Deck 21: Amino Acid Metabolism

Question 1

Which of the following glycolytic intermediates is the common precursor to serine,cysteine,and glycine?

A)fructose-6-phosphate
B)glyceraldehyde-3-phosphate
C)dihydroxyacetone phosphate
D)3-phosphoglycerate
E)pyruvate

Answer 1

3-phosphoglycerate

Question 2

The lifetime of a protein in cells actively involved in metabolism

A)is longer in eukaryotes than in prokaryotes.
B)ranges from months to years.
C)is independent of the function and activity of the protein.
D)can change in response to changes in metabolic hormone levels.
E)none of the above

Answer 2

can change in response to changes in metabolic hormone levels.

Question 3

The neurotransmitters,dopamine,epinephrine,and norepinephrine are synthesized from the amino acid

A)tryptophan
B)tyrosine
C)glutamate
D)aspartate
E)lysine

Answer 3

tyrosine

Question 4

The aminotransferase reaction,in which an enzyme-PLP Schiff base forms,
(I)is ATP dependent.
(II)results in formation of a hydroxylaldehyde.
(III)results in formation of an $\alpha$ -ketoacid.
(IV)requires an active site lysine.

A)I,III,IV
B)I,IV
C)II,III
D)I,II,III
E)II,III,IV

Question 5

Matching
Choose the correct answer from the list.Not all the answers will be used.

A phenomenon in which intermediates are directly transferred from one active site to another is ______.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 6

The majority of amino acids are deaminated by a ______ reaction.

A)transaminmation
B)reduction
C)condensation
D)transacetylation
E)oxidation

Question 7

Which of the following describes the steps required prior to ATP-dependent degradation of proteins?
(I)Ubiquitin is transferred to cysteine on a ubiquitin-conjugating enzyme.
(II)The protein is linked to at least four tandemly linked ubiquitin units.
(III)Activated ubiquitin is transferred to a lysine of the previously bound protein.
(IV)Ubiquitin is attached via a thioester to a unbiquitin-activiating enzyme.

A)I,II,III,IV
B)IV,I,III,II
C)II,I,III,IV
D)IV,II,I,III
E)IV,II,III,I

Question 8

Nitrogenase
(I)can be found in most bacteria and a few invertebrate animals.
(II)contains unique redox centers that contain both Fe and Mo.
(III)changes in conformation as a result of ATP hydrolysis.
(IV)carries out a reaction that reduces nitrogen to NO.

A)I,II,III,IV
B)II,III,IV
C)II,III
D)III,IV
E)IV only

Question 9

Matching
Choose the correct answer from the list.Not all the answers will be used.

Infants who cannot properly degrade bilirubin develop ______.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 10

Matching
Choose the correct answer from the list.Not all the answers will be used.

The cofactor ______ is used to transfer C₁ units such as methyl,formyl,and methenyl groups.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 11

The total cost of nitrogen reduction is ____ and ___ transferred electrons.

A)8 ATP;4
B)12 ATP;8
C)12 ATP;6
D)16 ATP;8
E)16 ATP;6

Question 12

Matching
Choose the correct answer from the list.Not all the answers will be used.

Aminotransferases utilize a coenzyme synthesized from ______.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 13

Which of the following reaction sequences could result in glucose synthesis?

A)fumarate $\to$ arginine $\to$ urea
B)fumarate $\to$ malate $\to$ oxaloacetate
C)citrulline $\to$ urea $\to$ aspartate
D)urea $\to$ arginine $\to$ ornithine
E)none of the above

Question 14

Matching
Choose the correct answer from the list.Not all the answers will be used.

ATP-dependent degradation of ubiquitinated proteins is mediated by ______.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 15

Matching
Choose the correct answer from the list.Not all the answers will be used.

_____ are involved in the nonselective degradation of proteins in well nourished cells.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 16

Ketogenic amino acids can be converted to
(I)glucose
(II)fatty acids
(III)ketone bodies
(IV)pyruvate

A)I,III
B)II,IV
C)I,II
D)I,II,III
E)I,IV

Question 17

The amino acids Ala,Cys,Gly,Ser,and Thr are all degraded to the metabolic intermediate ___ and are considered ____.

A)acetyl-CoA;glucogenic
B)acetyl-CoA;ketogenic
C)pyruvate;glucogenic
D)pyruvate;ketogenic
E)acetoacetate;ketogenic

Question 18

Matching
Choose the correct answer from the list.Not all the answers will be used.

The enzyme ______ is critical to regulating nitrogen metabolism.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 19

Matching
Choose the correct answer from the list.Not all the answers will be used.

Organisms known as _____ can fix nitrogen into metabolically useful molecules.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 20

Matching
Choose the correct answer from the list.Not all the answers will be used.

The amino acid ______ has been thought to act as a transfer system for NH₃,safely allowing the toxic molecule to be transported from the liver to the kidneys.

A) ribosomes
B) jaundice
C) channeling
D) 26S proteasome
E) glutamine synthetase
F) alanine
G) glutamate
H) vitamin B₆
I) anammox
J) glutamine transferase
K) THF
L) autotroph
M) vitamin D
N) lysosomes
O) diazotrophs

Question 21

Which of the following amino acids is NOT synthesized from aspartate?

A)threonine
B)methionine
C)lysine
D)cysteine
E)All of the above are synthesized from aspartic acid.

Question 22

In which cellular location listed below does the following reaction take place?
Ornithine + carbamoyl-phosphate → citrulline

A)cytosol
B)mitochondrial matrix
C)lysosome
D)A or B
E)none of the above

Question 23

What species are combined to produce carbamoyl phosphate?

A)NH₃ ,PO₄³⁻,HCO₃⁻
B)NH₄⁺,PO₄³⁻,Ac-CoA,releasing CoA-SH
C)glycine & inorganic phosphate,releasing CO₂
D)acetate & NH₄⁺,releasing CO₂
E)alanine & inorganic phosphate,releasing acetate

Question 24

Which of the following statements about phenylalanine is(are)TRUE?

A)The enzymatic degradation of phenylalanine requires the biopterin cofactor.
B)Individuals with defects in phenylalanine catabolism require tyrosine in their diet.
C)An inability to hydroxylate phenylalanine results in increased blood levels of phenylalanine,causing mental retardation.
D)A and C
E)A,B,and C

Question 25

The pictured compound,glutamate-5-semialdehyde,is an intermediate in the biosynthesis of which of the following amino acids?

A)histidine
B)arginine
C)methionine
D)threonine
E)More than one of the above is made from this intermediate.

Question 26

In which cellular location listed below does the following reaction take place?
Arginine → urea + ornithine

A)cytosol
B)mitochondrial matrix
C)lysosome
D)A or B
E)none of the above

Question 27

Proteins targeted for destruction via the ubiquitin pathway include
(I)proteins with a destabilizing N-end rule component.
(II)proteins with a PEST sequence.
(III)proteins that contain the RING finger E3 component named E3a.
(IV)protein with polyubiquitin proteins.

A)I only
B)II only
C)I,II,III
D)I,II,IV
E)II,IV

Question 28

Which of the following is(are)advantages to the constant degradation and reformation of proteins?

A)Nutrients can be stored as proteins,which can be used during periods of metabolic need.
B)Damaged proteins are eliminated so they do not accumulate.
C)Metabolism can be efficiently regulated by the synthesis and degradation of enzymes.
D)All of the above are advantages.
E)None of the above is an advantage.

Question 29

_____ catalyzes the synthesis of ____,a molecule that signals vasodilation,from the precursor _____

A)NOS;nitric oxide (NO);arginine
B)Nitrous oxidase;nitrous oxide;arginine
C)Arginate;nitric oxide (NO);citrulline
D)Citrulline dehydrogenase;nitrous oxide;citrulline
E)none of the above

Question 30

The metabolite chorismate

A)allosterically enhances production of aromatic amino acids.
B)is an important intermediate in the production of Trp,Tyr,and Phe.
C)is a derivative of glucose.
D)A and B
E)B and C

Question 31

Oxidative deamination of glutamate
(I)generates NAD(P)H and $\alpha$ -ketoglutarate.
(II)is inhibited by glutamate.
(III)is activated by GTP.
(IV)eliminates the keto group from $\alpha$ -ketoacids.

A)I only
B)I,II
C)I,III
D)II,IV
E)III,IV

Question 32

What are KFERQ proteins?
(I)Proteins that contain the KFERQ pentapeptide sequence (or a similar sequence).
(II)Proteins that are selectively degraded in tissues that atrophy after a prolonged fast (starvation).
(III)A special set of enzymes that are activated in response to starvation.

A)I,II
B)I,II,III
C)II,III
D)I,III
E)I only

Question 33

Which of the following statements about maple syrup urine disease is FALSE?
(I)It is caused by a genetic deficiency in the enzyme BCKDH.
(II)The disease is fatal unless promptly treated.
(III)There is a buildup of the branched-chain $\alpha$ -keto acids.
(IV)Patients with the disease excrete urine that smells like maple syrup.

A)I only
B)II only
C)I,III
D)III,IV
E)All of the statements are true.

Question 34

Which enzyme catalyses a reaction via an enzyme-bound adenylated intermediate?

A)glutamine synthetase
B)argininosuccinate synthetase
C)carbamoyl phosphate synthetase I
D)Ac-CoA decarboxylase
E)arginase

Question 35

Which of the following statements about tryptophan synthase is FALSE?

A)Indole can pass between active sites via a channel in the enzyme.
B)Tryptophan synthase catalyzes two distinct reaction steps to form tryptophan.
C)The enzyme is a tetramer of four identical subunits.
D)The enzyme has two states,an "open" and "closed",to ensure that bound indole is not lost to solvent.
E)The indole group is produced following release of glyceraldehyde-3-phosphate from the indole-glycerol-3-phosphate.

Question 36

A number of compounds,including neurotransmitters,are synthesized from amino acids via decarboxylations.The enzymes catalyzing these steps usually use _______ as a cofactor.

A)pyridoxal-5ꞌ-phosphate
B)thiamine pyrophosphate
C)biotin
D)cobalt containing compounds [vitamin B₁₂]
E)tetrahydrofolate

Question 37

The activity of bacterial glutamine synthetase is
(I)inhibited allosterically by tryptophan.
(II)inhibited allosterically by glucosamine-6-phosphate.
(III)activated by nine allosteric feedback inhibitors.
(IV)altered by covalent modification.

A)I,III
B)III,IV
C)I,II
D)I,IV
E)I,II,III,IV

Question 38

Heme biosynthesis

A)requires that synthesis of the protoporphryin ring occur in the mitochondria due to difficulties in transporting large molecule.
B)is inhibited in lead poisoning.
C)can be completed using enzymes from the cytosol.
D)A and B
E)A,B,and C

Question 39

The presence of SGOT and SGPT in the serum indicate potential

A)starvation and brain tissue damage.
B)inflammation.
C)heart attack or liver damage.
D)lung or breast cancer.
E)none of the above

Question 40

Which of the following is TRUE regarding catabolism of leucine?

A)The pathway begins with aspartate.
B)The pathway requires $\alpha$ -ketoglutarate.
C)The pathway requires TPP.
D)The pathway generates HMG-CoA.
E)none of the above

Question 41

Which of the following require a cyclic carbohydrate precursor for synthesis?
(I)histidine
(II)alanine
(III)arginine
(IV)tyrosine

A)I,II
B)II only
C)I,III
D)I ,IV
E)II,IV

Question 42

A mutation in GDH of patients with HI/HA (hypoglycemia/hyperammonemia)results in a decrease in allosteric control of GDH via GTP.Which of the following will be observed in the patients?

A)an increase in ammonia
B)an increase in glutamate
C)an increase in NADH
D)A and B
E)A and C

Question 43

Which of the following are essential amino acids for adult humans?

A)Arg,His,Gly,Try
B)Met,Lys,His,Val
C)His,Leu,Tyr,Ala
D)Met,Gly,Thr,Ser
E)Ala,Arg,Cys,Ser

Question 44

The synthesis of which of the following uses an aminotransferase in the first step of the synthesis?

A)glutamine
B)proline
C)serine
D)valine
E)all of the above

Question 45

Enzyme A is involved in the metabolism of metabolite C to metabolite D.Enzyme A is part of a linear pathway involving ten enzymes ultimately converting B $\to$ F.High levels of F directly alter the activity of enzyme A and result in control over the overall pathway.Enzyme A

A)likely has high rates of degradation and synthesis.
B)is likely a nonessential enzyme.
C)likely has low rates of degradation and synthesis.
D)is likely involved in a nonessential pathway.
E)none of the above

Question 46

Individuals with an alanine to valine mutation in N⁵,N¹⁰ - methylenetetrahydrofolate reductase (MTHFR)
(I)typically have higher levels of homocysteine.
(II)have increased risk for cardiovascular disease.
(III)typically have increased incidence of oxidative damage to the walls of blood vessels.
(IV)are at increased risk,if female,of giving birth to a child with a neural tube defect.

A)I,II
B)II,III
C)I only
D)IV only
E)I,II,III,IV

Question 47

Which of the following amino acid breakdown reactions would be catalyzed by an aminotransferase?

A)Threonine $\to$ Acetyl CoA
B)Alanine $\to$ Pyruvate
C)Asparagine $\to$ Aspartate
D)Homocysteine $\to$ Methionone
E)HMG-CoA $\to$ Acetoacetate

Question 48

Which of the following control the urea cycle?
(I)substrate concentration of the cycle enzymes
(II)allosteric activation of carbamoyl phosphate synthetase I
(III)concentration of glutamate
(IV)availability of glucose

A)I,III
B)II,III
C)II,IV
D)I,II,III
E)I,IV

Question 49

Which of the following is required for synthesis of tryptophan?

A)serine
B)phosphoenolpyruvate
C)erythrose-4-phosphate
D)all of the above
E)none of the above

Question 50

Which of the following is TRUE about glutamine?
(I)It is formed from $\alpha$ -ketoglutarate.
(II)It donates an amino group to aspartate to form asparagine.
(III)It is directly required for ornithine synthesis.
(IV)It is a precursor to homoserine.

A)I,II
B)I,II,III
C)II,III,IV
D)II,IV
E)I,III