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Multiple Choice
Chapter 1: Introduction to Biochemistry
1. Which of the following structures depicts an amide linkage?
A.
B.
C.
D.
E.
2. Which of the following SI unit prefixes are listed in correct order?
A. milli > nano > micro B. micro > milli > nano C. milli > micro > nano
D. nano > milli > micro E. nano > micro > milli
3. Proteins are biopolymers composed of monomers of:
A. amino acids
B. nucleic acids
C. sugars
D. fatty acids E. None of the above
4. The physical property that allows lipids to form membranes:
A. They polymerize readily B. Tight binding to proteins C. Inherent flexibility
D. They are amphipathic. They have hydrophobic tails and hydrophilic heads.
E. High degree of reactivity.
5. Under what thermodynamic conditions will a reaction proceed
spontaneously?
A. G < 0 B. S < 0 C. H < 0
D. G = 0
E. G > 0
6. Though the presence of self-replicating molecules was essential for the
origin of life, what could be considered as the essential requirement for the
construction of a cell?
A. The presence of proteins, nucleic acids and polysaccharides.
B. None of the above are essential. C. Membranes D. Enzymes E. DNA
7. In 1993, Dr. Norman Pace and coworkers discovered a bacteria, Epulopiscium
fishelsoni that are much larger in diameter (80 祄) than the average bacteria (0.5 祄).
Why did this finding cause a stir?
A. It was previously thought that the limit to the size of bacterial cell walls was 50 祄.
B. It was found in the gut of a sturgeon fish.
C. A high surface area to volume ratio was thought to be essential for nutrient diffusion
throughout prokaryotic cells.
D. Bacteria of this size were thought to be too large to move under their own propulsion.
E. These bacteria are too large to have an average-sized prokarotic genome.
8. The energy-producing organelles in eukarotic cells are:
A. golgi
B. endoplasmic reticulum
C. lysosomes
D. mitochondria
E. nucleus
9. Mitochondria and chloroplasts share a number of features in common.
Which of the following is NOT one of them?
A. Both contain DNA
B. Both are surrounded by a double membrane
C. Both are found in all eukaryotic cells
D. Both are important sites of energy conversion
E. Both are derived from symbiotic bacteria that invaded primative eukaryotic cells
10. The cytoskeletal element that is found in cilia and flagella is:
A. All of the above
B. intemediate filaments.
C. microtubules.
D. None of the above
E. actin
11. One of the striking features of the depiction of an E. coli cell by David S.
Goodsell (Figures 1 .25 and 1. 26) is the high concentration of proteins in the
cell. From the image at the top of page 25 and the description in the text,
calculate the number of ribosomes per cell. Which of the following is closest to
your calculation?
A. 25,000
B. 250
C. 250,000
D. 25
E. 2,500
12. The ultimate source of energy for most life on earth is:
A. geothermal heat
B. light
C. glucose
D. fossil fuels
E. ATP
13. Which of the following cellular dimensions is the largest?
A. The distance across a lipid bilayer
B. The diameter of a ribosome
C. The diameter of a molecule of glucose
D. The diameter of a tRNA molecule
E. The diameter of a DNA double helix
14. If the chemical reaction A -> B + C has a positive
temperature will:
G, increasing the
A. increase the entropy of the reaction
B. decrease the ability of the reaction to proceed spontaneously
C. increase the enthalpy of the reaction
D. increase the ability of the reaction to proceed spontaneously
E. None of the above
15. The primary characteristic that distinguishes prokaryotes from eukaryotes
is:
A. Eukaryotes are always multicellular; prokaryotes are unicellular
B. Eukaryotes have internal organelles; prokaryotes do not
C. Eukaryotic cells are always larger than prokaryotic cells
D. Eukaryotes do not have cell walls; most prokaryotes do
E. Eukaryotic cells have both DNA and RNA; prokaryotic cells possess RNA only
Answer:
1.D
11.A
2.C
12.B
3.A
13.B
4.D
14.B
5.A
15.B
6.C 7.C 8.D 9.C 10.C
Chapter 2: Carbohydrates
1．The correct generic molecular formula for carbohydrates is:
A. (CHnO)2
B. (CHO2)n
C. (CH2O)n
D. (C2HO)n
2．Most carbohydrates are chiral; however, one is not. Which is it?
A. ribose
B. fructose
C. dihydroxyacetone
D. erythrose
E. glucose
F. glyceraldehyde
3．The stereochemical configuration of a sugar (i.e. D- or L-) is defined by
which chiral carbon?
A. The carbon at the center of the sugar
B. The chiral carbon with the lowest number
C. The carbon at the greatest distance from the carbonyl carbon
D. The aldehydic carbon
E. The chiral carbon at the greatest distance from the carbonyl carbon
4．Which of the following is the correct Fischer projection of glucose?
A.
B.
C.
D.
E.
F.
5．Which of the following is the correct Haworth projection of
beta-D-glucopyranose?
A.
B.
C.
D.
E.
F.
6．Pure solutions of a chiral compound, such as a sugar, rotate plane polarized
light either to the left or to the right. This optical rotation can be used to
determine the optical purity of a mixture of enatiomers. If a 1 gm/dL solution of
a mixture of D- and L-glucose at 20 °C has an optical rotation of -12.5°, what is
the composition of the mixture? Pure D-glucose under the same conditions
has a specific rotation of +52.5°.
A. 76.2% L-glucose, 23.8% D-glucose
B. 88.1% L-glucose, 11.9% D-glucose
C. Cannot be determined from the information provided.
D. 61.9% L-glucose, 38.1% D-glucose
7．Which of the following sugars is an epimer of glucose at C-4?
A. mannose
B. ribose
C. galactose
D. fructose
8．These relationship of the following isomers is:
A. diastereomers
B. anomers
C. enantiomers
D. epimers
E. conformers
9．From the following data, select the structure that is least abundant.
Relative amount of tautomeric forms of monosaccharides in water at 20
°C.
relative amount (%)
sugar
pyranose
furanose
alpha-
beta-
alpha-
beta
ribose
20
56
6
18
glucose
36
64
<< 1
<< 1
mannose
67
33
<< 1
<< 1
fructose
3
57
9
31
Ref.: Angew. Chem. 8 (1969) 157-226.
A.
B.
C.
D.
E.
F.
10．Which of the following is the tautomer of ribose found in nucleotides?
A.
B.
C.
D.
11．The specific rotation of pure beta-D-glucose is +18.9°. Calculate the
specific optical rotation of alpha-D-glucose at 20 °C using the data from
Questions 6 and 9.
A. 33.6°
B. 71.4°
C. 112.2°
D. 29.5°
12．At equilibrium, the percentage of alpha-pyranose tautomer of glucose in
solution is almost precisely opposite that of mannose (See Question 9). What
is the reason for this difference?
A. Glucose prefers the furanose tautomer forms
B. Glucose and mannose are diastereomers
C. Mannose is less soluble than glucose in water
D. The C-2 hydroxyl sterically interferes with ring closure.
13．Which of the following is a nonreducing sugar?
A. maltose
B. cellobiose
C. lactose
D. glucose
E. sucrose
Answer:
1.C
2.C
3.E
11.C 12.D 13.E
4.B
5.B
6.D 7.C 8.E 9.F 10.C
Chapter 3: Lipids and Membranes
1．Which of the following lipids contains phosphate?
A. cholesterol
B. cerebroside
C. testosterone
D. diacylglycerol
E. sphingomyelin
F. ceramide
2．What is the correct IUPAC name for the following fatty acid?
A. cis-Δ9,12-hexadecenoate
B. cis,cis-Δ9,12-hexadecadienoate
C. all cis-Δ9,12,15-octadecatrienoate
D. all cis-Δ5,8,11-octadecatrienoate
E. all trans-Δ9,12,15-octadecatrienoate
F. all cis-Δ5,8,11,14-eicosatetraenoate
3．Which of the following statements is not true of fatty acids found in most
mammalian cells?
A. Usually contain 12 - 20 carbons
B. Polyunsaturated fatty acids contain conjugated double bonds
C. Double bonds are found at positions ω-3 or greater
D. All double bonds are in the cis configuration
E. Free fatty acids are ionized at physiological pH
4．Fatty acids are stored in mammals as:
A. free fatty acids
B. triacylglycerol
C. phosphatidylcholine
D. sphingomyelin
E. cholesterol
5．If you were to compare the fatty acid content of triacylglycerols in vegetable oil with those in
butter, what general trends would you expect to find?
A. Butter would contain a higher percentage of more polyunsaturated fatty acids than
vegetable oil
B. Butter would contain a higher percentage of short, polyunsaturated fatty acids than
vegetable oil
C. Butter would contain a lower percentage of polyunsaturated fatty acids than vegetable
oil
D. Butter would contain a higher percentage of arachidonic acid than vegetable oil
E. Butter would contain fatty acids of approximately the same length and degree of
unsaturation as vegetable oil.
6．The product of pancreatic lipase digestion of triacylglycerols is:
A.
B.
C.
D.
E.
7．Which of the following is not a major component of biological membranes?
A. phosphatidylcholine
B. phosphatidylserine
C. sphingomyelin
D. phosphatidylethanolamine
E. cholesterol
F. triacylglycerol
8．You have isolated several unknown phospholipases and find that, when
mixed with human erythrocyte membranes, one of the phospholipases
produces phosphatidate as the primary product. Of which class is this
phospholipase?
A.A1
B.A2
C.B
D.C
E.D
9. Another phospholipase you've isolated releases fatty acids from human erythrocyte membranes.
You find that these fatty acids are enriched in saturated species. Of which class is this
phospholipase?
A.A1
B.A2
C.B
D.C
E.D
10. The metabolic precursor of all sphingolipids:
A. sphingomyelin
B. diacylglycerol
C. ceramide
D. galactocerebroside
E. phosphatidate
11. Of the glycerophospholipids, sphingomyelin is structurally most similar to:
A. phosphatidate
B. phosphatidylcholine
C. phosphatidylethanolamine
D. phosphatidylserine
E. phosphatidylinositol
12. Which of the following sphingolipids would you predict accumulates in
Tay-Sachs disease?
A. lactosylceramides
B. gangliosides
C. thiamine pyrophosphate
D. sphingomyelins
E. ceramides
F. galactosylceramides
13. Which of the following steroids is the most water soluble?
A. cholesterol
B. testosterone
C. ergosterol
D. stigmasterol
E. sodium cholate
F. a cholestryl ester
14. Which of the following classes of lipids is not derived from arachidonic
acid?
A. prostaglandins
B. thromboxanes
C. leukotrienes
D. isoprenoids
E. All of the above are derived from arachidonic acid.
15. Transmembrane lipid asymmetry is maintained in most cells by the action
of:
A. a phospholipid-specific flippase
B. bacteriorhodopsin
C. Na+,K+-ATPase
D. G proteins
E. protein kinase A
16. Which class of membrane proteins can be removed from the membrane by
changing the ionic strength of the solution?
A. integral
B. peripheral
C. fatty acid-anchored
D. prenylated
E. PI glycan-linked
F. All of the above can be removed by changing the ionic strength
17. The Na+,K+-ATPase is a:
A. passive uniporter
B. passive symporter
C. passive antiporter
D. active uniporter
E. active symporter
F. active antiporter
18. The erythrocte membrane contains channels that function to exchange
anions, such as chloride (Cl-) and bicarbonate (HCO3), across the membrane
bilayer. From the following data describe the effect that exogenous sulfate
(SO4-) has on (Cl-) influx in erythroyctes.
A. Sulfate is an activator of the anion channel
B. Sulfate is a non-competitive inhibitor of the anion channel
C. Sulfate is a comptetitive inhibitor of chloride transport
D. Sulfate is an uncompetitive inhibitor of chloride transport
E. Sulfate has no effect on chloride transport
19. What would be the effect of a mutation of a Gα protein such that it no longer
has GTPase activity?
A. The pathway mediated by the G protein would be inactivated
B. The concentration of free Gβγ subunits would decrease
C. The signalling pathway would be constitutively active
D. The percentage of Gα proteins bound to GDP would increase
E. None of the above
20. Caffeine potentiates the activation of the protein kinase A pathway
because:
A. it binds to the regulatory subunit of protein kinase A and promotes dissociation of the
catalytic subunit
B. it activates hormone receptors directly
C. it stimulates the GTPase activity of G proteins
D. it inhibits cAMP phosphodiesterase and prolongs the cAMP signal
E. it binds to target proteins and promotes phosphorylation by protein kinase A
21. Signalling pathways are a balance of positive and negative signals. Cholera toxin, the active
agent of Cholera vibrio causes an increase in protein kinase A activity. Which of the following
statements is consistent with this effect.
A. Cholera toxin binds to, and inhibits, Giα
B. Cholera toxin activates Giα
C. Cholera toxin binds to, and inhibits, Gsα
D. Cholera toxin inhibits adenylate cyclase
E. Cholera toxin binds to the Gβγ subunits and prevents their binding to the Gα subunit
22. Gβγ subunits:
A. bind only to Gsα.
B. bind only to Giα
C. bind only to Gqα.
D. bind to all Gα subtypes
23. Which second messenger are released by activation of receptors coupled
to Gq G-proteins?
A. diacylglycerol
B. IP3
C. Ca2+
D. Only two of the above
E. All of the above
F. None of the above.
24. Which of the following enzymes is involved in the activation of the protein kinase C
signalling pathway
A. Ca2+-ATPase
B. DAG kinase
C. IP3 phosphatase
D. serine/threonine phosphatase
E. Gβγ
F. phospholipase C
25. Mutations in the proteins involved in growth factor signalling are often
associate with cancers. Why?
A. These mutations prevent the receptors from dimerizing, thus induce altered cell growth
B. Mutations to proteins in these pathways result in constitutive, unregulated activation of
the receptor, thus inducing altered cell growth
C. Such mutations affect the ability of the cell to respond to insulin and produce a poor
utilization of glucose
D. Mutations in growth factor receptors inhibit the tyrosine kinase activity of the receptor,
thus result in altered cell growth
Answer:
1.E 2.C 3.B 4.B 5.C
11.B 12.B 13.E 14.D 15.A
21.A 22.D 23.E 24.F 25.B
6.D 7.F 8.E
9.A 10.C
16.B 17.F 18.C 19.C 20.D
Chapter 4: Amino Acids and Primary Structures of Proteins
1. Which of the following depictions of L-threonine is incorrect? [To view
stereo images, use the viewer provided with your textbook.]
A.
B.
C.
D.
E.
F.
2.The correct name for L-isoleucine in the RS nomencalture is:
A. (2R,3R)-isoleucine
B. (2R,3S)-isoleucine
C. (2S,3R)-isoleucine
D. (2S,3S)-isoleucine
E. None of the above.
3. Which of the following amino acids strongly absorbs UV light?
A. Y
B. None of the above
C. W
D. All of the above
E. F
F.
4. The net charge on the amino acid lysine at pH 7.4 is:
A. -2
B. -1
C. +2
D. +1
5. Which of the following amino acids is likely to be found on the surface of a
globular protein?
A. alanine
B. isoleucine
C. serine
D. leucine
E. valine
6. Which of the following amino acids are capable of forming a homodimer in
proteins when oxidized?
A.
B.
C.
D.
E.
7.Of the following tripeptides, which is more likely to be soluble in a non-polar
solvent?
A. ysylglycylserine
B. threonylleucylhistidine
C. leucylalanyltrypthophan
D. valyltryptophanylglutamine
E. glutamylalanylphenylalanine
8. Which of the following is derived from the amino acid glutamate?
A. epinephrine
B. gamma-aminobutyrate
C. triiodothyronine
D. histamine
E. thyroxine
9. Which of the following forms of cysteine predominates at pH 9?
A.
B.
C.
D.
E.
10. The form of aspartate depicted below predominates at which point on the
titration curve?
A.
B.
C.
D.
E.
F.
11. Although protein concentration can be estimated by measuring the absorbance of a protein
solution at 280 nm, this technique does not yield an accurate measure of absolute protein
concentration. Why?
A. The aromatic amino acid content varies from protein to protein
B. Cysteine residues absorb light optimally at this wavelength
C. Most proteins contain strongly attached chromophore molecules, such as hemes, that
absorb light at 280 nm
D. Proteins scatter light optimally at this wavelength, thus interfering with the
concentration measurement
E. Protein solutions refract light optimally at 280 nm, thus interfering with the
measurement
12. Calculate the net charge of the following decapeptide at neutral pH:
MARLYWEQCK
A. 2
B. -1
C. -2
D. 1
Answer:
1.B 2.D 3.D 4.D 5.C
11.A 12.D
Chapter 5:
Chapter 6:
6.D 7.C 8.B 9.C 10.C
The biological Functions of Protein
Secondary, Tertiary, and Quaternary Structure
1．Free rotation about the peptide bond in a protein is restricted primarily
because of:
A. steric interference of neighboring amino acid side chains
B. hydrogen bonding to the amide backbone groups
C. partial double bond character of the peptide bond
D. restrictions caused by local folding patterns
E. partial double bond character of the N-Calpha bond
2．A Ramachandran plot describes, for a particular amino acid, the sterically
permitted angles for:
A. a] rotation about the Calpha-Cbeta bond
B. b] rotation about the Calpha-C bond
C. c] rotation about the N-Calpha bond
D. d] rotation about the Calpha-H bond
E. e] both b] and c]
F. f] both a] and b]
3．Inter-strand hydrogen bonds to the main-chain amide bonds help to stabilize the secondary
structure
A. beta-strands
B. 310 helix
C. 313 helix
D. capping boxes
E. all of the above
4．Proline has a limited number of allowed conformations because
A. it has a bulky side chain
B. it is a cyclic pyrrolidine
C. it is hydrophobic
D. it is a small aliphatic amino acid
E. its side chain is uncharged
5．The number of amino acid residues per turn of an alpha-helix is
A. 1.8
B. 2.4
C. 3.6
D. 4.2
E. 4.8
F. 5.4
6．In an alpha helix, the amide carbonyl oxygen of an amino acid residue n is hyrodrogen bonded
to the amide hydrogen of residue n + _?
A. 2
B. 3
C. 4
D. 5
E. 6
F. 7
7．Which of the following amino acids is least likely to be found in an extended
alpha-helix?
A. valine
B. isoleucine
C. arginine
D. serine
E. asparagine
F. proline
8．Which of the following peptides is likely to form an amphipathic helix?
A. phe-asp-gly-arg-leu-glu-ile-lys-ile-ser-gly
B. phe-leu-ile-ile-gly-asp-arg-glu-lys-ser-gly
C. arg-asp-ser-gly-phe-leu-ile-ile-gly-glu-lys
D. phe-asp-arg-gly-leu-glu-ile-ile-lys-ser-gly
E. phe-gly-leu-ile-asp-arg-glu-lys-ile-ser-gly
9．Isolated beta-strands in proteins are rare primarily because
A. most amino acids prefer the alpha-helix conformation
B. adjacent beta-strands are required to satisfy the hydrogen bond requirement of the
main chain amide bonds
C. polypeptide chains do not prefer to adopt an extended conformation
D. only hydrophobic amino acids are found in beta-strands
E. beta-strands always prefer to be buried in the interior of proteins
10．Antiparallel beta-sheets are often found at the surface of a protein, while parallel beta-sheet
structures are found in the interior of proteins. From this information one can infer that
A. anti-parallel beta sheets are composed of hydrophilic amino acids only
B. parallel beta sheets contain alternating hydrophilic and hydrophobic amino acids
C. every third or fourth amino acid in an antiparallel beta sheet is charged
D. parallel beta sheets are composed of hydrophilic amino acids
E. antiparallel beta sheets are composed of alternating hydrophobic and hydrophilic
amino acids
11．A Greek key is
A. a supersecondary protein structure composed of parallel beta sheets
B. a supersecondary protein structure composed of antiparallel beta sheets
C. a Type I loop
D. a Type II loop
E. the basic structure of a beta barrel
12．What is the force which is primarily responsible for stabilizing the tertiary
structure of globular proteins?
A. ionic interactions
B. hydrogen bonding
C. van der Waals interactions
D. the hydrophobic effect
E. disulfide bonding
13．Which of the following statements about multisubunit globular proteins is incorrect?
A. Oligomers are more stable than subunit monomers
B. Multisubunit proteins are typically regulated by ligand-induced changes in monomer
subunit structure
C. Subunits are typically held together by covalent interactions
D. Multisubunit enzymes often assemble the active site with residues from adjacent
subunits
E. Errors during protein synthesis are minimized by the synthesis of shorter proteins
14．Which of the following proteins stabilize unfolded proteins?
A. protein disulfide isomerase
B. lysyl oxidase
C. lactalbumin
D. peptidyl prolyl isomerase
E. chaperones
15．Which of the following is a representation of a Schiff base?
A.
B.
C.
D.
E.
16．Which of the following statements most accurately describes the
conclusions of Christian Anfinsen's experiment with ribonuclease A?
A. Denaturants, such as urea, are sufficient to completely denature ribonuclease
B. Enzyme activity is preserved even when the protein is denatured
C. The primary amino acid sequence of ribonuclease is the primary determinant of its
three dimensional structure
D. Disulfide bridging only occurs when proteins are properly folded
E. Protein denaturation is rarely reversible
17．The collagen defect present in scurvy is
A. decreased protein stability due to decreased hydroxylation of pro and lys residues
B. substitution of gly for pro and lys residues in the collagen sequence
C. increased formation of Schiff base crossli
D. decreased protein stability due to increased glycosylation
E. conversion of the collagen helix from a right- to a left-handed triple supercoil
18．Substitution of gly in the primary sequence of collagen with almost any other amino acid
results in defective collagen assembly because
A. gly is crosslinked to allysine residues in the mature protein
B. collagen is glycosylated on gly residues
C. the contact points of the triple helix are so close that only the gly sidechain fits well into
the space available.
D. gly forms critical hydrogen bonds with neighboring glycines
E. intrachain hydrogen bonding is dependent on the presence of gly residues
19．Which of the following characteristics is not shared by both hemoglobin and myoglobin?
A. possesses a heme prosthetic group
B. binds O2 reversibly
C. secondary structure is almost completely alpha-helix
D. is a multisubunit protein
E. his residues are involved in O2 binding
20．Molecular oxygen binds to myoglobin between which of the following?
A. his93 and his64
B. phe43 and heme-Fe(II)
C. phe43 and val68
D. his64 and phe43
E. his93 and heme-Fe(II)
21．Which of the following conditions promotes release of oxygen from
hemoglobin?
A. increased pH
B. increased CO2
C. decreased 2,3BPG
D. all of the above
E. none of the above
22．Which of the following has the highest P50?
A. Mb
B. HbF
C. HbA at pH 7.6
D. HbA + 2,3BPG
E. HbA - 2,3BPG
23．When oxygen binds to a subunit of hemoglobin:
A. a] CO2 is displaced from the oxygen binding site
B. b] a large conformational change occurs at the a1b2 interface
C. c] 2,3BPG binds to the core of the hemoglobin tetramer
D. d] the subunit changes from the T to the R conformation
E. b] and d]
24．Complete reduction of the disulfide bonds of immunoglobulin G yields how many different
polypeptide chains?
A. 1
B. 2
C. 3
D. 4
E. 5
F. 6
25．The predominant secondary structural motif in an antibody molecule is:
A. alpha-helix
B. antiparallel beta-sheet
C. parallel beta-sheet
D. alpha-helical coiled coil
E. 4-helix bundle
F. mixed alpha-helix and beta-sheet
Answer:
1.C
11.B
21.B
2.E
12.D
22.D
3.A
4.B
5.C
13.C 14.E 15.B
23.E 24.B 25.B
6.C 7.F 8.D
16.C 17.A 18.C
9.B 10.B
19.D 20.E
Chapter 7: Enzymes
1. The class of enzyme that catalyzes the following reaction is:
A. lyase
B. transferase
C. oxidoreductase
D. iosmerase
E. hydrolase
F. ligase
2. The kinetic order of the reaction catalyzed by adenylate kinase is:
ADP + ADP -> ATP + AMP
A. 1st order
B. 2nd order
C. 3rd order
D. pseudo 2nd order
E. pseudo 1st order
3. An accurate measure of an enzyme concentration can be obtained by measuring catalytic
activity, only when:
A. product formation is slow
B. substrate concentration is saturating
C. enzyme concentration exceeds substrate concentration
D. substrate concentration is limiting
E. None of the above
F. enzyme concentration equals substrate concentration
4. Which of the following is defined as the "turnover number?"
A. kcat
B. (k-1 + kcat)/k1
C. k1
D. k1/k-1
E. k-1
F. kcat/Km
5. When substrate concentration is increased for a simple enzymatic reaction, the reaction order
progresses from first order to zero order with respect to substrate concentration, because
A. Substrate-substrate interactions at high concentrations become strong
B. None of the enzyme is found in the ES complex
C. Significant product formation results in inhibition of the reaction
D. All of the active sites of the enzyme are saturated with substrate at high substrate
concentrations
E. Enzyme-product complexes prevent further binding of more substrate
6. Which of the following assumptions are used in the Briggs-Haldane
derivation of the Michaelis-Menten equation?
A. All of the above were used in deriving the Michaelis-Menten equation
B. The overall rate of the reaction is dependent only on the catalytic rate constant (kcat).
C. At saturating concentrations of substrate, nearly all of the enzyme is found in the ES
complex
D. None of the above assumptions were used in deriving the Michaelis-Menten equation
E. The concentration of the ES complex rapidly reaches a steady state
F. Substrate concentration is greater than enzyme concentration
7. Which of the following statements about the Michaelis constant (Km) is
correct?
A. None of the above are true
B. The Km defines the set point for the concentration of a substrate for a biochemical
reaction in a cell.
C. The Km is the substrate concentration at ½ maximal velocity
D. The Km is a measure of the affinity of the substrate for the enzyme, only if kcat greater
than either k1 or k-1
E. All of the above are true.
8. Measurement of which of the following kinetic parameters requires that
absolute concentration of the enzyme is known?
A. None of the above
B. Vmax
C. Km
D. All of the above.
E. kcat
9. Using the following data for a bisubstrate enyzme, select the most likely
kinetic reaction mechanism:
A. ping-pong
B. Not enough information is provided to determine the mechanism
C. sequential, ordered
D. sequential, random
10. You have obtained the following data for enzyme activity measured in the
presence of an inhibitor, I. Identify the type of inhibition.
A. competitive
B. None of the above.
C. noncompetitive
D. uncompetitive
E. Cannot be determined from the information given
11. You have obtained the following data for enzyme activity measured in the
presence of an inhibitor, I. Identify the type of inhibition.
A. competitive
B. None of the above
C. noncompetitive
D. uncompetitive
E. Cannot determine from the information given
12. Decamethonium has been used during surgery as a neurotransmitter
antagonist to induce paralysis. Once decomethonium administriation is halted
its effects are slowly reversed.
From this information, select the neurotransmitter, whose receptor is the most
likely target for decamethonium.
A.
B.
C.
D.
E.
F.
13. The addition of an compound A to a hypothetical enzyme yields the
following initial velocity curve:
Which of the following statements is true?
A. A is a negative, competitive, allosteric effector
B. A is a competitive inhibitor, but is not an allosteric effector
C. A is a non-competitive inhibitor, but is not an allosteric effector
D. A is a positive allosteric effector
E. A is a negative, non-competitive allosteric effector
14. Which compound would you choose as the best competitive inhibitor of the
hexokinase reaction?
A.
B.
C.
D. None of the above would inhibit the hexokinase reaction
E.
15. You think you may have found a new inhibitor (I) of the HIV protease, so you perform a few
experiments to characterize its behavior. You find that if you add an excess of synthetic substrate
to the protease in the presence of the inhibitor, enzyme actitivity increases but only reaches 50%
of the Vmax observed in the absence of the inhibitor. The affinity of the substrate for the enzyme is
unaffected by the inhibitor. Furthermore, if you treat the enzyme with the inhibitor, then dialyze
the protein, you find that full activity can be restored. What class of inhibitor is I?
A. noncompetitive
B. Cannot be determined from the information given
C. competitive
D. uncompetitiv
E. irreversible
16. From the following data for a hypothetical enzyme, choose the most
effective substrate.
Km
kcat
(micromolar)
-1
(s )
substrate
A. Substrate D
B. Substrate C
C. Susbtrate E
A
0.01
2 x 10-2
B
0.1
4 x 10-4
C
1
2 x 102
D
10
7 x 10-1
E
100
5 x 104
F
1000
2 x 103
D. Substrate F
E. Substrate B
F. Substrate A
17. Phosphorylation is a common means of regulating protein activity. Which
of the following amino acids are typically phosphorylated in proteins regulated
by kinases?
A. threonine
B. serine
C. tyrosine
D. None of the above
E. All of the above
18. Which of the following sets of data results from an allosteric enzyme that is
accurately described by a concerted theory for allostery?
A. Not enough information given to determine
B.
C. None of the above
D.
E.
19. You have isolated a protein that binds to and cleaves negatively charged
lipids. You suspect the critical sequence for lipid binding is:
53
thr-ala-phe-arg-try-met58
To test this hypothesis you decide to perform a site-directed mutagenesis
experiment. Which of the following mutants would you select?
A. 53ala-ala-phe-arg-try-met58
B. 53thr-ala-ala-arg-try-met58
C. 53thr-ala-phe-arg-ala-met58
D. 53thr-ala-phe-arg-try-alat58
E. 53thr-ala-phe-ala-try-met58
20. While studying the following metabolic pathway:
A -> B -> C
You find that after adding A to a cell extract that you can detect C, but not B.
You immediately suspect that your pathway is exhibiting:
A. metabolite channelling
B. sequential kinetics
C. that ADP binds not only to the actpositive allosteric activation
D. regulation by covalent modification
E. cooperativity
21. One of the effects of aspirin is the slowing of blood clotting by inhibiting the
enzyme cycloxygenase in blood platelets. The rate of reversal of the effects of
aspirin parallel the rate of turnover of platelets. This information implies that
aspirin:
A. is an uncompetitive inhibitor of the cyclooxygenase
B. is a competitive inhibitor of the cyclooxygenase
C. is an irreversible inhibitor of the cyclooxygenase
D. regulates the production of platelets
E. is a negative allosteric effector of the cyclooxygenase
22. Allosteric effectors:
A. None of the above
B. typically bind to sites distant from the active site of an enzyme
C. can be very different in structure than the substrates of the enzyme
D. All of the above
E. induce a conformational change in the protein to alter its activity
F. convert the enzyme either to the R or the T state
23. Select the description of a protein demonstrating sequential kinetics that is
not true.
A. In the enzyme complex, monomeric units might be in a mix of R and T states.
B. Once a substrate binds to the R state, all of the monomeric units are "locked" into the R
state
C. The addition of more substrate increases the affinity of the complex for additional
substrate molecules
D. The substrate binds only to the R state
E. The enzyme interconverts between the T and R states in the absence of substrate
24. Which type of reversible enzyme inhibitor binds to both the free enzyme
and the ES complex?
A. noncompetitive
B. Two of the above.
C. competitive
D. None of the above
E. uncompetitive
25. Under which of the following conditions would an enzyme fail to be accurately described by
the Michaelis-Menten equation
A. kcat >> k1 or k-1
B. In the presence of a negative allosteric effector
C. At low concentrations the reaction is first order with respect to substrate concentration
D. None of the above
E. At high concentrations the reaction is zero order with respect to substrate
Answer:
1.B 2.B 3.B 4.A 5.D
11.C 12.B 13.A 14.B 15.A
21.C 22.D 23.A 24.A 25.B
6.A 7.E 8.E
16.C 17.E 18.C
9.A 10.D
19.E 20.A
Chapter 8: Nucleotides and Nucleic Acids
1. Which of the following is the structure of the base 2,6-diaminopurine?
A.
C.
B.
D.
2. Based on the nomenclature given on p. 250, which of the following
structures is pAp?
A.
B.
C.
D.
3. The enzyme polynucleotide phosphorylase can polymerize nucleoside
diphosphates into polynucleotides, a reaction similar to that found on p. 254.
Besides polynucleotides, the other products of the reaction catalyzed by
polynucleotide phosphorylase would be:
A. Pyrophosphate
B. Adenosine monophosphate
C. Triphosphate
D. Monophosphate
4. The reaction catalyzed by polynucleotide phosphorylase is not as energetically favorable in
cells as the reaction catalyzed by DNA or RNA polymerases (i.e., the reaction shown in Figure
9-16). Why is this?
A. The high energy pyrophosphate is further broken down to monophosphates
B. The bond between the a and b phosphates is less activated in nucleoside
diphosphates than in nucleotide triphosphates
C. The polynucleotide phosphorylase enzyme is not as catalytically efficient as a DNA or
RNA polymerase
D. The net change in the charge of the products relative to the substrates is larger for the
polymerization of nucleoside triphosphates
5. Nucleotides serve as both activating groups and 慼 andles?for enzymes.
You can imagine different types of reactions being 慶 oded?for by the different
nucleotides. Based on what you have read, which of the following 慶 odes?is
likely true:
A. Adenosine nucleotides are the only ones used for energetically unfavorable reactions.
B. Cytidine nucleotides are the only ones used for energetically unfavorable reactions
C. Cytidine nucleotides are the only ones used for phospholipid biosynthesis
D. Uridine nucleotides are the only ones used for oligosaccharide biosynthesis
6. The charge on pNpp (nucleoside 5?monophosphate, 3?diphosphate) at
neutral pH is:
A.-4
B.-5
C.-6
D.-7
7. The base hypoxanthine is shown below.
The predominant tautomer of hypoxanthine will look like which of the
following?
A.
B.
C.
D.
8. For the reaction ATP + AMP --> 2 ADP what is the net change in charge
between reactants and products?
A.0
B.1
C.-1
D.-2
9. In the reaction catalyzed by the enzyme adenylate kinase (p. 252), which of
the following shows the change in the charge of the substrates and products?
A. (-1) + (-5) = (-3) + (-3)
B. (-2) + (-4) = (-4) + (-2)
C. (-2) + (-4) = (-3) + (-3)
D. (-1) + (-5) = (-4) + (-2)
10. ADP labeled on the beta phosphate is used in a reaction with nucleoside
diphosphate kinase (pp. 253-254) and GTP. The reaction is allowed to
equilibrate. At the end, label is found in:
A. ADP
B. ADP and enzyme
C. ADP, GTP, and enzyme
D. ADP, ATP, GDP, GTP, and enzyme
11. Which of the following is a tautomer of theophylline (p. 247)?
A.
B.
C.
D.
12. Which of the following bases could not form a Watson-Crick-like pairing (p.
594)?
A. 5-methyl cytosine
B. 7-methyl adenine
C. 1-methyl guanine
D. 3-methyl guanine
13. The nucleoside 8-bromoguanosine is frequently found in the syn
conformation. Why?
A. The bromo group can hydrogen bond to the 5?hydroxyl of the sugar
B. The bromo group can hydrogen bond to the 2?hydroxyl of the sugar.
C. The bromo group alters the tautomer equilibrium so that the lactim form of guanosine
forms a hydrogen bond with the 5?hydroxyl.
D. The bromo group is sterically hindered from being adjacent to the sugar.
14. The proper abbreviation for 5-methyl deoxyuridine diphosphate would be:
A. dUDP
B. dTDP
C. TDP
D. UDP
15. Assume your hand is a ribose ring. Further assume that your thumb
represents the glycosidic bond and that your little (5th) finger represents the
5?hydroxymethyl group, and that these point towards the back of your hand.
The 2?and 3?hydroxyl groups can be represented by your second and third
fingers. To maintain proper conformation, these would point:
A. second finger towards the back of your hand, third finger towards your palm
B. second finger towards your palm, third finger towards the back of your hand
C. second finger towards your palm, third finger towards your palm
D. second finger towards the back of your hand, third finger towards the back of your
hand
16. The drug AZT, azidothymidine, is a potent inhibitor of HIV-1. It is
introduced into replicating viral DNA by viral reverse transcriptase. While the
drug that is administered is not phosphorylated, the active version contains a
5?triphosphate. Where does this 5?triphosphate come from?
A. A viral kinase specifically adds the three phosphates necessary for incorporation
B. An ATP directly donates a triphosphate to the drug
C. The monophosphate is made by thymidine kinase, while the di- and triphosphates are
made by nucleoside monophosphate kinase and nucleoside diphosphate kinase,
respectively
D. Adenylate kinase successively removes the gamma-phosphates from three ATP
molecules and builds up the triphosphate on AZT.
17. Many DNA polymerases can use nucleoside triphosphates that include a
sulfur in place of a non-bridging oxygen on the alpha phosphate. Following
incorporation, the stereochemistry of such thiophosphate nucleosides:
A. is inverted
B. is retained
C. is inverted twice, and hence retained
D. is such that the thiophosphates are not chiral
18. In the reaction described by equation 9-4 (p. 256), CDP-alcohols are
synthesized. Such CDP alcohols serve as intermediates in the synthesis of
phospholipids. The phosphates in CDP alcohols:
A. Come from CTP
B. Come partially from CTP and partially from an alcohol phosphate
C. Come from an alcohol phosphate
D. Come from pyrophosphate
19. In different organisms, CDP-alcohols are made in different ways. In
organisms that utilize an alcohol rather than an alcohol phosphate as a
substrate for the synthesis of the CDP-alcohol:
A. The phosphates in the CDP-alcohol come from the beta and gamma phosphates of
CTP.
B. The phosphates in the CDP-alcohol come from the alpha and beta phosphates of CTP
C. The phosphates in the CDP-alcohol come from the gamma phosphate of ATP and the
gamma phosphate of CTP
D. The phosphates in the CDP-alcohol comes from the beta and gamma phosphates of
ATP
20. CDP labeled on the beta phosphate is fed to an organism. When a
phospholipid such as phosphatidyl choline is synthesized via the intermediates
shown in Figure 9-18:
A. The label ends up in CDP
B. The label ends up in CMP
C. The label ends up in the phospholipid
D. The label ends up in pyrophosphate
21. Now, assume that CDP-diacylglycerol is made as in Figure 9-18. If it is
made from CTP labeled on the alpha phosphate:
A. The label ends up in phosphatidyl serine
B. The label ends up in pyrophosphate
C. The label ends up in CDP
D. The label ends up in CMP
22. In the synthesis of cyclic ADP-ribose (Figure 9-22), the leaving group
would have been:
A. Ribose
B. Adenosine
C. Adenine
D. Nicotinamide
23. For adenosine, the positions on the ring that are hydrogen bond acceptors
are:
A. 1,3
B. 1,3,7
C. 1,3,6,7
D. 3,7
24. If ApppppA is an inhibitor of adenylate kinase (p. 253), then which of the
following might be expected to be an inhibitor of guanylate kinase (p. 252):
A. ApppG
B. AppppG
C. ApppppG
D. AppppppG
25. Based on what you know of magnesium chelation to nucleotides (Figure
9-13, p. 251), how many different ways would there be to bind a single
magnesium ion to ApppppA?
A.2
B.3
C.4
D.5
Answer:
1.B
2.D
3.D
4.A
5.C
11.A 12.C 13.D 14.B 15.C
21.D 22.D 23.B 24.C 25.C
6.B
7.B 8.A
16.C 17.A 18.B
9.C 10.A
19.B 20.D