Protein Structure, Protein Metabolism and Nucleic Acid Metabolism Flashcards
The sequence of monomers in any polymer is this type of
structure:
A. primary structure
B. secondary structure
C. tertiary structure
D. quaternary structure
E. All of these
primary structure
Hydrogen bonds are most important in this type of structure in
proteins:
A. primary structure
B. secondary structure
C. tertiary structure
D. quaternary structure
E. All of these
secondary structure
The overall folding of a single protein subunit is called:
A. primary structure
B. secondary structure
C. tertiary structure
D. quaternary structure
E. All of these
tertiary structure
The location of prosthetic groups is shown in this level of
structure:
A. primary structure
B. secondary structure
C. tertiary structure
D. quaternary structure
E. All of these
C. tertiary structure
Structures which repeat over and over in secondary structure
are called:
A. primary structure
B. domain
C. supersecondary structure
D. prosthetic group
E. All of these
C. supersecondary structure
Covalent bonds are important in all these structures, except:
A. primary structure
B. secondary structure
C. tertiary structure
D. quaternary structure
E. All of these
D. quaternary structure
Disulfide bonds are most important in this type of structure:
A. primary structure
B. secondary structure
C. tertiary structure
D. quaternary structure
E. All of these
C. tertiary structure
Which of the following forces are involved in maintaining the
primary structure of a protein?
A. covalent bonds
B. hydrogen bonds
C. ionic interactions
D. hydrophobic interactions
covalent bonds
A single amino substitution can give rise to a malfunctioning
protein.
A. True
B. False
B. False
Assuming the oligopeptide ALPHAHELICKS forms one continuous a-helix, the carbonyl oxygen of the glutamic acid residue
is hydrogen bonded to the amide nitrogen of
A. leucine.
B. isoleucine.
C. cysteine.
D. lysine.
E. serine.
C. cysteine.
What happens when a protein is denatured?
A. Its secondary structure is disrupted but its primary structure
remains intact.
B. Its primary structure is disrupted but its secondary structure
remains intact.
C. It is broken apart into its constituent amino acids.
D. It becomes all a-helix.
A. Its secondary structure is disrupted but its primary structure
remains intact.
Which of the following best defines a domain?
A. A supersecondary region, often shared by proteins, that has a
specific function.
B. A repetitive supersecondary structure.
C. A double-layered arrangement formed so that the polar groups
face the aqueous environment, while the nonpolar regions are
kept away from the aqueous environment.
D. An unfolded region of a protein.
a supersecondary region, often shared by proteins, that has a
specific function
Which of the following amino acids is unlikely to be found in
an a-helix due to its cyclic structure?
A. phenylalanine
B. tryptophan
C. proline
D. lysine
C. proline
Which of the following statements regarding hydrogen bonding
in secondary structures is true?
A. Both a-helices and b-sheets only use intrachain hydrogen
bonds.
B. Both a-helices and b-sheets only use interchain hydrogen
bonds.
C. a-helices only use intrachain hydrogen bonds and b-sheets can
use either intrachain or interchain hydrogen bonds.
D. a-helices can use either intrachain or interchain hydrogen
bonds and b-sheets only use interchain hydrogen bonds.
C. a-helices only use intrachain hydrogen bonds and b-sheets can
use either intrachain or interchain hydrogen bonds.
Which of the following factors tend to destabilize a-helices?
A. clusters of amino acids with bulky R-groups
B. clusters of amino acids with similarly charged R-groups
C. Both of these.
D. Neither of these
both of these
Which of the following best describes the structure of colla
gen?
A. It is composed of a single a-helix.
B. It is a double helix.
C. It is a triple helix
D. It is composed primarily of b-sheet.
its a triple helix
Which of the following is true?
A. The peptide bonds in the b-sheet are extended.
B. The peptide bonds in the a-helix coil back on themselves.
C. Both a-helices and b-sheets can be found as part of tertiary
structure.
D. All of these
all of these
Which of the following is often found connecting the strands of
an antiparallel b-sheet?
A. b-bulge
B. reverse turn
C. a-helix
D. prosthetic group
reverse turn
Which of the following best describes a motif?
A. a repetitive supersecondary structure
B. a common nonrepetitive irregularity found in antiparallel
b-sheets
C. a protein conformation with biological activity
D. a group of atoms other than an amino acid
a repetitive supersecondary structure
In the b-pleated sheet conformation
A. there are hydrogen bonds perpendicular to the direction of the
polypeptide chain.
B. the polypeptide chain is almost fully extended.
C. the polypeptide chains may be hydrogen bonded together in a
parallel or antiparallel orientation.
D. all of these
all of these
Which of the following is the most common function for fibrous
proteins?
A. enzymes
B. structural roles.
C. carrier molecules.
D. enzymes and carrier molecules.
E. All of these.
B. structural roles.
In the a-helix
A. there are no hydrogen bonds
B. the peptide chain is fully extended
C. the peptide chain bends back on itself
D. there are hydrogen bonds parallel to the helix axis
D. there are hydrogen bonds parallel to the helix axis
Which one is not an example of supersecondary structure?
A. the pyrrole ring
B. the Greek key
C. the b-meander
D. the b-barrel
A. the pyrrole ring
Which of the following is true?
A. The collagen helix and the a-helix are the only types of helices
in proteins.
B. Globular proteins tend to be water soluble
C. Globular and fibrous are examples of secondary structure
D. All of these
B. Globular proteins tend to be water soluble
As an animal ages, the amount of cross-linking of collagen in
tissue
A. tends to decrease.
B. tends to increase.
C. tends to remain unchanged.
tends to increase
Vitamin C (ascorbic acid) prevents scurvy because
A. it is involved in the formation of the proper b-sheet structure of
collagen.
B. it is involved in the metabolism of heme used in hemoglobin.
C. it encourages the formation of disulfide linkages in collagen.
D. it is an unusual amino acid found in the primary structure of
collagen.
E. it is used to hydroxylate prolines in the primary structure of
collagen.
it is used to hydroxylate prolines in the primary structure of colla
gen
The following is true about the hydroxyproline in collagen:
A. Hydroxyproline is incorporated into the chain during polymer
ization of amino acids.
B. Vitamin C is necessary for the synthesis of hydroxyproline.
C. Hydroxyproline is important in holding the 3 strands of collagen
together.
D. Hydroxyproline requires Vitamin C for its synthesis and it holds
the collagen helix together.
E. All of these.
hydroxyproline requires vitamin C for its synthesis and it holds the
collagen helix together
Fibrous proteins
A. are always composed of helical structures.
B. are always composed of b-sheets.
C. can be composed of either helical or b-sheet structures.
C. can be composed of either helical or b-sheet structures.
The protein myoglobin
A. contains a high degree of b-pleated sheet structure
B. carries oxygen in the bloodstream
C. contains no histidine
D. contains a heme group
contains a heme group
Generally speaking, this type of protein is water-soluble:
A. Fibrous.
B. Globular.
C. Both fibrous and globular proteins are usually water-soluble.
D. Neither fibrous nor globular proteins are usually water-soluble.
E. You cannot generalize about the solubility of fibrous or globular
proteins.
globular
Domains are
A. independently folded regions of proteins
B. the a-helical portions of proteins
C. the b-pleated regions of proteins
D. all of the above
independently folded regions of proteins
Two amino acids frequently found in reverse turns are
A. tyrosine and tryptophan
B. serine and threonine
C. glycine and proline
D. leucine and isoleucine
C. glycine and proline
Which of the following amino acid residues would most likely
be found in the interior of a globular protein?
A. glutamic acid
B. lysine
C. leucine
D. serine
C. leucine
Disulfide bonds in proteins occur between the side chains of
which of the following amino acid residues?
A. glutamine
B. lysine
C. cysteine
D. methionine
C. cysteine
X-ray crystallography is used to determine protein structure
because
A. it can be done on dilute solutions
B. it requires no calculations
C. the positions of all atoms can be found by this method
D. all of these
C. the positions of all atoms can be found by this method
The structure of myoglobin consists
A. almost entirely of a-helices.
B. almost entirely of b-sheets.
C. of a mixture of a-helices and b-sheets.
D. of a unique secondary motif that is neither a-helix nor b-sheet.
A. almost entirely of a-helices.
The tertiary structure of a protein is usually a result of which
of the following interactions?
A. intramolecular hydrogen bonding
B. electrostatic interactions
C. hydrophobic interactions
D. all of these
D. all of these
Heme would best be described as a
A. motif.
B. domain.
C. prosthetic group.
D. helix.
prosthetic group
Why does myoglobin have a histidine that prevents both O2
and CO from binding perpendicularly to the heme plane?
A. This increases myoglobin’s affinity for O2.
B. This increases myoglobin’s affinity for CO.
C. This lessens the difference in myoglobin’s affinity for CO versus
O2.
D. This prevents the iron of the heme from being oxidized.
C. This lessens the difference in myoglobin’s affinity for CO versus O2.
In what oxidation state must the iron atom be for heme to bind
oxygen?
A. 0, Fe(0)
B. 1+, Fe(I)
C. 2+, Fe(II)
D. 3+, Fe(III)
E. There is no required oxidation state for the iron.
C. 2+, Fe(II)
Which of the following is not true?
A. The heme group of myoglobin is held in place only through
non-covalent bonding.
B. The F8 histidine is important to the function of myoglobin
C. The E7 histidine is important to the function of myoglobin
D. Myoglobin and hemoglobin differ only in one amino acid
D. Myoglobin and hemoglobin differ only in one amino acid
Which of the following can result in protein denaturation?
A. heat
B. extremes of pH
C. detergents
D. all of the above
D. all of the above
The following bond forces are important in tertiary structure:
A. Disulfide bonds
B. Hydrogen bonds
C. Hydrophobic attraction
D. Both hydrogen bonds and hydrophobic attraction.
E. All of these are important in tertiary structure
E. All of these are important in tertiary structure
Quaternary structure is associated with
A. the overall shape of the polypeptide chain
B. the sum of secondary and tertiary interactions
C. simple proteins with only one subunit
D. the relative orientation of one polypeptide to another polypeptide in a multisubunit protein
D. the relative orientation of one polypeptide to another polypeptide in a multisubunit protein
Which of the following forces are involved in maintaining the
quaternary structure of a protein?
A. hydrogen bonds
B. ionic interactions
C. hydrophobic interactions
D. All of these
D. All of these
The following bond forces are important in quaternary struc
ture:
A. Disulfide bonds
B. Hydrogen bonds
C. Hydrophobic attraction
D. Both hydrogen bonds and hydrophobic attraction.
E. All of these are important in quaternary structure.
D. Both hydrogen bonds and hydrophobic attraction.
Under normal circumstances:
A. Adult Hb binds to oxygen more tightly than Mb binds.
B. Fetal Hb binds oxygen more tightly than adult Hb.
C. Adult Hb binds oxygen more tightly than either fetal Hb or Mb
binds.
D. Mb has the lowest affinity for oxygen of the 3.
E. More than one of these statements is correct.
B. Fetal Hb binds oxygen more tightly than adult Hb.
Which of the following statements regarding hemoglobin (Hb)
and myoglobin (Mb) is true?
A. Mb transports oxygen while Hb stores it.
B. Mb has quaternary structure but Hb does not.
C. Mb displays simple kinetics of binding while Hb displays cooperativity.
D. Mb binds Fe(II) while Hb binds heme.
C. Mb displays simple kinetics of binding while Hb displays cooperativity.
Which of the following is not a characteristic of hemoglobin?
A. It contains two different types of subunits .
B. It contains a prosthetic group.
C. It is an allosteric enzyme.
D. It transports oxygen.
E. All of these statements are true for Hb.
C. It is an allosteric enzyme.
The Bohr effect for oxygen binding states that
A. Mb binds oxygen more tightly than Hb.
B. Hb will bind oxygen very tightly when the CO2 concentration is
high.
C. as the pH goes down, Hb binds oxygen less tightly.
D. Hb’s ability to bind oxygen increases with higher oxygen con
centration.
C. as the pH goes down, Hb binds oxygen less tightly.
In allosteric interactions
A. proteins that consist of a single polypeptide chain form aggre
gates.
B. disulfide bonds are broken.
C. changes that take place in one site of a protein cause changes
at a distant site.
D. metal ions always bind to the protein.
C. changes that take place in one site of a protein cause changes
at a distant site.
Hemoglobin differs from myoglobin because
A. it does not have a heme group.
B. it is a tetramer, whereas myoglobin is a single polypeptide chain.
C. it does not contain any helical regions.
D. it contains more b-pleated sheet structure.
B. it is a tetramer, whereas myoglobin is a single polypeptide chain.
Which of the following best describes what happens when
hemoglobin binds bisphosphoglyceric acid (BPG)?
A. Binding of BPG leads to tighter binding of oxygen.
B. Binding of BPG allows maternal (adult) Hb to bind oxygen more
tightly than fetal Hb.
C. Binding of BPG causes oxygen to dissociate from Hb.
D. Binding of BPG causes the subunits of hemoglobin to separate.
C. Binding of BPG causes oxygen to dissociate from Hb.
The binding of oxygen to hemoglobin differs from the oxy
gen-binding behavior of myoglobin because
A. oxygen binding to hemoglobin is cooperative.
B. oxygen binding to myoglobin is cooperative.
C. hemoglobin is not an allosteric protein.
D. the oxygen-binding curve of hemoglobin is hyperbolic.
A. oxygen binding to hemoglobin is cooperative.
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 unchanged
C. is decreased by the presence of H+ and CO2
The affinity of fetal hemoglobin for oxygen
A. has not been 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
C. is lower than that of maternal hemoglobin
Variations in the structure of hemoglobin
A. do not always have an adverse effect on health
B. can alter the binding of heme to the protein
C. can occur on the surface of the protein
D. all of these
all of these
In sickle-cell anemia hemoglobin
A. the four subunits of hemoglobin dissociate from one another
B. the heme group is lost from all subunits
C. the iron is in the Fe(III) form rather than the normal Fe(II)
D. groups of hemoglobin molecules aggregate with each other
D. groups of hemoglobin molecules aggregate with each other
Which of the following proteins is not homologous with the
others?
A. myoglogin
B. a-chain of hemoglobin
C. b-chain of hemoglobin
D. collagen
D. collagen
What is the major force that drives nonpolar substances out
of aqueous solution?
A. Increased enthalpy of hydrophobic bonds formed between
solute molecules.
B. Decreased entropy of newly organized solute molecules.
C. Increased entropy of newly organized solute molecules.
D. Increased enthalpy of H-bonds in the solvent water.
E. Increased entropy of solvent water molecules.
E. Increased entropy of solvent water molecules.
Hydrophobic interactions may occur between the R groups of
which of the following amino acids?
A. tyrosine and glycine
B. arginine and histidine
C. phenylalanine and tryptophan
D. valine and asparagine
phenylalanine and tryptophan
The information needed for the structure of a protein is contained in
A. amino acid composition
B. primary structure
C. secondary structure
D. tertiary structure
B. primary structure
Incorrect protein folding resulting in exposure of hydrophobic
regions can result in
A. aggregation.
B. homology.
C. liposomes.
D. the Bohr effect.
A. aggregation.
Proteins that aid in the correct and timely folding of other
proteins are called
A. motifs.
B. chaperones.
C. liposomes.
D. cooperative.
B. chaperones.
The oxygen binding curve of which of the following is the
closest to that of myoglobin?
A. hemoglobin at pH 6.8
B. hemoglobin that lacks BPG
C. maternal hemoglobin
D. fetal hemoglobin
B. hemoglobin that lacks BPG
The following amino acid causes a kink or bend in the a-helix.
A. Ala
B. Glu
C. Lys
D. Pro
E. Trp
D. Pro
Cys-Ala-Gly-Arg-Gln-Met
The amino terminal amino acid is ___
Cys
Cys-Ala-Gly-Arg-Gln-Met
The carboxyl terminal end is ___
Met
Cys-Ala-Gly-Arg-Gln-Met
The overall, net ionic charge on this peptide at pH=7 would be
+1
In nitrogen fixation, the chemical change is
a. NH4+ to NO2−
b. NO3− to NH4+
c. N2 to NH4+ or NH3
d. NO2− to N2
e. none of these
c. N2 to NH4+ or NH3
Nitrification is the conversion of
a. nitrogen gas to nitrate.
b. nitrogen gas to ammonia.
c. nitrate to ammonia.
d. nitrate to nitrogen gas.
e. ammonia to nitrogen gas.
c. nitrate to ammonia.
Denitrification is carried out by
a. animals.
b. green plants.
c. soil bacteria.
d. all of the above.
e. none of these
c. soil bacteria.
Which of the following is NOT an interconversion of nitrogen performed by living organisms?
a. Fixation of atmospheric nitrogen into ammonia.
b. Fixation of atmospheric nitrogen into nitrate.
c. Nitrification of soil nitrate into ammonia
d. Denitrification of nitrogen oxides to gaseous nitrogen.
e. All of these are common bioconversions in the nitrogen cycle.
e. All of these are common bioconversions in the nitrogen cycle.
The nitrogen-fixing enzyme system, nitrogenase, is found exclusively in
a. plants
b. bacteria
c. some viruses
d. eukaryotic organisms
e. mammals
b. bacteria
How many ATP are required for the production of two ammonia molecules (NH3) from one nitrogen molecule (N2)?
a. 2ATP.
b. 4ATP.
c. 8ATP.
d. 16ATP.
e. 32ATP.
d. 16ATP.
Which of the following is not a component of the nitrogenase complex?
a. a molybdenum complex
b. a nonheme iron-sulfur protein(Feprotein)
c. ferredoxin
d. pyridoxal phosphate
d. pyridoxal phosphate
How many electrons are required for the reduction of one nitrogen molecule (N2) to two molecules of ammonia (NH3) and molecule of hydrogen (H2)?
a. 2 electrons.
b. 4 electrons.
c. 6 electrons.
d. 8 electrons.
e. 12 electrons
d. 8 electrons.
Which of the following is not true regarding ammonia and fertilizers?
a. Ammonia gas is seldom an effective plant fertilizer, since it is usually consumed by
the bacteria in the soil.
b. Many fertilizers are made from ammonia synthesized by the Haber process
c. Researchers are looking for ways to incorporate the genes for nitrogenase into crop
plants so that not as much fertilizer is needed
d. Both ammonium and nitrate ions are frequently used in fertilizers
b. Many fertilizers are made from ammonia synthesized by the Haber process
While the reduction of nitrogen to ammonia in plants follows the same net chemical reaction,
the source of electrons for the process varies from plant to plant.
a. True
b. False
b. False
Nitrogenase uses which of the following cofactors?
a. molybdenum-iron-sulfur complex
b. biotin
c. pyridoxal phosphate
d. thiamine pyrophosphate
e. none of these
a. molybdenum-iron-sulfur complex
Nitrogen fixation in legumes may use as much as half of the ATP made in the plant.
a. True
b. False
a. True
Glycine, alanine, serine, histidine, tryptophan, CTP, AMP, and carbamoyl-phosphate all have
what in common?
a. They are all inhibitors of glutamine synthase
b. They are all amino acids
c. They are all cofactors in transamination reactions
d. They are activators of the urea cycle
a. They are all inhibitors of glutamine synthase
Glutamine synthetase is subject to feedback inhibition by which of the following chemicals?
a. histidine
b. carbamoyl phosphate
c. cytidine triphosphate
(CTP)
d. All of these
d. All of these
A characteristic feature of feedback inhibition is that
a. it is wasteful of energy and reducing power in anabolic pathways
b. it leads to buildup of the end products of anabolic pathways
c. it seldom occurs in the metabolism of compounds of nitrogen
d. it commonly appears in biosynthesis of amino acids
e. it always involves the inhibition of the first step of a pathway
d. it commonly appears in biosynthesis of amino acids
The conversion of α-ketoglutarate to glutamate is
a. a transamination.
b. a reductive amination.
c. an amidation.
d. an oxidation.
e. an isomerization
b. a reductive amination.
The conversion of glutamate to glutamine is catalyzed by glutamine synthetase and requires
ATP.
a. True
b. False
a. True
The synthesis of amino acids occurs in about 5 or 6 related families of amino acids.
a. True
b. False
a. True
Pyridoxal phosphate forms a Schiff base with amino groups in transaminase reactions.
a. True
b. False
a. True
A coenzyme frequently encountered in transamination reactions is
a. tetrahydrofolate.
b. pyridoxal phosphate.
c. thiamine pyrophosphate.
d. biotin.
b. pyridoxal phosphate.
The carbon skeleton used to make serine is:
a. 3-phosphoglycerate
b. glutamate
c. á-ketoglutarate
d. oxaloacetate
e. pyruvate
a. 3-phosphoglycerate
Which of the following amino acids does not use glutamic acid as a precursor?
a. arginine
b. glutamine
c. lysine
d. proline
c. lysine
Which of the following is not a characteristic of pyridoxal in its active form?
a. It is covalently bonded to its enzyme.
b. It requires being attached to a phosphate group.
c. It bonds to an amine group through by means of the phosphate
group.
d. It has a particularly reactive carbonyl group.
c. It bonds to an amine group through by means of the phosphate group.
Pyridoxal phosphate is involved in which of the following reactions?
a. transaminations
b. decarboxylations
c. racemizations
d. movement of hydroxymethyl groups
e. all of these
e. all of these
A metabolic intermediate that is not a precursor for an amino acid family is
a. α-ketoglutarate
b. pyruvate
c. glyceraldehyde-3-phosphate
d. oxaloacetate
c. glyceraldehyde-3-phosphate
The sulfur group in cysteine arises from the same source in plants, animals and bacteria.
a. True
b. False
b. False
The serine family of amino acids includes synthesis of all the following amino acids, except:
a. Serine.
b. Glycine.
c. Cysteine.
d. Methionine.
e. The serine family includes synthesis of all four of these amino acids.
d. Methionine.
In animals, the synthesis of cysteine involves all of the following, except:
a. Addition of a carbon group to glycine.
b. Transfer of the sulfur group from methionine.
c. An intermediate of homocysteine.
d. Participation of ATP.
e. All of these reactions are involved in synthesizing cysteine in
animals.
a. Addition of a carbon group to glycine.
Isoleucine, leucine and valine are all formed from the same amino acid root, aspartic acid.
a. True
b. False
b. False
There is a curious diversity of nature for the two sulfur containing amino acids. Methionine is made from cysteine in bacteria, but cysteine is made from methionine in mammals.
a. True
b. False
a. True
By a simple transamination reaction, intermediates in glycolysis or the Kreb’s Cycle can be
converted in one step to all of these amino acids, except:
a. Alanine.
b. Aspartic Acid
c. Glutamic Acid.
d. Serine.
e. All of these amino acids are only one step away from the major metabolic
pathways.
d. Serine.
Which of the following are all essential amino acids in humans?
a. leucine, lysine, valine
b. methionine, threonine, serine
c. arginine, histidine, cysteine
d. glutamate, glutamine, arginine
e. valine, isoleucine, glycine
a. leucine, lysine, valine
Essential amino acids cannot be synthesized in sufficient quantities within the human body.
a. True
b. False
a. True
Some amino acids can only be made in small quantities in humans and must be supplemented in the diet in children or during repair of injured tissue.
a. True
b. False
a. True
Kwashiorkor is a malnutrition disease in which high quality proteins are lacking, even if enough calories are available for survival.
a. True
b. False
a. True
In the urea cycle, the molecule that is synthesized in the cytosol and transported to the mitochondrial matrix for subsequent reaction is
a. citrulline
b. ornithine
c. argininosuccinate
d. aspartate
e. fumarate
b. ornithine
Which of the following statements concerning arginine is true?
a. Arginine is only marginally an essential amino acid, since it is made in the urea cycle.
b. Aspartic acid is the main amino acid precursor for the carbon chain in arginine.
c. Lysine could substitute for arginine as a dietary source for arginine.
d. Arginine is only essential in adults.
a. Arginine is only marginally an essential amino acid, since it is made in the urea cycle.
The urea cycle is linked to the citric acid cycle by
a. arginine
b. citrulline
c. fumarate
d. ornithine
c. fumarate
Which of the following is not an intermediate in the urea cycle?
a. arginine
b. citrulline
c. ornithine
d. lysine
d. lysine
The carbon skeletons of many amino acids can be used to replenish the intermediates of the citric acid cycle.
a. True
b. False
a. True
The following two amino acids are key to the transfers of amino groups during breakdown
and synthesis of amino acids.
a. GLU and ASP
b. GLU and ARG
c. GLU and GLN
d. ALA and GLN
e. ASP and GLN
c. GLU and GLN
High protein diets for humans result in the following.
a. Increased nitrogen metabolism.
b. A negative nitrogen balance for the body.
c. Increased demand for water in the diet.
d. Both increased nitrogen metabolism and need for water.
e. All of these are consequences of high protein diets.
d. Both increased nitrogen metabolism and need for water.
Which of the following compounds does not serve as an intermediate for the entry of amino acid carbon chains into the major metabolic pathways?
a. Alpha-ketoglutarate.
b. Pyruvate.
c. Glyceraldehyde.
d. Acetyl CoA.
e. All of these are entry points for amino acid
catabolism.
c. Glyceraldehyde.
Which of the following amino acids is not glucogenic?
a. Glycine.
b. Alanine.
c. Aspartic Acid.
d. Leucine.
e. All of these amino acids are glucogenic.
d. Leucine.
Humans produce these as the major nitrogen waste products.
a. Ammonia.
b. Urea.
c. Uric Acid.
d. Both Urea and Uric Acid.
e. All three of these are used to dispose of nitrogen wastes by
humans.
d. Both Urea and Uric Acid.
If an amino acid is ketogenic, then it:
a. has a catabolic pathway that leads to acetyl-CoA or acetoacetyl-CoA
b. has a one step pathway to a fatty acid
c. enters the citric acid cycle as pyruvate
d. enters the citric acid cycle as fumarate
e. none of these
a. has a catabolic pathway that leads to acetyl-CoA or acetoacetyl-CoA
The form in which nitrogen waste is removed from the body is dependent mostly on the
organism’s availability of water.
a. True
b. False
a. True
A molecule synthesized in the mitochondrial matrix and transported to the cytosol for
subsequent reaction is
a. arginine
b. argininosuccinate
c. citrulline
d. ornithine
c. citrulline
If an amino acid’s degradation pathway leads to α-ketoglutarate, is it glucogenic?
a. Yes.
b. No.
c. Only if the organism has a glyoxylate pathway.
d. Only if the organism does not have a glyoxylate pathway.
a. Yes.
High protein foods are not advisable for the long distance runner during a race because they increase the need for water and for urination.
a. True
b. False
a. True
How many ATP equivalents are required to produce one molecule of urea from ammonia and aspartate?
a. 1
b. 2
c. 3
d. 4
e. 6
d. 4
The two nitrogens in urea arise directly from:
a. Ammonia and aspartic acid.
b. Carbamoyl phosphate and aspartic acid.
c. Carbamoyl phosphate and glutamic acid.
d. Ammonia and glutamic acid.
e. Carbamoyl phosphate and glutamine.
b. Carbamoyl phosphate and aspartic acid.
Which of the following is not associated with purine synthesis?
a. Synthesis of the base while ribose is attached.
b. Stimulation of ATP synthesis by GTP and of GTP synthesis by ATP
c. An Inosine intermediate.
d. Inhibition by pyrimidines.
e. All of these are features of purine synthesis.
d. Inhibition by pyrimidines.
How is cancer chemotherapy related to purine biosyntheis?
a. rapidly dividing cells require more purine biosynthesis and some chemotherapy drugs
inhibit a key enzyme in purine biosynthesis
b. aminopterin is a good chemotherapy drug because it inhibits aspartate
transcarbamoylase
c. cancer cells lack folic acid, and chemotherapy drugs like sulfanamide act by overproducing folic acid, which is then poisonous to the cancer cells
d.none of these
a.rapidly dividing cells require more purine biosynthesis and some chemotherapy drugs
inhibit a key enzyme in purine biosynthesis
In the synthesis of purine nucleotides,
a. the ring system is bonded to ribose phosphate only after the complete purine ring is assembled
b.the six-membered ring of the purine is assembled first, then the five-membered ring
c. there is no requirement for ATP
d.the ring system is synthesized onto the ribose phosphate moiety
d.the ring system is synthesized onto the ribose phosphate moiety
Which best describes the synthesis of purine nucleotides?
a.The basic ring structure, inosine, is synthesized first and then linked to ribose. This is then modified to produce either GMP or AMP.
b.The basic ring structure, orotate, is synthesized stepwise on ribose. This is then
modified to produce either GMP or AMP.
c.The basic ring structure, inosine, is synthesized stepwise on ribose. This is then
modified to produce either GMP or AMP.
d.The basic ring structure, orotate, is synthesized first and then linked to ribose. This is then modified to produce either UMP or CMP.
c.The basic ring structure, inosine, is synthesized stepwise on ribose. This is then
modified to produce either GMP or AMP.
What intermediate of the TCA cycle is produced from aspartic acid during the urea cycle, synthesis of IMP, and conversion from IMP to adenosine?
a. fumarate
b. malate
c. α-ketoglutarate
d. succinate
a. fumarate
The ultimate end products of xanthine catabolsim are:
a. two pyrimidines
b. urea and glyoxylate
c. uric acid
d. allantoin
b. urea and glyoxylate
Purine salvage reactions
a. use bases as the substrate
b. use nucleosides as the substrate
c. produce nucleosides as
products
d. require the hydrolysis of ATP
e. none of these
a. use bases as the substrate
The initial, common intermediate in purine catabolism for both AMP and GMP is
a. xanthine
b. hypoxanthine
c. inosine
d. uric acid
a. xanthine
The energy costs for synthesizing the bases for RNA and DNA is so high that salvage
pathways have been developed to recycle existing bases and nucleotides.
a. True
b. False
a. True
Lesch-Nyhan syndrome involves a genetic error in the pyrimidine salvage pathways.
a. True
b. False
b. False
One way in which the anabolism of pyrimidine nucleotides differs from that of purine nucleotides is that
a.the pyrimidine ring is assembled before being bonded to the ribose phosphate, whereas the purine ring is bonded to the ribose phosphate as it is formed
b.there is no feedback inhibition in the anabolism of pyrimidine nucleotides, while
feedback inhibition is important in the synthesis of purine nucleotides
c.glycine appears in the pathway for formation of pyrimidine nucleotides but not in that for the formation of purine nucleotides
d.argininosuccinate is a key intermediate in pyrimidine biosynthesis
a.the pyrimidine ring is assembled before being bonded to the ribose phosphate, whereas the purine ring is bonded to the ribose phosphate as it is formed
Which of the following is not associated with pyrimidine synthesis?
a. Synthesis of the base while ribose is attached.
b. Stimulation of synthesis by purines.
c. An orotic acid intermediate.
d. Inhibition by pyrimidines.
e. All of these are features of pyrimidine synthesis.
a. Synthesis of the base while ribose is attached.
Carbamoyl phosphate is made in both the mitochondria and the cytosol, because it is used in the synthesis of several different molecules which are made in either of the compartments.
a. True
b. False
a. True
In the synthesis of pyrimidine nucleotides, the ring system formed just before the attachment
of PRPP is
a. 5-aminoimidazole
b. inosine
c. orotate
d. xanthine
c. orotate
Which reaction converts orotate monophosphate into uracil monophosphate?
a. a transamination
b. a methylation
c. a decarboxylation
d. a carboxylation
c. a decarboxylation
Orotic acid is synthesized from
a. glycine and carbamoyl phosphate.
b. arginine and carbamoyl phosphate.
c. aspartic acid and carbamoyl phosphate.
d. aspartic acid and glutamine.
c. aspartic acid and carbamoyl phosphate.
Ribonucleotide reductase uses which of the following cofactors?
a. biotin
b. thiamine pyrophosphate
c. tetrahydrofolate
d. thioredoxin
d. thioredoxin
Deoxyribonucleotides are formed
a. by a pathway entirely different from that of ribonucleotides
b. exclusively by hydrolysis of the DNA of the organism
c. as monophosphates by reduction of ribonucleoside monophosphates
d. as diphosphates by reduction of ribonucleoside disphosphates
d. as diphosphates by reduction of ribonucleoside disphosphates
Many antibiotics, especially for viruses and cancer therapy involve inhibition of folic acid
reactions, especially because folic acid is essential for this reaction:
a. Synthesis of many amino acids.
b.Conversion of uracil to thymine for DNA synthesis.
c. Synthesis of deoxyribose for DNA synthesis.
d.None of these reactions explains the reason why inhibitors of folic acid act as
antibiotics.
e. All of these reactions are reasons why inhibitors of folic acid act as antibiotics.
b.Conversion of uracil to thymine for DNA synthesis.
Folic acid is an important factor necessary for the production of three of the four
deoxyribonucleotides needed for DNA synthesis. For which dNTP is this factor not necessary?
a. dATP
b. dCTP
c. dGTP
d. dTTP
b. dCTP
Cancer treatments which disrupt the function of folic acid have significant side effects, since
this therapy also affects the growth of such rapidly dividing tissues as all of the following, except:
a. Skin cells.
b. Red and white blood cells.
c. Nerve tissue.
d. Sperm.
e. All of these cell types are affected by this therapy.
c. Nerve tissue.
Fluorouracil is an effective inhibitor of
a. ribonucleotide reductase
b. thymidylate synthase
c. xanthine oxidase
d. carbamoyl phosphate
synthetase
b. thymidylate synthase
The conversion of uracil to thymine requires
a. a one-carbon transfer with S-adenosylmethionine as the
donor
b. a one-carbon transfer with tetrahydrofolate as the donor
c. a one-carbon transfer with biotin as the donor
d. a one-carbon transfer with oxaloacetate as the donor
b. a one-carbon transfer with tetrahydrofolate as the donor
Which of the following is not a carrier of one-carbon groups?
a. S-adenosylmethionine
b. biotin
c. tetrahydrofolate
d. thiamine
pyrophosphate
d. thiamine
pyrophosphate
Enzymes which carry out one-carbon transfers can use any of these compounds, except:
a. Biotin
b. Pyridoxal
c. Folic Acid
d. S-adenosylmethionine
e. All of these can carry out one-carbon transfers.
e. All of these can carry out one-carbon transfers.
In the nitrogenase complex, several types of subunits are arranged in _____.
a. octamers
b. hexamers
c. pentamers
d. tetramers
d. tetramers
The amino acids central to the amino acid biosynthesis process are _____.
a. serine and cysteine
b. tyrosine and threonine
c. glutamate and glutamine
d. asparagine and
histamine
c. glutamate and glutamine
Which of the following amino acids is both glucogenic and ketogenic?
a. Phenylalanine
b. Asparagine
c. Methionine
d. Glutamine
a. Phenylalanine
Identify the half reaction of the reduction of molecular nitrogen to an ammonium ion.
a. N2 + 8 e- + 14 ATP + 10 H+ –> 2NH4+ + 14 ADP + 16 Pi + H2
b. N2 + 8 e- + 16 ATP + 10 H+ –> 2NH4+ + 16 ADP + 16 Pi + H2
c. N2 + 8 e- + 12 ATP + 10 H+ –> 2NH4+ + 12 ADP + 16 Pi + H2
d. N2 + 8 e- + 10 ATP + 10 H+ –> 2NH4+ + 10 ADP + 16 Pi + H2
b. N2 + 8 e- + 16 ATP + 10 H+ –> 2NH4+ + 16 ADP + 16 Pi + H2
