor can always be overcome by the addition of enough substrate, while a noncompetitive inhibitor can never be overcome

D. a noncompetitive inhibitor can always be overcome by the addition of enough substrate, while a competitive inhibitor can never be overcome

E. none of the above statements is correct.

Answer 75

C. a competitive inhibitor can always be overcome by the addition of enough substrate, while a noncompetitive inhibitor can never be overcome

Question 76

you are studying the psychopharmacological effects of lithium. your literature searches indicate that, in the neuron, Li+ interferes with the metabolism of the secondary messengers polyphosphoinositide and inositol via uncompetitive inhibition of the enzyme inositol monophosphatase. what is the action of lithium on the target enzyme?

A. it competes with phosphate for the active site

B. it binds the enzyme in a region other than the active site

C. it only binds to the enzyme-substrate complex

D. it only binds to the free enzyme

E. none of the above

Answer 76

C. it only binds to the enzyme-substrate complex

Question 77

which of the following proteins, is not subject to the control of zymogen activation?
A. pepsin

B. trypsin

C. hemoglobin

D. chymotrypsin

E. none of the above undergoes zymogen activation

Answer 77

C. hemoglobin

Question 78

which of the following amino acids are commonly phosphorylated by kinase-mediated reactions?

A. methionine

B. tyrosine

C. valine

D. arginine

E. histidine

Answer 78

B. tyrosine

Question 79

the concerted and sequential models can predict the behavior of allosteric enzymes. which statement is correct?

A. in both the concerted and the sequential model, the binding of substrate to an enzyme subunit alters the affinity of the substrate for other subunits of the enzyme

B. in the sequential model, enzyme subunits can be in either the R or the T form, independent of each other

C. all enzyme subunits are in the same form, either R or T in the concerted model

D. all of the above

E. none of the above

Answer 79

D. all of the above

Question 80

In terms of enzyme nomenclature, what is a K system?

A. an enzyme for which Km does not vary as inhibitor concentration varies

B. an allosteric enzyme in which the binding of an effector alters the apparent affinity of the enzyme for its substrate without changing the apparent Vmax of the reaction

C. an enzyme-substrate pair in which plots of 1/V vs. 1/[S] of kinetic data taken at different effector concentrations form straight lines that intersect on the 1/V axis at 1/V = 1/Vmax

D. an allosteric enzyme in which the binding of an effector alters the apparent Vmax of the enzyme-substrate reaction without altering the affinity of the enzyme for its substrate

E. an allosteric enzyme system for which the apparent value of Km/ Vmax is constant as a function of inhibitor concentration

Answer 80

B. an allosteric enzyme in which the binding of an effector alters the apparent affinity of the enzyme for its substrate without changing the apparent Vmax of the reaction

Question 81

nucleophilic catalysis is important in the reaction mechanism that trypsin uses for the hydrolysis of proteins. in the first step of the catalytic mechanism, the .. atom of … acts as a nucleophile to attack a peptide bond in the substrate. in the second step of the mechanism, the … atom of … acts as a nucleophile to cleave a bond, producing the final leaving group in the rxn.

A. N, lys, S, Met

B. O, Ser, O, water

C. N, his, S, cys

D. O, water, N, lys

E. none

Answer 81

`B. O, Ser, O, water

Question 82

an enzyme that transfers a phosphate moiety in a reaction is called a … the most common source of phosphate for biochemical reactions is …
A. protease, inorganic phosphate ion

B. phosphatase, inorganic phosphate ion

C. kinase, ATP

D. phosphatase, ATP

E. kinase, phosphoenolpyruvate

Answer 82

C. kinase, ATP

Question 83

an immunogen (a molecule that elicits an antibody response) leads to the formation of antibodies with catalytic activity if the immunogen mimics the transition state of a reaction. the resulting catalytic antibodies are also known as abzymes. catalytic antibodies have been used in the treatment of … addiction

a. cocaine
b. mescaline
c. psylocibin
d. opioid
e. cannibinoids

Answer 83

a. cocaine

Question 84

allosteric enzymes do not follow michaelis-menten kinetics, therefore the parameter … can be used to analyze the effect of inhibitors and activator because it is analogous of … 
A. Ki, Km 
b. Ki, K0.5
C. K0.5, Km 
D. Km, K0.5 
E. none of the above

Answer 84

C. K0.5, Km

Question 85

a velocity curve  (V vs [S]) for a typical allosteric enzyme will be 
A. a sigmoid curve 
B. a rectangular hyperbola 
C. a straight line 
D. a parabola
E. none of the above

Answer 85

A. a sigmoid curve

Question 86

ATP is a negative allosteric effector for glycogen phosphorylase. this is an example of:

A. feedback inhibition 
B. positive cooperativity
C. negative cooperativity
D. competitive inhibition 
E. uncompetitive inhibition

Answer 86

A. feedback inhibition

Question 87

how are coenzymes and vitamins related?

A. vitamins are often precursors to coenzymes

B. coenzymes are often precursors to vitamins

C. coenzymes are used in metabolic pathways to synthesize vitamins

D. coenzymes and vitamins both belong to the class of biomolecules found in health stores

E. vitamins are used in metabolic pathways to synthesize coenzymes

Answer 87

A. vitamins are often precursors to coenzymes

Question 88

the freeze-fracture technique of electron microscopy is usefull in studying membrane structure because:

A. integral membrane proteins can be seen in association with one leaflet of the lipid bilayer

B. all the proteins can be removed from the membrane

C. the degree of order of the lipid bilayer can be determined

D. the presence of bound carbohydrates can be detected

E. none of the above

Answer 88

A. integral membrane proteins can be seen in association with one leaflet of the lipid bilayer

Question 89

briefly washing cells in a buffered solution at pH 11 is effective for isolating a cell membrane-associated hormone receptor. (A standard growth solution for animal cells has pH 7). which of following best fits this description?

A. this is an integral membrane protein that completely traverses the cell membrane

B. this is an integral membrane protein that only penetrates one leaf of the cell membrane

C. this is a peripheral membrane protein that probably interacts with membrane phospholipids using aspartate-mediated salt bridges

D. this is a peripheral membrane protein that probably interacts with membrane phospholipids using lysine-mediated salt bridges

E. none

Answer 89

D. this is a peripheral membrane protein that probably interacts with membrane phospholipids using lysine-mediated salt bridges

Question 90

crotoxin is a phospholipase A2 neurotoxin present in the venom of some South American snakes. what type of bonds do lipases break in order to release fatty acids?

A. carboxylic esters

B.. hemiacetals

C. ethers

D. phosphate monoesters

E. beta-lactam

Answer 90

A. carboxylic esters

Question 91

liposomes are

A. single-layered membranes

b. artificial membrane-bounded structures used to deliver medications or recombinant DNA

C. mixed micelles involved in cholesterol transport among cells

d. bilayers with the hydrophobic regions on the outside
e. none

Answer 91

b. artificial membrane-bounded structures used to deliver medications or recombinant DNA

Question 92

which of the following treatments would be most useful in separating an integral membrane protein from the lipid component of a cell membrane while retaining the protein’s activity?

A. drastically change the pH

B. add a mild detergent

C. add a salt at a high concentration

D. add a mixture of proteases

E. none of these: you can’t separate an integral membrane protein from the lipid without losing activity

Answer 92

B. add a mild detergent

Question 93

the myelin sheaths of neurons typically contain large amounts of:’

A. waxes

B. triacylglycerols

C. cholesterol

D. sphingolipids

E. none of the above

Answer 93

D. sphingolipids

Question 94

in the fluid mosaic model of membrane structure:

A. the proteins are specifically bonded to the lipids

B. the proteins “float” in the lipid bilayer

C. the proteins are sandwiched between the lipid molecules

D. the lipids are sandwiched between the protein molecules

E. none of the above

Answer 94

B. the proteins “float” in the lipid bilayer

Question 95

irreversible inhibitors of enzymatic reactions:

A. bind to the enzyme only at lwo temps

B. affect only serine side chains

C. react with the enzyme to produce a protein that is not enzymatically active and from which the original enzyme cannot be regenerated

D. are bound to the enzyme by the lock-and-key mechanism

E. none

Answer 95

C. react with the enzyme to produce a protein that is not enzymatically active and from which the original enzyme cannot be regenerated

Question 96

which of the following would not be enriched on the outer leaflet of the lipid bilayer compared to the inner leaflet?

a. phosphoacylglycerol
b. ganglioside
c. cerebroside
d. sphingomyelin
e. none

Answer 96

a. phosphoacylglycerol

Question 97

you are isolating a protein (G) using an affinity-chromatography column. protein g binds ligand h. the column contains a matrix whose particles are covalently bound to h. what would be the last step to release the protein of interest from the matrix?

A. add an excess of the mixture containing protein G

B. wash with an acidic or basic buffer (i.e., with two pH units lower or higher than the elution buffer)

C. add solution with an excess of free ligand h in the same elution buffer

D. add an excess of free matrix particles

E. no one uses affinity chromatography for protein purification anymore. everyone does cloning!

Answer 97

C. add solution with an excess of free ligand h in the same elution buffer

Question 98

heating a solution containing an enzyme markedly decreases the enzyme’s activity. if the solution contains a high amount of substrate this decrease might be reduced? what might be the reason for such reduction?

A. increasing the substrate concentration will lower the activation energy of the catalyzed reaction

B. the free energy of the reaction will increase in proportion to the concentration of substrate to make the reaction more favorable

C. saturating the enzyme will increase the reaction rate

D. substrate binding to the enzyme will help stabilize the enzyme structure

E. none of the above

Answer 98

D. substrate binding to the enzyme will help stabilize the enzyme structure

Question 99

the active site of an enzyme:

A. is frequently located in a cleft in the enzyme

B. is the portion of the enzyme that binds the substrate

C. contains the reactive groups that catalyze the reaction

D. all of the above

E. none of the above

Answer 99

D. all of the above

Question 100

which of the following statements about leukotrienes is false?

A. they are carboxylic acid-containing lipids

B. they are known to inhibit the aggregation of platelets

C. they are derived from arachidonic acid

D. they have three conjugated double bonds

E. they have 20 C atoms in their carboxylic acid backbone

Answer 100

B. they are known to inhibit the aggregation of platelets

Question 101

which of the following statements about prostaglandins is true?

A. they were first detected in seminal fluid, which is produced by the prostate

B. they are derived from arachidonic acid

C. they are present in a wide variety of tissues in mammals

D. all fo the above

E. none

Answer 101

D. all fo the above

Question 102

which of the terms best refers to enzyme reactions that induce a single-stranded break in supercoiled DNA, relax the supercoiling, and reseal the break?

A. positive supercoiling

B. negative supercoiling

C. topoisomerase activity

D. primase activity

E. supercoiling

Answer 102

C. topoisomerase activity

Question 103

in oxidative phosphorylation, ATP production is coupled to the events in the electron-transport chain. what is accomplished in the final electron transfer event in the electron-transport chain?

A. OH- is oxidized to O2

B. pyruvate is oxidized to CO2

C. O2 is reduced to H2O

D. NAD+ is reduced to NADH + H+

E. none of the above

Answer 103

C. O2 is reduced to H2O

Question 104

which of the following statements is correct regarding the function of heterotrimeric G protein function?

A. a cascade of events must occur that ultimately activate protein kinase C

B. binding of a hormone to a receptor must signal the exchange of GDP for GTP

C. binding of GTP to the receptor protein must induce a change in conformation of the receptor

D. binding of cAMP to the subunit of the G protein must initiate translocation of the subunit

E. all

Answer 104

B. binding of a hormone to a receptor must signal the exchange of GDP for GTP

Question 105

where does oxidative phosphorylation take place in the animal cell and what other processes are required for this to occur?

A. it takes place in the mitochondrion and follows the production of NADH + H+ and FADH2

B. it takes place in the mitochondrion and immediately follows glycolysis

C. it takes place in the smooth endoplasmic reticulum and requires lipid biosynthesis

D. none of the above

Answer 105

A. it takes place in the mitochondrion and follows the production of NADH + H+ and FADH2

Question 106

which of the following would decrease activity of the citric acid cycle overall?

I. high concentration of NADH

II. high concentration of Ca2+

III. high concentration of ATP

IV. high concentration of citrate

A. I only

B., I, II, III, IV

C. I, III

D. I, III, IV

E. I, IV

Answer 106

D. I, III, IV

Question 107

which of the following is an intermediate between citrate and isocitrate in the citric acid cycle?

A. succinyl-CoA

B. citryl-coA

c. oxalosuccinate
d. succinyl-phosphate

E. cis-aconitate

Answer 107

E. cis-aconitate

Question 108

which of the following is an intermediate between citrate and isocitrate in the citric acid cycle?

A. read-through of stop codons

B. substitution of lysine for isoleucine

C. substitution of lysine for tyrosine

D. substitution of lysin for phenylalanine

Answer 108

B. substitution of lysine for isoleucine

Question 109

which of the following statements is most accurate regarding the reaction shown above ?

6-phosphogluconate + NADP+ –> beta-keto acid intermediate –> Ru5P

A. the enzyme that catalyzes this reaction si regulated by its production

b. this reaction is catalyzed by 6-phosphogluconate dehydrogenase, an enzyme regulated by its product
c. this reaction is catalyzed by 6-phosphoglocuonate dehydrogenase
d. the reaction is an oxidative carboxylation: the enzyme that catalyzes it is regulated by its product
e. this reaction is an oxidative carboxylation rxn

Answer 109

c. this reaction is catalyzed by 6-phosphoglocuonate dehydrogenase

Question 110

If Z = ATP formed via substrate level phosphorylation in the diagram below, which of the following compounds (represented by an uppercase letter) contains a high-energy bond?

A. Compound A

B. compound B

C. compound c

d. all have equally high energy
e. all have equally low energy

Answer 110

B. compound B

Question 111

Ras is an example of:

A. a kinase-activated protein

b. a protein anchored by prenylation
c. a gtp-dependent protein
d. all
e. none

Answer 111

d. all

Question 112

the activity of protein kinase A is affected by which of the following?

a. caffeine
b. phosphodiesterases
c. levels of cAMP
d. cholera toxin
e. all

Answer 112

e. all

Question 113

the insulin signaling pathway includes which of the following steps??

a. ligand-induced dimerization of the receptor and phosphorylation of IRS-1 and/or IRS-2 proteins
b. autophosphorylation and phosphorylation of iRS-1 and/or IRS-2 proteins

C. IRS-1 induced dimerization of the receptor, autophosphorylation, and phosphorylation of SH2 domains

D. autophosphorylation and dephosphorylation of IRS-1 and/or SH2 domains

E. none of thea bove

Answer 113

b. autophosphorylation and phosphorylation of iRS-1 and/or IRS-2 proteins

Question 114

which of the following is an advantage of protein phosphorylation in regards to biochemical signaling?

A. phosphorylation results in covalent modification of enzymes

b. phosphorylation can be amplified by cascade systems
c. phosphorylation is rapid and specific
d. phosphorylation is enzymatically reversible
e. all

Answer 114

e. all

Question 115

find the incorrect statement regarding heterotrimeric G proteins:

a. they function as an autoinhibitory segment of larger signaling proteins
b. they can function as a mediator to adenylate cyclase activity
c. they are anchored to the cytoplasmic side of the membrane
d. they consist of three subunits, namely, Galpha, Gbeta, and Ggamma

E. none

Answer 115

a. they function as an autoinhibitory segment of larger signaling proteins

Question 116

it has been observed that Ser can be replaced by another amino acid with the least effect on protein structure and function. which of the following is the most reasonable explanation for this observation?

a. due to its small side chain, Ser does not form H bonds very readily with other amino acid residues
b. serine does not form salt bridge interactions
c. serine is sterically free to adopt many conformations within a protein
d. serine has a small side chain that can exist reasonably well in either a polar or a nonpolar environment
e. none of the above

Answer 116

d. serine has a small side chain that can exist reasonably well in either a polar or a nonpolar environment

Question 117

zwitterions are molecules/ions that have separate positively and negatively charged groups. what makes them desirable buffers?

a. zwitterions are usually considered less likely to interfere with biochemical rxns than other buffers
b. zwitterions can take up twice as many H+ ions per buffer molecule as compared to a standard buffer
c. zwitterions can release twice as many H+ ions per buffer molecule as compared to a “standard” buffer
d. zwitterions tend to form dimeric species that increase the buffering capacity of the solution
e. the multiple charges on zwitterions produce a neutrally charged buffer species

Answer 117

a. zwitterions are usually considered less likely to interfere with biochemical rxns than other buffers

Question 118

how are H bonds involved in the transfer of genetic information?

A. h-bonds help stabilize the DNA double helix

B. H-bonds regulate the secondary structure of RNA

C. H-bonds between nucleic acids and water allow DNA and RNA to exist in aqueous solutions

D. H-bonds allow for the complementation of RNA to DNA

E. all of the abov e

Answer 118

D. H-bonds allow for the complementation of RNA to DNA

Question 119

what is the ration of [hepes]/[hepes-H+] buffer

A. .15

B. .71

C. 1. 4

D. 7.63

E. none

Answer 119

b. .71

Question 120

collage IV, which occurs in basement membranes of mammals, contains sulfamiline bonds that crosslinks two collagen triple helices. identify the parent amino acid residues that participate in this linkage

A. threonine, methionine

B. 5-hydroxylysine, cysteine

C. 3-hydroxylysine, cysteine

D. 5-hydroxylysine, methionine

E. 3-hydroxyllysine, methionine

Answer 120

D. 5-hydroxylysine, methionine

Question 121

find the mismatched molecule type with its caloric content

A triacylglycerols - 9Cal/g

B. carbohydrates - 4 Cal/g

C. Proteins - 4 Cal/g

D. all

E. none

Answer 121

E. none

Question 122

a membrane consists of 54% protein by weight and 46% phosphoglycerides by weight the average moleculear weight of lipids is 835 Da and thea verage molecular weight of the proteins is q513000 Da. what is the molar ratio of lipid to protein

A. 1.17

B. 52.4

C. 61.4

D. 82.5

E. none

Answer 122

B. 52.4

`

Question 123

which of the following statements is incorrect concerning the advantages of using allosteric rather than orthosteric drugs?

A. allosteric drugs give rise to an on/off response, allowing for a more rapid change in receptor signal than orthosteric drugs

b. allosteric drugs can be safter bc they have no effect at all unless the natural ligand is present

C. allosteric effectros bind at a site other than the active site, hence are more specific for one or a few receptor types

D. allosteric drugs can enhance or reduce the signal caused by a receptor, whereas orthosteric drugs can only inhibit receptor signals

E. none of the above

Answer 123

A. allosteric drugs give rise to an on/off response, allowing for a more rapid change in receptor signal than orthosteric drugs

Question 124

in oxygenated hemoglobin, pKa = 6.6 for the histidine residues at position 146 on the beta chains. in deoxygenated hemoglobin, the pKa of these residues is 8.2. this data indicates that deoxygenated hemoglobin is … than oxygenated hemoglobin. this change in the pKa of the histidine residues underlies the Bohr effect, in which … in the hydrogen ion concentration reduces the affinity of hemoglobin for O2.

A. stronger, an increase

B. weaker, a decrease

C. stronger, a decrease

D. weaker, an increase

E. none

Answer 124

D. weaker, an increase

Question 125

fibrous and globular proteins can be similar in amino acid composition but they are different in

A. biological function

B. solubility in water

C. molecular shape

D. all

e. none

Answer 125

D. all

Question 126

which of the following amino acids has a lateral R group that will not contribute to a protein’s charge after participating in peptide bond formation?

A. Glu

B. Asp

C. Gln

D. Arg

E. Lys

Answer 126

C. GLn

Question 127

which of the following is false regarding cofactors

A. cofactor si a broad term used for all substance that contribute ot an enzyme’s successful catalytic activity

B. some metals are used as cofactors in their ionic form

C. all enzymes depend on cofactors in order to perform their catalytic activities

D. cofactors include organic groups known as coenzymes

E. cosubstrates are cofactors transiently associated with a given enzyme

Answer 127

C. all enzymes depend on cofactors in order to perform their catalytic activities

Question 128

When the cardiac glycoside digitoxin is used for heart failure, the effects include:

a. inhibition of phosphate hydrolysis from E2 of the [Na+-K+] - ATPase pump
b. activation of the [Na+-K+]-ATPase pump
c. increase in intracellular [Na+]
d. increase in Ca2+ concentration in the sarcoplasmic reticulum

A. a, c, d

B. a, c

C. a, b, c, d

D. b, c, d

E. b, c,

Answer 128

A. a, c, d

Question 129

at equilibrium in solution, D-glucose consists of a mixture of its anomers. which statement most accurately describes this solution?

A. the solution consists of approximately equal amounts of the alpha- and beta- anomers

B. the straight-chain form is present in high concentration

C. the alpha-anomer is more stable and is slightly preferred over the beta-anomer

D. the beta-anomer is more stable and predominates over the alpha-anomer by a ratio of approximately 2: 1

E. none of the above statements is correct

Answer 129

D. the beta-anomer is more stable and predominates over the alpha-anomer by a ratio of approximately 2: 1