Protein Structure, Protein Metabolism and Nucleic Acid Metabolism

Question 1

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

Answer 1

primary structure

Question 2

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

Answer 2

secondary structure

Question 3

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

Answer 3

tertiary structure

Question 4

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

Answer 4

C. tertiary structure

Question 5

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

Answer 5

C. supersecondary structure

Question 6

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

Answer 6

D. quaternary structure

Question 7

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

Answer 7

C. tertiary structure

Question 8

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

Answer 8

covalent bonds

Question 9

A single amino substitution can give rise to a malfunctioning
protein.
A. True
B. False

Answer 9

B. False

Question 10

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.

Answer 10

C. cysteine.

Question 11

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.

Answer 11

A. Its secondary structure is disrupted but its primary structure
remains intact.

Question 12

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.

Answer 12

a supersecondary region, often shared by proteins, that has a
specific function

Question 13

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

Answer 13

C. proline

Question 14

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.

Answer 14

C. a-helices only use intrachain hydrogen bonds and b-sheets can
use either intrachain or interchain hydrogen bonds.

Question 15

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

Answer 15

both of these

Question 16

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.

Answer 16

its a triple helix

Question 17

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

Answer 17

all of these

Question 18

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

Answer 18

reverse turn

Question 19

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

Answer 19

a repetitive supersecondary structure

Question 20

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

Answer 20

all of these

Question 21

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.

Answer 21

B. structural roles.

Question 22

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

Answer 22

D. there are hydrogen bonds parallel to the helix axis

Question 23

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

Answer 23

A. the pyrrole ring

Question 24

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

Answer 24

B. Globular proteins tend to be water soluble

Question 25

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.

Answer 25

tends to increase

Question 26

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.

Answer 26

it is used to hydroxylate prolines in the primary structure of colla gen

Question 27

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.

Answer 27

hydroxyproline requires vitamin C for its synthesis and it holds the collagen helix together

Question 28

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.

Answer 28

C. can be composed of either helical or b-sheet structures.

Question 29

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

Answer 29

contains a heme group

Question 30

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.

Answer 30

globular

Question 31

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

Answer 31

independently folded regions of proteins

Question 32

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

Answer 32

C. glycine and proline

Question 33

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

Answer 33

C. leucine

Question 34

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

Answer 34

C. cysteine

Question 35

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

Answer 35

C. the positions of all atoms can be found by this method

Question 36

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.

Answer 36

A. almost entirely of a-helices.

Question 37

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

Answer 37

D. all of these

Question 38

Heme would best be described as a A. motif. B. domain. C. prosthetic group. D. helix.

Answer 38

prosthetic group

Question 39

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.

Answer 39

C. This lessens the difference in myoglobin's affinity for CO versus O2.

Question 40

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.

Answer 40

C. 2+, Fe(II)

Question 41

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

Answer 41

D. Myoglobin and hemoglobin differ only in one amino acid

Question 42

Which of the following can result in protein denaturation? A. heat B. extremes of pH C. detergents D. all of the above

Answer 42

D. all of the above

Question 43

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

Answer 43

E. All of these are important in tertiary structure

Question 44

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

Answer 44

D. the relative orientation of one polypeptide to another polypeptide in a multisubunit protein

Question 45

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

Answer 45

D. All of these

Question 46

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.

Answer 46

D. Both hydrogen bonds and hydrophobic attraction.

Question 47

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.

Answer 47

B. Fetal Hb binds oxygen more tightly than adult Hb.

Question 48

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.

Answer 48

C. Mb displays simple kinetics of binding while Hb displays cooperativity.

Question 49

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.

Answer 49

C. It is an allosteric enzyme.

Question 50

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.

Answer 50

C. as the pH goes down, Hb binds oxygen less tightly.

Question 51

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.

Answer 51

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

Question 52

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.

Answer 52

B. it is a tetramer, whereas myoglobin is a single polypeptide chain.

Question 53

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.

Answer 53

C. Binding of BPG causes oxygen to dissociate from Hb.

Question 54

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.

Answer 54

A. oxygen binding to hemoglobin is cooperative.

Question 55

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

Answer 55

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

Question 56

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

Answer 56

C. is lower than that of maternal hemoglobin

Question 57

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

Answer 57

all of these

Question 58

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

Answer 58

D. groups of hemoglobin molecules aggregate with each other

Question 59

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

Answer 59

D. collagen

Question 60

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.

Answer 60

E. Increased entropy of solvent water molecules.

Question 61

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

Answer 61

phenylalanine and tryptophan

Question 62

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

Answer 62

B. primary structure

Question 63

Incorrect protein folding resulting in exposure of hydrophobic regions can result in A. aggregation. B. homology. C. liposomes. D. the Bohr effect.

Answer 63

A. aggregation.

Question 64

Proteins that aid in the correct and timely folding of other proteins are called A. motifs. B. chaperones. C. liposomes. D. cooperative.

Answer 64

B. chaperones.

Question 65

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

Answer 65

B. hemoglobin that lacks BPG

Question 66

The following amino acid causes a kink or bend in the a-helix. A. Ala B. Glu C. Lys D. Pro E. Trp

Answer 66

D. Pro

Question 67

Cys-Ala-Gly-Arg-Gln-Met The amino terminal amino acid is ___

Answer 67

Cys

Question 68

Cys-Ala-Gly-Arg-Gln-Met The carboxyl terminal end is ___

Answer 68

Met

Question 69

Cys-Ala-Gly-Arg-Gln-Met The overall, net ionic charge on this peptide at pH=7 would be

Answer 69

+1

Question 70

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

Answer 70

c. N2 to NH4+ or NH3

Question 71

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.

Answer 71

c. nitrate to ammonia.

Question 72

Denitrification is carried out by a. animals. b. green plants. c. soil bacteria. d. all of the above. e. none of these

Answer 72

c. soil bacteria.

Question 73

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.

Answer 73

e. All of these are common bioconversions in the nitrogen cycle.

Question 74

The nitrogen-fixing enzyme system, nitrogenase, is found exclusively in a. plants b. bacteria c. some viruses d. eukaryotic organisms e. mammals

Answer 74

b. bacteria

Question 75

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.

Answer 75

d. 16ATP.

Question 76

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

Answer 76

d. pyridoxal phosphate

Question 77

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

Answer 77

d. 8 electrons.

Question 78

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

Answer 78

b. Many fertilizers are made from ammonia synthesized by the Haber process

Question 79

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

Answer 79

b. False

Question 80

Nitrogenase uses which of the following cofactors? a. molybdenum-iron-sulfur complex b. biotin c. pyridoxal phosphate d. thiamine pyrophosphate e. none of these

Answer 80

a. molybdenum-iron-sulfur complex

Question 81

Nitrogen fixation in legumes may use as much as half of the ATP made in the plant. a. True b. False

Answer 81

a. True

Question 82

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

Answer 82

a. They are all inhibitors of glutamine synthase

Question 83

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

Answer 83

d. All of these

Question 84

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

Answer 84

d. it commonly appears in biosynthesis of amino acids

Question 85

The conversion of α-ketoglutarate to glutamate is a. a transamination. b. a reductive amination. c. an amidation. d. an oxidation. e. an isomerization

Answer 85

b. a reductive amination.

Question 86

The conversion of glutamate to glutamine is catalyzed by glutamine synthetase and requires ATP. a. True b. False

Answer 86

a. True

Question 87

The synthesis of amino acids occurs in about 5 or 6 related families of amino acids. a. True b. False

Answer 87

a. True

Question 88

Pyridoxal phosphate forms a Schiff base with amino groups in transaminase reactions. a. True b. False

Answer 88

a. True

Question 89

A coenzyme frequently encountered in transamination reactions is a. tetrahydrofolate. b. pyridoxal phosphate. c. thiamine pyrophosphate. d. biotin.

Answer 89

b. pyridoxal phosphate.

Question 90

The carbon skeleton used to make serine is: a. 3-phosphoglycerate b. glutamate c. á-ketoglutarate d. oxaloacetate e. pyruvate

Answer 90

a. 3-phosphoglycerate

Question 91

Which of the following amino acids does not use glutamic acid as a precursor? a. arginine b. glutamine c. lysine d. proline

Answer 91

c. lysine

Question 92

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.

Answer 92

c. It bonds to an amine group through by means of the phosphate group.

Question 93

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

Answer 93

e. all of these

Question 94

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

Answer 94

c. glyceraldehyde-3-phosphate

Question 95

The sulfur group in cysteine arises from the same source in plants, animals and bacteria. a. True b. False

Answer 95

b. False

Question 96

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.

Answer 96

d. Methionine.

Question 97

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.

Answer 97

a. Addition of a carbon group to glycine.

Question 98

Isoleucine, leucine and valine are all formed from the same amino acid root, aspartic acid. a. True b. False

Answer 98

b. False

Question 99

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

Answer 99

a. True

Question 100

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.

Answer 100

d. Serine.

Question 101

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

Answer 101

a. leucine, lysine, valine

Question 102

Essential amino acids cannot be synthesized in sufficient quantities within the human body. a. True b. False

Answer 102

a. True

Question 103

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

Answer 103

a. True

Question 104

Kwashiorkor is a malnutrition disease in which high quality proteins are lacking, even if enough calories are available for survival. a. True b. False

Answer 104

a. True

Question 105

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

Answer 105

b. ornithine

Question 106

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.

Answer 106

a. Arginine is only marginally an essential amino acid, since it is made in the urea cycle.

Question 107

The urea cycle is linked to the citric acid cycle by a. arginine b. citrulline c. fumarate d. ornithine

Answer 107

c. fumarate

Question 108

Which of the following is not an intermediate in the urea cycle? a. arginine b. citrulline c. ornithine d. lysine

Answer 108

d. lysine

Question 109

The carbon skeletons of many amino acids can be used to replenish the intermediates of the citric acid cycle. a. True b. False

Answer 109

a. True

Question 110

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

Answer 110

c. GLU and GLN

Question 111

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.

Answer 111

d. Both increased nitrogen metabolism and need for water.

Question 112

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.

Answer 112

c. Glyceraldehyde.

Question 113

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.

Answer 113

d. Leucine.

Question 114

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.

Answer 114

d. Both Urea and Uric Acid.

Question 115

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

Answer 115

a. has a catabolic pathway that leads to acetyl-CoA or acetoacetyl-CoA

Question 116

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

Answer 116

a. True

Question 117

A molecule synthesized in the mitochondrial matrix and transported to the cytosol for subsequent reaction is a. arginine b. argininosuccinate c. citrulline d. ornithine

Answer 117

c. citrulline

Question 118

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.

Answer 118

a. Yes.

Question 119

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

Answer 119

a. True

Question 120

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

Answer 120

d. 4

Question 121

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.

Answer 121

b. Carbamoyl phosphate and aspartic acid.

Question 122

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.

Answer 122

d. Inhibition by pyrimidines.

Question 123

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

Answer 123

a.rapidly dividing cells require more purine biosynthesis and some chemotherapy drugs inhibit a key enzyme in purine biosynthesis

Question 124

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

Answer 124

d.the ring system is synthesized onto the ribose phosphate moiety

Question 125

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.

Answer 125

c.The basic ring structure, inosine, is synthesized stepwise on ribose. This is then modified to produce either GMP or AMP.

Question 126

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

Answer 126

a. fumarate

Question 127

The ultimate end products of xanthine catabolsim are: a. two pyrimidines b. urea and glyoxylate c. uric acid d. allantoin

Answer 127

b. urea and glyoxylate

Question 128

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

Answer 128

a. use bases as the substrate

Question 129

The initial, common intermediate in purine catabolism for both AMP and GMP is a. xanthine b. hypoxanthine c. inosine d. uric acid

Answer 129

a. xanthine

Question 130

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

Answer 130

a. True

Question 131

Lesch-Nyhan syndrome involves a genetic error in the pyrimidine salvage pathways. a. True b. False

Answer 131

b. False

Question 132

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

Answer 132

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

Question 133

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.

Answer 133

a. Synthesis of the base while ribose is attached.

Question 134

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

Answer 134

a. True

Question 135

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

Answer 135

c. orotate

Question 136

Which reaction converts orotate monophosphate into uracil monophosphate? a. a transamination b. a methylation c. a decarboxylation d. a carboxylation

Answer 136

c. a decarboxylation

Question 137

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.

Answer 137

c. aspartic acid and carbamoyl phosphate.

Question 138

Ribonucleotide reductase uses which of the following cofactors? a. biotin b. thiamine pyrophosphate c. tetrahydrofolate d. thioredoxin

Answer 138

d. thioredoxin

Question 139

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

Answer 139

d. as diphosphates by reduction of ribonucleoside disphosphates

Question 140

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.

Answer 140

b.Conversion of uracil to thymine for DNA synthesis.

Question 141

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

Answer 141

b. dCTP

Question 142

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.

Answer 142

c. Nerve tissue.

Question 143

Fluorouracil is an effective inhibitor of a. ribonucleotide reductase b. thymidylate synthase c. xanthine oxidase d. carbamoyl phosphate synthetase

Answer 143

b. thymidylate synthase

Question 144

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

Answer 144

b. a one-carbon transfer with tetrahydrofolate as the donor

Question 145

Which of the following is not a carrier of one-carbon groups? a. S-adenosylmethionine b. biotin c. tetrahydrofolate d. thiamine pyrophosphate

Answer 145

d. thiamine pyrophosphate

Question 146

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.

Answer 146

e. All of these can carry out one-carbon transfers.

Question 147

In the nitrogenase complex, several types of subunits are arranged in _____. a. octamers b. hexamers c. pentamers d. tetramers

Answer 147

d. tetramers

Question 148

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

Answer 148

c. glutamate and glutamine

Question 149

Which of the following amino acids is both glucogenic and ketogenic? a. Phenylalanine b. Asparagine c. Methionine d. Glutamine

Answer 149

a. Phenylalanine

Question 150

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

Answer 150

b. N2 + 8 e- + 16 ATP + 10 H+ --> 2NH4+ + 16 ADP + 16 Pi + H2