ACS Final Review Flashcards
1
Q
Which of these statements about hydrogen bonds is not true?
A. Hydrogen bonds account for the anomalously high boiling point of water.
B. In liquid water, the average water molecule forms hydrogen bonds with three to four other water
molecules.
C. Individual hydrogen bonds are much weaker than covalent bonds.
D. Individual hydrogen bonds in liquid water exist for many seconds and sometimes for minutes.
E. The strength of a hydrogen bond depends on the linearity of the three atoms involved in the bond.
A
D. Individual hydrogen bonds in liquid water exist for many seconds and sometimes for minutes.
2
Q
The pH of a solution of 1 M HCl is:
A. 0
B. 0.1
C. 1
D. 10
A
A. 0
3
Q
The aqueous solution with the highest pH is:
A. 1 M HCl.
B. 1 M NH3 (pKa = 9.25).
C. 0.5 M NaHCO3 (pKa = 3.77).
D. 0.1 M NaOH.
E. 0.001 M NaOH.
A
D. 0.1 M NaOH.
4
Q
Phosphoric acid is tribasic, with pKa’s of 2.14, 6.86, and 12.4. The ionic form that predominates at
pH 3.2 is:
A. H3PO4.
B. H2PO4–.
C. HPO42–.
D. PO43–.
E. none of the above
A
B. H2PO4–
5
Q
The enzyme fumarase catalyzes the reversible hydration of fumaric acid to l-malate, but it will not catalyze the hydration of maleic acid, the cis isomer of fumaric acid. This is an example of:
A. biological activity.
B. chiral activity.
C. racemization.
D. stereoisomerization.
E. stereospecificity
A
E. stereospecificity
6
Q
Which of the following statements about buffers is true?
A. A buffer composed of a weak acid of pKa = 5 is stronger at pH 4 than at pH 6.
B. At pH values lower than the pKa, the salt concentration is higher than that of the acid.
C. The pH of a buffered solution remains constant no matter how much acid or base is added to the
solution.
D. The strongest buffers are those composed of strong acids and strong bases.
E. When pH = pKa, the weak acid and salt concentrations in a buffer are equal
A
E. When pH = pKa, the weak acid and salt concentrations in a buffer are equal
7
Q
Of the 20 standard amino acids, only ___________ is not optically active. The reason is that its side chain ___________.
A. alanine; is a simple methyl group
B. glycine; is a hydrogen atom
C. glycine; is unbranched
D. lysine; contains only nitrogen
E. proline; forms a covalent bond with the amino group
A
B. glycine; is a hydrogen atom
8
Q
Two amino acids of the standard 20 contain sulfur atoms. They are:
A. cysteine and serine.
B. cysteine and threonine.
C. methionine and cysteine
D. methionine and serine
E. threonine and serine.
A
C. methionine and cysteine
9
Q
For amino acids with neutral R groups, at any pH below the pI of the amino acid, the population of amino acids in solution will have:
A. a net negative charge.
B. a net positive charge.
C. no charged groups.
D. no net charge.
E. positive and negative charges in equal concentration.
A
B. a net positive charge
10
Q
The formation of a peptide bond between two amino acids is an example of a(n) ______________ reaction.
A. cleavage
B. condensation
C. group transfer
D. isomerization
E. oxidation reduction
A
B. condensation
11
Q
The peptide alanylglutamylglycylalanylleucine has:
A. a disulfide bridge.
B. five peptide bonds.
C. four peptide bonds.
D. no free carboxyl group.
E. two free amino groups.
A
C. four peptide bonds.
12
Q
At the isoelectric pH of a tetrapeptide:
A. only the amino and carboxyl termini contribute charge.
B. the amino and carboxyl termini are not charged.
C. the total net charge is zero.
D. there are four ionic charges.
E. two internal amino acids of the tetrapeptide cannot have ionizable R groups.
A
C. the total net charge is zero
13
Q
A compound has a pKa of 7.4. To 100 mL of a 1.0 M solution of this compound at pH 8.0 is
added 30 mL of 1.0 M hydrochloric acid. The resulting solution is pH:
A. 6.5
B. 6.8
C. 7.2
D. 7.4
E. 7.5
A
D. 7.4
14
Q
The average molecular weight of the 20 standard amino acids is 138, but biochemists use 110 when estimating the number of amino acids in a protein of known molecular weight. Why?
A. The number 110 is based on the fact that the average molecular weight of a protein is 110,000
with an average of 1,000 amino acids.
B. The number 110 reflects the higher proportion of small amino acids in proteins, as well as the
loss of water when the peptide bond forms.
C. The number 110 reflects the number of amino acids found in the typical small protein, and only
small proteins have their molecular weight estimated this way.
D. The number 110 takes into account the relatively small size of nonstandard amino acids.
E. The number 138 represents the molecular weight of conjugated amino acids.
A
B. The number 110 reflects the higher proportion of small amino acids in proteins, as well as the loss
of water when the peptide bond forms
15
Q
Which of the following is correct with respect to the amino acid composition of proteins?
A. Larger proteins have a more uniform distribution of amino acids than smaller proteins.
B. Proteins contain at least one each of the 20 different standard amino acids.
C. Proteins with different functions usually differ significantly in their amino acid composition.
D. Proteins with the same molecular weight have the same amino acid composition.
E. The average molecular weight of an amino acid in a protein increases with the size of the protein.
A
C. Proteins with different functions usually differ significantly in their amino acid composition
16
Q
Roughly how many amino acids are there in one turn of an α helix?
A. 1
B. 2.8
C. 3.6
D. 4.2
A
C. 3.6
17
Q
Thr and/or Leu residues tend to disrupt an α helix when they occur next to each other in a protein
because:
A. an amino acids like Thr is highly hydrophobic.
B. covalent interactions may occur between the Thr side chains.
C. electrostatic repulsion occurs between the Thr side chains.
D. steric hindrance occurs between the bulky Thr side chains.
E. the R group of Thr can form a hydrogen bond.
A
D. steric hindrance occurs between the bulky Thr side chains
18
Q
In an α helix, the R groups on the amino acid residues:
A. alternate between the outside and the inside of the helix.
B. are found on the outside of the helix spiral.
C. cause only right-handed helices to form.
D. generate the hydrogen bonds that form the helix.
E. stack within the interior of the helix.
A
B. are found on the outside of the helix spiral.
19
Q
In a mixture of the five proteins listed below, which should elute second in size-exclusion (gel-
filtration) chromatography?
A. immunoglobulin G Mr = 145,000
B. ribonuclease A Mr = 13,700
C. RNA polymerase Mr = 450,000
D. serum albumin Mr = 68,500
A
A. immunoglobulin G Mr = 145,000
20
Q
By adding SDS (sodium dodecyl sulfate) during the electrophoresis of proteins, it is possible to:
A. determine a protein’s isoelectric point.
B. determine the amino acid composition of the protein.
C. preserve a protein’s native structure and biological activity.
D. separate proteins exclusively on the basis of molecular weight.
A
D. separate proteins exclusively on the basis of molecular weight
21
Q
Amino acids are ampholytes because they can function as either a(n):
A. acid or a base.
B. neutral molecule or an ion.
C. polar or a nonpolar molecule.
D. standard or a nonstandard monomer in proteins.
E. transparent or a light-absorbing compound.
A
A. acid or a base
22
Q
The functional differences, as well as differences in three-dimensional structures, between two
different enzymes from E. coli result directly from their different:
A. affinities for ATP.
B. amino acid sequences.
C. roles in DNA metabolism.
D. roles in the metabolism of E. coli.
E. secondary structures.
A
B. amino acid sequences.
23
Q
Determining the precise arrangement of atoms within a large protein is possible only through the
use of:
A. electron microscopy.
B. light microscopy.
C. Ramachandran plots.
D. x-ray diffraction
A
D. x-ray diffraction
24
Q
The α-keratin chains indicated by the diagram below have undergone one chemical step. To alter
the shape of the α-keratin chains—as in hair waving—what subsequent steps are required?
A. Chemical reduction and then shape remodeling
B. Shape remodeling and then chemical oxidation
C. Shape remodeling and then chemical reduction
A
B. Shape remodeling and then chemical oxidation
25
Experiments on denaturation and renaturation after the reduction and reoxidation of the —S—
S— bonds in the enzyme ribonuclease (RNase) have shown that:
A. folding of denatured RNase into the native, active conformation, requires the input of energy in
the form of heat.
B. native ribonuclease does not have a unique secondary and tertiary structure.
C. the completely unfolded enzyme, with all —S—S— bonds broken, is still enzymatically active.
D. the enzyme, dissolved in water, is thermodynamically stable relative to the mixture of amino acids whose residues are contained in RNase.
E. the primary sequence of RNase is sufficient to determine its specific secondary and tertiary
structure.
E. the primary sequence of RNase is sufficient to determine its specific secondary and tertiary
structure.
26
Which of the following is least likely to result in protein denaturation?
A. Altering net charge by changing pH
B. Changing the salt concentration
C. Disruption of weak interactions by boiling
D. Exposure to detergents
E. Mixing with organic solvents such as acetone
B. Changing the salt concentration
27
Amino acid residues commonly found in the middle of β turn are:
A. Ala and Gly.
B. hydrophobic.
C. Pro and Gly.
D. those with ionized R-groups.
E. two Cys
C. Pro and Gly.
28
The major reason that antiparallel β-stranded protein structures are more stable than parallel β-
stranded structures is that the latter:
A. are in a slightly less extended configuration than antiparallel strands.
B. do not have as many disulfide crosslinks between adjacent strands.
C. have fewer lateral hydrogen bonds than antiparallel strands.
D. have weaker hydrogen bonds laterally between adjacent strands.
D. have weaker hydrogen bonds laterally between adjacent strands
29
A sequence of amino acids in a certain protein is found to be -Ser-Gly-Pro-Gly-. The sequence is
most probably part of a(n):
A. antiparallel β sheet.
B. parallel β sheet.
C. α helix.
D. α sheet.
E. β turn.
E. β turn.
30
Which of the following statements is false?
A. Collagen is a protein in which the polypeptides are mainly in the α-helix conformation.
B. Disulfide linkages are important for keratin structure.
C. Gly residues are particularly abundant in collagen.
D. Silk fibroin is a protein in which the polypeptide is almost entirely in the β conformation.
E. α-keratin is a protein in which the polypeptides are mainly in the α-helix conformation.
A. Collagen is a protein in which the polypeptides are mainly in the α-helix conformation
31
Proteins are classified within families or superfamilies based on similarities in:
A. evolutionary origin.
B. physico-chemical properties.
C. structure and/or function.
D. subcellular location.
E. subunit structure
C. structure and/or function
32
Which of the following statements concerning the process of spontaneous folding of proteins is
false?
A. It may be an essentially random process.
B. It may be defective in some human diseases.
C. It may involve a gradually decreasing range of conformational species.
D. It may involve initial formation of a highly compact state.
E. It may involve initial formation of local secondary structure
A. It may be an essentially random process
33
Titration of valine by a strong base, for example NaOH, reveals two pK’s. The titration reaction
occurring at pK2 (pK2 = 9.62) is:
A) —COOH + OH− → —COO− + H2O.
B) —COOH + —NH2 → —COO− + —NH2+.
C) —COO− + —NH2+ → —COOH + —NH2.
D) —NH3+ + OH− → —NH2 + H2O.
E) —NH2 + OH− → —NH− + H2O
D) —NH3+ + OH− → —NH2 + H2O
34
In a conjugated protein, a prosthetic group is:
A. a fibrous region of a globular protein.
B. a nonidentical subunit of a protein with many identical subunits.
C. a part of the protein that is not composed of amino acids.
D. a subunit of an oligomeric protein.
E. synonymous with “protomer.”
C. a part of the protein that is not composed of amino acids
35
The interactions of ligands with proteins:
A. are relatively nonspecific.
B. are relatively rare in biological systems.
C. are usually irreversible.
D. are usually transient.
E. usually result in the inactivation of the proteins
D. are usually transient
36
Myoglobin and the subunits of hemoglobin have:
A. no obvious structural relationship.
B. very different primary and tertiary structures.
C. very similar primary and tertiary structures.
D. very similar primary structures, but different tertiary structures.
E. very similar tertiary structures, but different primary structures
D. very similar primary structures, but different tertiary structures
BUT: This is actually an incomplete, not totally correct answer. They share a core fold which contains high
sequence similarity. Then the extra sequence varies. So similar primary sequence, similar tertiary
structure, but myoglobin is monomeric and Hb is tetrameric so very different quaternary structures.
37
Which of the following generalizations concerning motor proteins is correct?
A. They convert chemical energy into kinetic energy.
B. They convert chemical energy into potential energy.
C. They convert kinetic energy into chemical energy.
D. They convert kinetic energy into rotational energy.
E. They convert potential energy into chemical energy.
A. They convert chemical energy into kinetic energy
38
An allosteric interaction between a ligand and a protein is one in which:
A. binding of a molecule to a binding site affects binding of additional molecules to the same site.
B. binding of a molecule to a binding site affects binding properties of another site on the protein.
C. binding of the ligand to the protein is covalent.
D. multiple molecules of the same ligand can bind to the same binding site.
E. two different ligands can bind to the same binding site.
B. binding of a molecule to a binding site affects binding properties of another site on the protein.
39
When oxygen binds to a heme-containing protein, the two open coordination bonds of Fe2+ are
occupied by:
A. one O atom and one amino acid atom.
B. one O2 molecule and one amino acid atom.
C. one O2 molecule and one heme atom.
D. two O atoms.
B. one O2 molecule and one amino acid atom
40
In hemoglobin, the transition from T state to R state (low to high affinity) is triggered by:
A. Fe2+ binding.
B. heme binding.
C. oxygen binding.
D. subunit association.
E. subunit dissociation
C. oxygen binding
41
Carbon monoxide (CO) is toxic to humans because:
A. it binds to myoglobin and causes it to denature.
B. it is rapidly converted to toxic CO2.
C. it binds to the globin portion of hemoglobin and prevents the binding of O2.
D. it binds to the Fe in hemoglobin and prevents the binding of O2.
E. it binds to the heme portion of hemoglobin and causes heme to unbind from hemoglobin
D. it binds to the Fe in hemoglobin and prevents the binding of O2
42
The amino acid substitution of Val for Glu in Hemoglobin S results in aggregation of the protein
because of ___________ interactions between molecules.
A. covalent
B. disulfide
C. hydrogen bonding
D. hydrophobic
E. ionic
D. hydrophobic
43
An individual molecular structure within an antigen to which an individual antibody binds is as
a(n):
A. antigen.
B. epitope.
C. Fab region.
D. Fc region
E. MHC site
B. epitope.
44
Even when a gene is available and its sequence of nucleotides is known, chemical studies of the
protein are still required to determine:
A. molecular weight of the protein.
B. the amino-terminal amino acid.
C. the location of disulfide bonds.
D. the number of amino acids in the protein.
E. whether the protein has the amino acid methionine in its sequence
C. the location of disulfide bonds
45
The term “proteome” has been used to describe:
A. regions (domains) within proteins.
B. regularities in protein structures.
C. the complement of proteins encoded by an organism’s DNA.
D. the structure of a protein-synthesizing ribosome.
E. the tertiary structure of a protein
C. the complement of proteins encoded by an organism’s DNA
46
Which of the following parts of the IgG molecule are not involved in binding to an antigen?
A. Fab
B. Fc
C. Heavy chain
D. Light chain
E. Variable domain
B. Fc
47
Which immunoglobulin is involved in allergic reactions?
A. IgE
B. IgA
C. IgG
D. IgM
A. IgE
48
Which one of the following is not among the six internationally accepted classes of enzymes?
A. Hydrolases
B. Ligases
C. Oxidoreductases
D. Polymerases
D. Polymerases
49
Enzymes are potent catalysts because they:
A. are consumed in the reactions they catalyze.
B. are very specific and can prevent the conversion of products back to substrates.
C. drive reactions to completion while other catalysts drive reactions to equilibrium.
D. increase the equilibrium constants for the reactions they catalyze.
E. lower the activation energy for the reactions they catalyze
E. lower the activation energy for the reactions they catalyze.
50
Which one of the following statements is true of enzyme catalysts?
A. Their catalytic activity is independent of pH.
B. They are generally equally active on D and L isomers of a given substrate.
C. They can increase the equilibrium constant for a given reaction by a thousand fold or more.
D. They can increase the reaction rate for a given reaction by a thousand fold or more.
E. To be effective, they must be present at the same concentration as their substrate.
D. They can increase the reaction rate for a given reaction by a thousand fold or more.
51
Which of the following statements is false?
A. A reaction may not occur at a detectable rate even though it has a favorable equilibrium.
B. After a reaction, the enzyme involved becomes available to catalyze the reaction again.
C. For S → P, a catalyst shifts the reaction equilibrium to the right.
D. Lowering the temperature of a reaction will lower the reaction rate.
E. Substrate binds to an enzyme's active site
C. For S → P, a catalyst shifts the reaction equilibrium to the right
52
The concept of “induced fit” refers to the fact that:
A. enzyme specificity is induced by enzyme-substrate binding.
B. enzyme-substrate binding induces an increase in the reaction entropy, thereby catalyzing the reaction.
C. enzyme-substrate binding induces movement along the reaction coordinate to the transition state.
D. substrate binding may induce a conformational change in the enzyme, which then brings catalytic
groups into proper orientation.
D. substrate binding may induce a conformational change in the enzyme, which then brings catalytic
groups into proper orientation
53
The steady state assumption, as applied to enzyme kinetics, implies:
A. the enzyme is regulated.
B. the ES complex is formed and broken down at equivalent rates.
C. the Km is equivalent to the cellular substrate concentration.
B. the ES complex is formed and broken down at equivalent rates
54
Which of these statements about enzyme-catalyzed reactions is false?
A. At saturating levels of substrate, the rate of an enzyme-catalyzed reaction is proportional to the
enzyme concentration.
B. If enough substrate is added, the normal Vmax of a reaction can be attained even in the presence of a
competitive inhibitor.
C. The rate of a reaction decreases steadily with time as substrate is depleted.
D. The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but
the equilibrium constant is more favorable in the enzyme-catalyzed reaction.
E. The Michaelis-Menten constant Km equals the [S] at which V = 1/2 Vmax.
D. The activation energy for the catalyzed reaction is the same as for the uncatalyzed reaction, but
the equilibrium constant is more favorable in the enzyme-catalyzed reaction
55
Which of the following statements about a plot of V0 vs. [S] for an enzyme that follows
Michaelis-Menten kinetics is false?
A. As [S] increases, the initial velocity of reaction V0 also increases.
B. At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km.
C. Km is the [S] at which V0 = 1/2 Vmax.
D. The shape of the curve is a hyperbola.
B. At very high [S], the velocity curve becomes a horizontal line that intersects the y-axis at Km
56
Lineweaver-Burk plot is used to:
A. determine the equilibrium constant for an enzymatic reaction.
B. extrapolate for the value of reaction rate at infinite enzyme concentration.
C. illustrate the effect of temperature on an enzymatic reaction.
D. solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration.
E. solve, graphically, for the ratio of products to reactants for any starting substrate concentration.
D. solve, graphically, for the rate of an enzymatic reaction at infinite substrate concentration
57
In competitive inhibition, an inhibitor:
A. binds at several different sites on an enzyme.
B. binds covalently to the enzyme.
C. binds only to the ES complex.
D. binds reversibly at the active site.
lowers the characteristic Vmax of the enzyme.
D. binds reversibly at the active site.
58
Vmax for an enzyme-catalyzed reaction:
A. generally increases when pH increases.
B. increases in the presence of a competitive inhibitor.
C. is limited only by the amount of substrate supplied.
D. is twice the rate observed when the concentration of substrate is equal to the Km.
E. is unchanged in the presence of a uncompetitive inhibitor
D. is twice the rate observed when the concentration of substrate is equal to the Km
59
In a plot of l/V against 1/[S] for an enzyme-catalyzed reaction, the presence of a competitive
inhibitor will alter the:
A. curvature of the plot.
B. intercept on the l/[S] axis.
C. intercept on the l/V axis.
D. pK of the plot.
B. intercept on the l/[S] axis.
60
Phenyl-methane-sulfonyl-fluoride (PMSF) inactivates serine proteases by binding covalently to
the catalytic serine residue at the active site; this enzyme-inhibitor bond is not cleaved by the
enzyme. This is an example of what kind of inhibition?
A. irreversible
B. competitive
C. non-competitive
D. mixed
E. pH inhibition
A. irreversible
61
A good transition-state analog:
A. binds covalently to the enzyme.
B. binds to the enzyme more tightly than the substrate.
C. binds very weakly to the enzyme.
D. is too unstable to isolate.
E. must be almost identical to the substrate.
B. binds to the enzyme more tightly than the substrate
62
The double-reciprocal transformation of the Michaelis-Menten equation, also called the
Lineweaver-Burk plot, is given by
1/V0 = Km /(Vmax[S]) + 1/Vmax.
To determine Km from a double-reciprocal plot, you would:
A. multiply the reciprocal of the x-axis intercept by −1.
B. multiply the reciprocal of the y-axis intercept by −1.
C. take the reciprocal of the x-axis intercept.
D. take the reciprocal of the y-axis intercept.
E. take the x-axis intercept where V0 = 1/2 Vmax
A. multiply the reciprocal of the x-axis intercept by −1
63
A small molecule that decreases the activity of an enzyme by binding to a site other than the
catalytic site is termed a(n):
A. allosteric inhibitor.
B. alternative inhibitor.
C. competitive inhibitor.
D. stereospecific agent.
E. transition-state analog
A. allosteric inhibitor
64
A zymogen is:
A. A transition-state analog
B. An enzyme class
C. An enzyme that needs to be activated via cleavage
D. An enzyme without its cofactor
C. An enzyme that needs to be activated via cleavage
65
How is trypsinogen converted to trypsin?
A. A protein kinase-catalyzed phosphorylation converts trypsinogen to trypsin.
B. An increase in Ca2+ concentration promotes the conversion.
C. Proteolysis of trypsinogen forms trypsin.
D. Trypsinogen dimers bind an allosteric modulator, cAMP, causing dissociation into active trypsin
monomers.
E. Two inactive trypsinogen dimers pair to form an active trypsin tetramer.
C. Proteolysis of trypsinogen forms trypsin
66
The difference between a ribonucleotide and a deoxyribonucleotide is:
A. a deoxyribonucleotide has an —H instead of an —OH at C-2.
B. a deoxyribonucleotide has α configuration; ribonucleotide has the β configuration at C-1.
C. a ribonucleotide has an extra —OH at C-4.
D. a ribonucleotide has more structural flexibility than deoxyribonucleotide.
E. a ribonucleotide is a pyranose, deoxyribonucleotide is a furanose
A. a deoxyribonucleotide has an —H instead of an —OH at C-2.
67
Which one of the following is true of the pentoses found in nucleic acids?
A. C-5 and C-1 of the pentose are joined to phosphate groups.
B. C-5 of the pentose is joined to a nitrogenous base, and C-1 to a phosphate group.
C. The bond that joins nitrogenous bases to pentoses is an O-glycosidic bond.
D. The pentoses are always in the β-furanose forms.
E. The straight-chain and ring forms undergo constant interconversion
D. The pentoses are always in the β-furanose forms.
68
The phosphodiester bonds that link adjacent nucleotides in both RNA and DNA:
A. always link A with T and G with C.
B. are susceptible to alkaline hydrolysis.
C. are uncharged at neutral pH.
D. form between the planar rings of adjacent bases.
E. join the 3' hydroxyl of one nucleotide to the 5' hydroxyl of the next
E. join the 3' hydroxyl of one nucleotide to the 5' hydroxyl of the next
69
In the Watson-Crick model for the DNA double helix (B form) the A–T and G–C base pairs
share which one of the following properties?
A. The distance between the two glycosidic (base-sugar) bonds is the same in both base pairs, within
a few tenths of an angstrom.
B. The molecular weights of the two base pairs are identical.
C. The number of hydrogen bonds formed between the two bases of the base pair is the same.
D. The plane of neither base pair is perpendicular to the axis of the helix.
E. The proton-binding groups in both base pairs are in their charged or ionized form
A. The distance between the two glycosidic (base-sugar) bonds is the same in both base pairs, within
a few tenths of an angstrom.
70
Which of the following monosaccharides is not an aldose?
A. erythrose
B. fructose
C. glucose
D. glyceraldehyde
E. ribose
B. fructose
71
When two carbohydrates are epimers:
A. one is a pyranose, the other a furanose.
B. one is an aldose, the other a ketose.
C. they differ in length by one carbon.
D. they differ only in the configuration around one carbon atom.
E. they rotate plane-polarized light in the same direction
D. they differ only in the configuration around one carbon atom.
72
Which of the following pairs is interconverted in the process of mutarotation?
A. D-glucose and D-fructose
B. D-glucose and D-galactose
C. D-glucose and D-glucosamine
D. D-glucose and L-glucose
E. α-D-glucose and β-D-glucose
E. α-D-glucose and β-D-glucose
73
When the linear form of glucose cyclizes, the product is a(n):
A. anhydride.
B. glycoside.
C. hemiacetal.
D. lactone.
E. oligosaccharide
C. hemiacetal.
74
Starch and glycogen are both polymers of:
A. fructose.
B. glucose1-phosphate.
C. sucrose.
D. α-D-glucose.
E. β-D-glucose
D. α-D-glucose.
75
B-form DNA in vivo is a ________-handed helix, _____ Å in diameter, with a rise of ____ Å per
base pair.
A. left; 20; 3.9
B. right; 18; 3.4
C. right; 18; 3.6
D. right; 20; 3.4
E. right; 23; 2.6
D. right; 20; 3.4
76
Which of the following is not a reducing sugar?
A. Fructose
B. Glucose
C. Glyceraldehyde
D. Ribose
E. Sucrose
E. Sucrose
77
From the abbreviated name of the compound Gal(β1 → 4)Glc, we know that:
A. C-4 of glucose is joined to C-1 of galactose by a glycosidic bond.
B. the compound is a D-enantiomer.
C. the galactose residue is at the reducing end.
D. the glucose is in its pyranose form.
E. the glucose residue is the β anomer
A. C-4 of glucose is joined to C-1 of galactose by a glycosidic bond.
78
Which of the following statements about starch and glycogen is false?
A. Amylose is unbranched; amylopectin and glycogen contain many (α1 → 6) branches.
B. Both are homopolymers of glucose.
C. Both serve primarily as structural elements in cell walls.
D. Both starch and glycogen are stored intracellularly as insoluble granules.
E. Glycogen is more extensively branched than starch.
C. Both serve primarily as structural elements in cell walls
79
Which of the following is a heteropolysaccharide?
A. Cellulose
B. Chitin
C. Glycogen
D. Hyaluronate
E. Starch
D. Hyaluronate
80
Which of the following is a dominant feature of the outer membrane of the cell wall of gram
negative bacteria?
A. Amylose
B. Cellulose
C. Glycoproteins
D. Lipopolysaccharides
E. Lipoproteins
D. Lipopolysaccharides
81
In glycoproteins, the carbohydrate moiety is always attached through the amino acid residues:
A. asparagine, serine, or threonine.
B. aspartate or glutamate.
C. glutamine or arginine.
D. glycine, alanine, or aspartate.
E. tryptophan, aspartate, or cysteine
A. asparagine, serine, or threonine
82
83
The experimental method that generates many copies of a gene for sequencing or cloning is:
A. Edman degradation
B. Sanger sequencing
C. PCR (polymerase chain reaction)
D. SDS-PAGE
E. RNA-Se
C. PCR (polymerase chain reaction)
84
Glucose transport into erythrocytes is an example of:
A. active transport.
B. antiport.
C. electrogenic uniport
D. facilitated diffusion.
E. symport.
D. facilitated diffusion.
85
For the process of solute transport, the constant Kt is:
A. analogous to Ka for ionization of a weak acid.
B. analogous to Km for an enzyme-catalyzed reaction.
C. analogous to Vmax for an enzyme reaction
D. proportional to the number of molecules of glucose transporter per cell.
E. the maximum rate of glucose transport.
B. analogous to Km for an enzyme-catalyzed reaction.
86
A ligand-gated ion channel (such as the nicotinic acetylcholine receptor) is:
A. a charged lipid in the membrane bilayer that allows ions to pass through.
B. a membrane protein that permits a ligand to pass through the membrane only when opened by the
appropriate ion.
C. a membrane protein that permits an ion to pass through the membrane only when opened by the
appropriate ligand.
D. a molecule that binds to the membrane thereby allowing ions to pass through.
E. always requires a second ligand to close the channel once it is opened.
C. a membrane protein that permits an ion to pass through the membrane only when opened by the
appropriate ligand.
87
Which of the following statements concerning receptor enzymes is correct?
A. They are not usually membrane-associated proteins.
B. They contain an enzyme activity that acts upon a cytosolic substrate.
C. They contain an enzyme activity that acts upon the extracellular ligand.
D. They have a ligand-binding site on the cytosolic side of the membrane.
E. They have an active site on the extracellular side of the membrane
B. They contain an enzyme activity that acts upon a cytosolic substrate.
88
Protein kinase A (PKA) is:
A. activated by covalent binding of cyclic AMP.
B. affected by cyclic AMP only under unusual circumstances.
C. allosterically activated by cyclic AMP.
D. competitively inhibited by cyclic AMP.
E. noncompetitively inhibited by cyclic AMP
C. allosterically activated by cyclic AMP.
89
Which of the following is not involved in signal transduction by the β-adrenergic receptor
pathway?
A. ATP
B. Cyclic AMP
C. Cyclic GMP
D. GTP
E. All of the above are involved.
C. Cyclic GMP
90
91
The ion channel that opens in response to acetylcholine is an example of a ____________ signal
transduction system.
A. G protein
B. ligand-gated
C. receptor-enzyme
D. serpentine receptor
E. voltage-gated
B. ligand-gated
92
The G-protein involved in visual signal transduction is:
A. a leukotriene.
B. transducin.
C. arrestin.
D. rhodopsin.
E. a GTP receptor
B. transducin.
93
When a mixture of 3-phosphoglycerate and 2-phosphoglycerate is incubated at 25 °C with phosphoglycerate mutase until equilibrium is reached, the final mixture contains six times as much 2-phosphoglycerate as 3 phosphoglycerate. Which one of the following statements is most nearly correct, when applied to the reaction as written? (R = 8.315 J/mol·K; T = 298 K)
3-Phosphoglycerate → 2-phosphoglycerate
A. ΔG'° is –4.44 kJ/mol.
B. ΔG'° is zero.
C. ΔG'°is +12.7 kJ/mol.
D. ΔG'°is incalculably large and positive.
E. ΔG'° cannot be calculated from the information given
A. ΔG'° is –4.44 kJ/mol.
94
When a mixture of glucose 6-phosphate and fructose 6-phosphate is incubated with the enzyme phosphohexose isomerase (which catalyzes the interconversion of these two compounds) until
equilibrium is reached, the final mixture contains twice as much glucose 6-phosphate as fructose
6-phosphate. Which one of the following statements is best applied to this reaction outlined
below? (R = 8.315 J/mol·K; T = 298 K)
Glucose 6-phosphate → fructose 6-phosphate
A. ΔG'° is incalculably large and negative.
B. ΔG'° is –1.72 kJ/mol.
C. ΔG'° is zero.
D. ΔG'° is +1.72 kJ/mol.
D. ΔG'° is +1.72 kJ/mol.
95
Hydrolysis of 1 M glucose 6-phosphate catalyzed by glucose 6-phosphatase is 99% complete at
equilibrium (i.e., only 1% of the substrate remains). Which of the following statements is most
nearly correct? (R = 8.315 J/mol·K; T = 298 K)
A. ΔG'° = –11 kJ/mol
B. ΔG'° = –5 kJ/mol
C. ΔG'° = 0 kJ/mol
D. ΔG'° = +11 kJ/mol
A. ΔG'° = –11 kJ/mol
96
The reaction A + B → C has a ΔG'° of –20 kJ/mol at 25° C. Starting under standard conditions,
one can predict that:
A. at equilibrium, the concentration of B will exceed the concentration of A.
B. at equilibrium, the concentration of C will be less than the concentration of A.
C. at equilibrium, the concentration of C will be much greater than the concentration of A or B.
D. C will rapidly break down to A + B
C. at equilibrium, the concentration of C will be much greater than the concentration of A or B.
97
98
During glycolysis, glucose 1-phosphate is converted to fructose 6-phosphate in two successive
reactions:
Glucose 1-phosphate → glucose 6-phosphate ΔG'° = –7.1 kJ/mol
Glucose 6-phosphate → fructose 6-phosphate ΔG'° = +1.7 kJ/mol
ΔG'° for the overall reaction is:
A. –8.8 kJ/mol.
B. –7.1 kJ/mol.
C. –5.4 kJ/mol.
D. +5.4 kJ/mol.
E. +8.8 kJ/mol.
C. –5.4 kJ/mol
99
The standard free-energy changes for the reactions below are given.
Phosphocreatine → creatine + PiΔG'° = –43.0 kJ/mol
ATP → ADP + Pi ΔG'° = –30.5 kJ/mol
What is the overall ΔG'° for the following reaction?
Phosphocreatine + ADP → creatine + ATP
A. –73.5 kJ/mol
B. –12.5 kJ/mol
C. +12.5 kJ/mol
D. +73.5 kJ/mol
E. ΔG'° cannot be calculated without Keq'
B. –12.5 kJ/mol
100
The reaction ATP -->ADP + Pi is an example of a reaction.
A. homolytic cleavage
B. internal rearrangement
C. free radical
D. group transfer
E. oxidation/reduction
D. group transfer
101
All of the following contribute to the large, negative, free-energy change upon hydrolysis of
“high-energy” compounds except:
A. electrostatic repulsion in the reactant.
B. low activation energy of forward reaction.
C. stabilization of products by extra resonance forms.
D. stabilization of products by ionization.
E. stabilization of products by solvation.
B. low activation energy of forward reaction.
102
The hydrolysis of ATP has a large negative ΔG'°; nevertheless it is stable in solution due to:
A. entropy stabilization.
B. ionization of the phosphates.
C. resonance stabilization.
D. the hydrolysis reaction being endergonic.
E. the hydrolysis reaction having a large activation energy
E. the hydrolysis reaction having a large activation energy
103
Biological oxidation-reduction reactions always involve:
A. direct participation of oxygen.
B. formation of water.
C. mitochondria.
D. transfer of electron(s).
E. transfer of hydrogens
D. transfer of electron(s)
104
The standard reduction potentials (E'°) for the following half reactions are given.
Fumarate + 2H+ + 2e– → succinate E'° = +0.031 V
FAD + 2H+ + 2e– → FADH2 E'° = –0.219 V
If you mixed succinate, fumarate, FAD, and FADH2 together, all at l M concentrations and in the
presence of succinate dehydrogenase, which of the following would happen initially?
A. Fumarate and succinate would become oxidized; FAD and FADH2 would become reduced.
B. Fumarate would become reduced, FADH2 would become oxidized.
C. No reaction would occur because all reactants and products are already at their standard
concentrations.
D. Succinate would become oxidized, FAD would become reduced.
E. Succinate would become oxidized, FADH2 would be unchanged because it is a cofactor
B. Fumarate would become reduced, FADH2 would become oxidized.
105
E'° of the NAD+/NADH half reaction is –0.32 V. The E'° of the oxaloacetate/malate half reaction
is –0.175 V. When the concentrations of NAD+, NADH, oxaloacetate, and malate are all 10–5 M,
the “spontaneous” reaction is:
A. Malate + NAD+ → oxaloacetate + NADH + H+.
B. Malate + NADH + H+ → oxaloacetate + NAD+.
C. NAD+ + NADH + H+ → malate + oxaloacetate.
D. NAD+ + oxaloacetate → NADH + H+ + malate.
E. Oxaloacetate + NADH + H+ → malate + NAD+
E. Oxaloacetate + NADH + H+ → malate + NAD+
106
During strenuous exercise, the NADH formed in the glyceraldehyde 3-phosphate dehydrogenase
reaction in skeletal muscle must be reoxidized to NAD+ if glycolysis is to continue. The most
important reaction involved in the reoxidation of NADH is:
A. dihydroxyacetone phosphate → glycerol 3-phosphate
B. glucose 6-phosphate → fructose 6-phosphate
C. isocitrate → α-ketoglutarate
D. oxaloacetate → malate
E. pyruvate → lactate
E. pyruvate → lactate
107
The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all
of the following except:
A. ATP synthesis.
B. catalysis by phosphoglycerate kinase.
C. oxidation of NADH to NAD+.
D. the formation of 1,3-bisphosphoglycerate.
E. utilization of Pi.
C. oxidation of NADH to NAD+.
108
Which of the following is a cofactor in the reaction catalyzed by glyceraldehyde 3-phosphate
dehydrogenase?
A. ATP
B. Cu2+
C. heme
D. NAD+
D. NAD+
109
The first reaction in glycolysis that results in the formation of an energy-rich compound (i.e., a
compound whose hydrolysis has a highly negative ΔG'°) is catalyzed by:
A. glyceraldehyde 3-phosphate dehydrogenase.
B. hexokinase.
C. phosphofructokinase-1.
D. phosphoglycerate kinase.
E. triose phosphate isomerase
A. glyceraldehyde 3-phosphate dehydrogenase.
110
Glycogen is converted to monosaccharide units by:
A. glucokinase.
B. glucose-6-phosphatase
C. glycogen phosphorylase.
D. glycogen synthase.
E. glycogenase
C. glycogen phosphorylase
111
An enzyme used in both glycolysis and gluconeogenesis is:
A. 3-phosphoglycerate kinase.
B. glucose 6-phosphatase.
C. hexokinase.
D. phosphofructokinase-1.
E. pyruvate kinase
A. 3-phosphoglycerate kinase.
112
The main function of the pentose phosphate pathway is to:
A. give the cell an alternative pathway should glycolysis fail.
B. provide a mechanism for the utilization of the carbon skeletons of excess amino acids.
C. supply energy.
D. supply NADH.
E. supply pentoses and NADPH
E. supply pentoses and NADPH
113
Which of these cofactors participates directly in most of the oxidation-reduction reactions in the
fermentation of glucose to lactate?
A. ADP
B. ATP
C. FAD/FADH2
D. Glyceraldehyde 3-phosphate
E. NAD+/NADH
E. NAD+/NADH
114
The steps of glycolysis between glyceraldehyde 3-phosphate and 3-phosphoglycerate involve all
of the following except:
A. ATP synthesis.
B. catalysis by phosphoglycerate kinase.
C. oxidation of NADH to NAD+.
D. the formation of 1,3-bisphosphoglycerate.
E. utilization of Pi.
C. oxidation of NADH to NAD+
115
Glycogen is converted to monosaccharide units by:
A. glucokinase.
B. glucose-6-phosphatase
C. glycogen phosphorylase.
D. glycogen synthase.
E. glycogenase.
C. glycogen phosphorylase
116
Which of the following statements is incorrect?
A. Aerobically, oxidative decarboxylation of pyruvate forms acetate that enters the citric acid cycle.
B. In anaerobic muscle, pyruvate is converted to lactate.
C. In yeast growing anaerobically, pyruvate is converted to ethanol.
D. Reduction of pyruvate to lactate regenerates a cofactor essential for glycolysis.
E. Under anaerobic conditions pyruvate does not form because glycolysis does not occur
E. Under anaerobic conditions pyruvate does not form because glycolysis does not occur
117
An enzyme used in both glycolysis and gluconeogenesis is:
A. 3-phosphoglycerate kinase.
B. glucose 6-phosphatase.
C. hexokinase.
D. phosphofructokinase-1.
E. pyruvate kinase
A. 3-phosphoglycerate kinase
118
In humans, gluconeogenesis:
A. can result in the conversion of protein into blood glucose.
B. helps to reduce blood glucose after a carbohydrate-rich meal.
C. is activated by the hormone insulin
D. is essential in the conversion of fatty acids to glucose.
E. requires the enzyme hexokinase
A. can result in the conversion of protein into blood glucose
119
The metabolic function of the pentose phosphate pathway is:
A. act as a source of ADP biosynthesis.
B. generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.
C. participate in oxidation-reduction reactions during the formation of H2O.
D. provide intermediates for the citric acid cycle.
E. synthesize phosphorus pentoxide
B. generate NADPH and pentoses for the biosynthesis of fatty acids and nucleic acids.
120
Which one of the following types of mechanisms is not known to play a role in the reversible
alteration of enzyme activity?
A. Activation by cleavage of an inactive zymogen
B. Allosteric response to a regulatory molecule
C. Alteration of the synthesis or degradation rate of an enzyme
D. Covalent modification of the enzyme
E. Interactions between catalytic and regulatory subunits
A. Activation by cleavage of an inactive zymogen
121
Gluconeogenesis must use “bypass reactions” to circumvent three reactions in the glycolytic
pathway that are highly exergonic and essentially irreversible. Reactions carried out by which
three of the enzymes listed must be bypassed in the gluconeogenic pathway?
1. Hexokinase
2. Phosphoglycerate kinase
3. Phosphofructokinase-1
4. Pyruvate kinase
5. Triosephosphate isomerase
A. 1, 2, 3
B. 1, 2, 4
C. 1, 4, 5
D. 1, 3, 4
E. 2, 3, 4
D. 1, 3, 4
122
Glycogen phosphorylase a can be inhibited at an allosteric site by:
A. AMP.
B. calcium.
C. glucagon.
D. glucose.
D. glucose.
123
There is reciprocal regulation of glycolytic and gluconeogenic reactions interconverting fructose-
6-phosphate and fructose-1,6-bisphosphate. Which one of the following statements about this
regulation is not correct?
A. Fructose-2,6-bisphosphate activates phosphofructokinase-1.
B. Fructose-2,6-bisphosphate inhibits fructose-1,6-bisphosphatase.
C. The fructose-1,6-bisphosphatase reaction is exergonic.
D. The phosphofructokinase-1 reaction is endergonic.
E. This regulation allows control of the direction of net metabolite flow through the pathway
D. The phosphofructokinase-1 reaction is endergonic
124
Which of the following statements about gluconeogenesis in animal cells is true?
A. A rise in the cellular level of fructose-2,6-bisphosphate stimulates the rate of gluconeogenesis.
B. An animal fed a large excess of fat in the diet will convert any fat not needed for energy production into glycogen to be stored for later use.
C. The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is not catalyzed by
phosphofructokinase-1, the enzyme involved in glycolysis.
D. The conversion of glucose 6-phosphate to glucose is catalyzed by hexokinase, the same enzyme
involved in glycolysis.
E. The conversion of phosphoenol pyruvate to 2-phosphoglycerate occurs in two steps, including a
carboxylation.
C. The conversion of fructose 1,6-bisphosphate to fructose 6-phosphate is not catalyzed by
phosphofructokinase-1, the enzyme involved in glycolysis.
125
Which of the following is not true of the reaction catalyzed by the pyruvate dehydrogenase
complex?
A. Biotin participates in the decarboxylation.
B. Both NAD+ and a flavin nucleotide act as electron carriers.
C. The reaction occurs in the mitochondrial matrix.
D. The substrate is held by the lipoyl-lysine “swinging arm.”
E. Two different cofactors containing —SH groups participate
A. Biotin participates in the decarboxylation
126
Malonate is a competitive inhibitor of succinate dehydrogenase. If malonate is added to a mitochondrial preparation that is oxidizing pyruvate as a substrate, which of the following compounds would you expect to decrease in concentration?
A. Citrate
B. Fumarate
C. Isocitrate
D. Succinate
B. Fumarate
127
Which of the following is not an intermediate of the citric acid cycle?
A. Acetyl-coA
B. Citrate
C. Oxaloacetate
D. Succinyl-coA
A. Acetyl-coA
128
Which one of the following enzymatic activities would be decreased by thiamine deficiency?
A. α-Ketoglutarate dehydrogenase complex
B. Isocitrate dehydrogenase
C. Malate dehydrogenase
D. Succinate dehydrogenase
A. α-Ketoglutarate dehydrogenase complex
129
The reaction of the citric acid cycle that produces an ATP equivalent (in the form of GTP) by
substrate level phosphorylation is the conversion of:
A. fumarate to malate.
B. malate to oxaloacetate.
C. succinate to fumarate.
D. succinyl-CoA to succinate
D. succinyl-CoA to succinate
130
For the following reaction, ΔG'° = 29.7 kJ/mol.
L-Malate + NAD+ → oxaloacetate + NADH + H+
The reaction as written:
A. can never occur in a cell.
B. can only occur in a cell if it is coupled to another reaction for which ΔG'° is positive.
C. can only occur in a cell in which NADH is converted to NAD+ by electron transport.
D. may occur in cells at certain concentrations of substrate and product.
E. would always proceed at a very slow rate
D. may occur in cells at certain concentrations of substrate and product.
131
The standard reduction potentials (E'°) for the following half reactions are given.
Fumarate + 2H+ + 2e– → succinate E'° = +0.031 V
FAD + 2H+ + 2e– → FADH2 E'° = –0.219 V
If succinate, fumarate, FAD, and FADH2, all at l M concentrations, were mixed together in the
presence of succinate dehydrogenase, which of the following would happen initially?
A. Fumarate and succinate would become oxidized; FAD and FADH2 would become reduced.
B. Fumarate would become reduced; FADH2 would become oxidized.
C. No reaction would occur because all reactants and products are already at their standard
concentrations.
D. Succinate would become oxidized; FAD would become reduced.
E. Succinate would become oxidized; FADH2 would be unchanged because it is a cofactor, not a
substrate
B. Fumarate would become reduced; FADH2 would become oxidized.
132
Intermediates in the citric acid cycle are used as precursors in the biosynthesis of:
A. amino acids
B. nucleotides
C. fatty acids
D. sterols
E. all of the above
E. all of the above
