Deck 17: Amino Acid Metabolism

Question 1

Which of the following is an amide-containing amino acid?

A)Alanine.
B)Arginine.
C)Aspartate.
D)Asparagine.

Answer 1

Asparagine.

Question 2

Microorganisms capable of fixing nitrogen into a form usable by animals obtain the energy for this process from ________.

A)lightning
B)oxidation and reduction (respiration)
C)photosynthesis of host plants
D)soil nutrients

Answer 2

photosynthesis of host plants

Question 3

An amino acid formed by transamination of a citric acid cycle intermediate is ________.

A)aspartate
B)cysteine
C)serine
D)alanine

Answer 3

aspartate

Question 4

Which of the following is/are true concerning transanimation reactions?

A)They can convert α-keto acids to α-amino acids.
B)All require the coenzyme pyridoxal phosphate.
C)The catalyzed reactions are near-equilibrium.
D)All of the above.

Question 5

Nitrogenases

A)are protected from oxygen to prevent inactivation.
B)consist of two protein components.
C)contain an electron transport system.
D)A and B only.
E)All of the above.

Question 6

At neutral pH,the main ionic form of ammonia is ________.

A)N₂
B)NH₄+
C)NH₃
D)NH₂-
E)None of the above

Question 7

Nitrogen fixation may occur via all of the following bacteria,except

A)Azotobacter.
B)Klebsiella.
C)cyanobacteria.
D)E.coli.

Question 8

Glutamate dehydrogenase has different roles in different organisms.Which of these listed is mismatched?

A)E.coli (bacterium)- generates NH₄+ + glutamate.
B)N.crassa (fungus)- aminates α-ketoglutarate.
C)Mammals - degradation of amino acids and release of NH₄+.
D)Mammals - formation of glutamate.

Question 9

α-ketoglutarate is a precursor for each of the following,except

A)glutamine.
B)arginine.
C)proline.
D)glycine.

Question 10

Because they lack aspartate kinase and aspartate semialdehyde dehydrogenase,________ cannot synthesize lysine,methionine or threonine.

A)bacteria
B)fungi
C)tobacco plants
D)mammals

Question 11

Transamination reactions require which coenzyme?

A)Pyridoxal phosphate.
B)Thiamine pyrophosphate.
C)Adensosine triphosphate.
D)Flavin mononucleotide.

Question 12

Industrially,nitrogen for use in fertilizers is converted to ammonia by ________.

A)a simple,energy efficient reaction of N₂ with water
B)a cryogenic (very low temperature)process between N₂ and H₂
C)special catalysts which drive the reduction of N₂ by H₂
D)a reaction between nitric acid and hydrogen gas

Question 13

Physiological roles for glutamate dehydrogenase include all of the following,except

A)the generation of glutamate when NH₄+ is present at high concentrations in E.coli.
B)the conversion of glutamate to glutamine in most organisms.
C)the use of an NADPH-dependent enzyme for reductive amination in Neurospora crassa.
D)the degradation of amino acids and generation of NH₄+ in mammals.

Question 14

A key precursor in the synthesis of aromatic amino acids (tryptophan,tyrosine and phenylalanine)is ________.

A)prephenate
B)chorismate
C)4-hydroxyphenylpyruvate
D)indole

Question 15

Which is not part of the synthesis reactions for histidine?

A)Phosphoribosyl pyrophosphate (PRPP).
B)Glutamine.
C)Imidazole glycerol phosphate.
D)Indole glycerol phosphate.
E)None of the above.

Question 16

Which of the following amino acids is/are derived from 3-phosphoglycerate?

A)Serine.
B)Glycine.
C)Cysteine.
D)All of the above.

Question 17

What would be the product of the transamination of the structure shown below? (The unionized forms are shown. )

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

Question 18

Aspartate is the precursor for which of the following amino acids?

A)Lysine.
B)Threonine.
C)Methionine.
D)All of the above.

Question 19

Ammonia is incorporated into amino acids via which of the following?

A)Glutamate.
B)Glutamine.
C)Carbamoyl phosphate.
D)All of the above.

Question 20

Which of the following is/are true statement(s)about glutamine?

A)It is a nitrogen donor in many biosynthetic reactions.
B)It is a nitrogen source for glutamate synthase.
C)It carries nitrogen and carbon between tissues,thus avoiding high toxic levels of NH₄+ in blood.
D)All of the above.

Question 21

What type of reaction is shown below? Amino acid + α-Ketoglutarate⇋ α-Keto acid + Glutamate

A)Reductive amination.
B)Oxidation.
C)Transamination.
D)Hydrolysis.

Question 22

Defects in which of the following may result in elevated levels of phenylalanine?

A)Deficiencies in dihydropteridine reductase.
B)Deficiencies in 4a-carbinolamine dehydratase.
C)Defects in the biosynthesis of tetrahydrobiopterin.
D)All of the above.

Question 23

Glycine is a precursor for all of the following except

A)cytidine.
B)creatine phosphate.
C)porphobilinogen.
D)bile salts.
E)glyoxylate.

Question 24

Nitric oxide is formed from arginine.It is a messenger molecule with several functions that include all below except

A)macrophage activation.
B)reacting with superoxide anions to form more toxic substances.
C)constricting red blood cells.
D)neurotransmitter in the brain.

Question 25

Which is not produced from the degradation of branched-chain amino acids?

A)Succinyl CoA.
B)Acetyl CoA.
C)Malonyl CoA.
D)Propionyl CoA.

Question 26

A Roundup Ready plant is one that has been genetically modified so that an enzyme (EPSP synthase)can no longer bind to the active ingredient (glyphosphate)which is a competitive inhibitor of

A)shikimate (in the aromatic amino acid pathway).
B)tryptophan.
C)lysine.
D)phosphoenolpyruvate (PEP).

Question 27

The degradation of which amino acid requires the coenzyme tetrahydrofolate?

A)Histidine.
B)Leucine.
C)Cysteine.
D)Alanine.

Question 28

Phenylketonuria (PKU)is a disease caused by a defect in ________ formation.

A)phenylalanine
B)α-ketoglutarate
C)tyrosine
D)urea

Question 29

Nitric oxide,which can be produced from arginine,is an example of a(n)________.

A)nitrogen fixation end-product
B)reactive free radical
C)stable gaseous solute in the blood
D)aromatic compound

Question 30

The changes that occur in cells that lead to its death are called ________.

A)cellular necroptosis
B)programmed lysis
C)apoptosis
D)morpholytic degradation

Question 31

Nitric oxide is produced from which reaction?

A)Arginine to citrulline.
B)Glutamate to α-ketoglutarate.
C)Bicarbonate to carbamoyl phosphate.
D)Tryptophan to acetyl CoA.

Question 32

Which of these types of proteins are likely to have short half-life and be specifically targeted for degradation?

A)Hormone protein.
B)Mutated (abnormal protein).
C)Transport protein.
D)Structural protein.

Question 33

The conversion of tetrahydrofolate to methylene tetrahydrofolate is coupled to which amino acid conversion?

A)glycine → alanine
B)glutamate → glutamine
C)serine → threonine
D)serine → glycine

Question 34

In amino acid catabolism the α-amino groups are initially released as ________.

A)nitrous oxide
B)ammonium ion
C)nitrate ion
D)glutamine

Question 35

ATP is required to degrade many proteins because it is required to

A)form the proteosome.
B)attach ubiquitin to the target protein.
C)hydrolyze a ubiquitinated protein.
D)All of the above.

Question 36

If an amino acid is glucogenic,it will not be degraded to ________.

A)pyruvate
B)glutamate
C)fumarate
D)acetoacetate

Question 37

The proteases responsible for cell death are called ________.They cleave on the carboxyl side of ________ residues.

A)caspases;aspartate
B)trypsins;lysine and arginine
C)carnitines;cysteine
D)ureases;uridine

Question 38

Malignant lymphocytes of patients with acute lymphoblastic leukemia can be treated with injections of bacterial asparaginase because

A)the levels of asparagine in malignant cells is too high.
B)this reduces the levels of asparagine in blood plasma and that starves malignant cells.
C)this increases the levels of asparagine in blood plasma and this promotes destruction of malignant cells.
D)the levels of asparagine in malignant cells is too low.

Question 39

Which statement is false about protein turnover?

A)The turnover rate is directly proportional to the stability of the protein's tertiary structure.
B)Rapid turnover ensures that some regulatory proteins are degraded so that the cell can respond to changing conditions.
C)The half-life of a given protein is similar in different organs and species.
D)Turnover rates vary to give half-lives from a few minutes to several weeks.

Question 40

The degradation of arginine,histidine and proline all lead to the product ________.

A)pyruvate
B)acetyl CoA
C)acetoacetate
D)glutamate

Question 41

The structure shown below is ________.

A)urea
B)uridine
C)uric acid
D)carbodiamine

Question 42

A patient is experiencing uncontrolled diabetes mellitus with an overproduction of β-hydroxybutyric acid.Which statement is false?

A)The patient will exhale extra amounts of carbon dioxide.
B)Glutamine will be catabolized to reform lost bicarbonate ion.
C)The basic amino acids,lysine and arginine,neutralize the β-hydroxybutyric acid in the blood.
D)The anion of β-hydroxybutyric acid will be excreted in the urine.

Question 43

At the subcellular level where does the urea cycle occur?

A)Mitochondrial matrix only.
B)Mitochondrial matrix and the mitochondrial inner membrane.
C)Mitochondrial matrix and the cytosol.
D)Cytosol only.

Question 44

In the urea cycle the nitrogen atoms originate from ________.

A)α-ketoglutarate
B)ornithine
C)lysine
D)aspartate

Question 45

Which statement(s)applies(apply)to urea?

A)Highly soluble in water.
B)Produced in the liver.
C)Major solute in urine of mammals.
D)Compound used as a means of removing excess nitrogen.
E)All of the above.

Question 46

Which disease is caused by a defect in ornithine transaminase activity?

A)Alcaptonuria.
B)Gyrate atrophy.
C)Cystinuria.
D)Maple syrup urine disease.
E)Nonketotic hyperglycinemia.

Question 47

Birds and many land reptiles convert surplus ammonia to ________,which is relatively water insoluble.

A)urea
B)citrulline
C)glutamate
D)uric acid

Question 48

In mammals,ureagenesis occurs almost exclusively in the ________.

A)liver
B)kidney
C)pancreas
D)lining of the small intestine

Question 49

The glucose-alanine cycle provides ________.

A)an alternate site for production of urea in the kidney
B)transport of important enzymes for gluconeogenesis
C)an indirect means for muscle to eliminate nitrogen and replenish its energy supply
D)a cycle for the direct synthesis of carbohydrates in muscle

Question 50

The enzyme ________ is one of the most abundant in liver mitochondria and catalyzes the synthesis of the molecule shown below.

A)arginase
B)carbamoyl phosphate synthetase I
C)4-α-carbinolamine dehydratase
D)transaminase

Question 51

Which type of organisms can eliminate excess nitrogen by the direct excretion of ammonia?

A)Mammals.
B)Birds.
C)Fish.
D)Reptiles.

Question 52

________ is hydrolytically cleaved to directly yield urea in the urea cycle.

A)Ornithine
B)Glutamate
C)Arginine
D)Carbamoyl phosphate

Question 53

The carbon in urea originates from ________.

A)aspartate
B)ornithine
C)bicarbonate
D)ATP

Question 54

Phenylalanine hydroxylase requires molecular ________ and tetrahydrobiopterin.

A)hydrogen
B)nitrogen
C)water
D)oxygen

Question 55

The glucose-alanine cycle provides a mechanisms for ________ tissue to eliminate nitrogen and replenish its energy supply.

A)liver
B)kidney
C)muscle
D)lung

Question 56

Which of the following supplies a nitrogen atom to carbamoyl phosphate in the urea cycle?

A)Aspartate.
B)α-ketoglutarate.
C)Lysine.
D)Ornithine.

Question 57

In mammals,most amino acids undergo deamination in the ________.

A)liver
B)kidney
C)pancreas
D)mitochondria of all cell types

Question 58

In the urea cycle which molecule is transported from the mitochondrial matrix to the cytosol as ornithine is transported in the opposite direction?

A)Arginine.
B)Citrulline.
C)Glutamate.
D)Carnitine.

Question 59

Which amino acids are purely ketogenic?

A)Arginine and lysine.
B)Valine and isoleucine.
C)Tryptophan only.
D)Lysine and leucine.
E)All essential amino acids.

Question 60

Mammalian carbamoyl phosphate synthetase I

A)is one of the most abundant enzymes in liver mitochondria.
B)is involved in the urea cycle.
C)catalyzes the synthesis of carbamoyl phosphate from bicarbonate and ammonia.
D)A and B only.
E)All of the above.

Question 61

Oxaloacetate is the amino-group acceptor in the synthesis of aspartate.

Question 62

Tryptophan synthase's a subunit catalyzes the cleavage of indole glycerol phosphate to glyceralde 3-phosphate and indole.

Question 63

Chorismate is a key branch-point intermediate in aromatic amino acid synthesis.

Question 64

Nitric oxide is a very reactive compound.In vivo it reacts with oxygen and water to form nitrates and nitrites within seconds.

Question 65

In animals glutamate synthase is essential for the production of glutamate.

Question 66

A large percentage of nitrogen,undergoing metabolism,comes from nitrogen fixation.

Question 67

During the catabolism of amino acids,the carbon skeleton is first degraded,followed by the removal of the amino group.

Question 68

Virtually all of the nitrogen used in metabolism comes directly from nitrogen fixation.

Question 69

The essential amino acids are those that mammals cannot synthesize,but must obtain from the diet.

Question 70

Most green plants contain both nitrate reductase and nitrite reductase to reduce nitrogen oxides to ammonia.

Question 71

Amino acids that are degraded to pyruvate or citric acid cycle intermediates are called ketogenic.

Question 72

Nitric oxide functions as a neurotransmitter in the brain.

Question 73

Only growing and reproducing cells require a continuous supply of amino acids for the synthesis of new protein molecules.

Question 74

All 20 common amino acids are metabolized through the citric acid cycle by first being converted to either pyruvate or acetyl CoA.

Question 75

Protein turnover of regulatory proteins helps cells to quickly respond to changing conditions.

Question 76

The catabolism of which amino acids can produce sulfuric acid?

A)cysteine and methionine
B)cysteine and serine
C)aspartate and glutamate
D)lysine and arginine

Question 77

Nitrogenase catalyzes the reduction of N₂ to nitrate.

Question 78

Which is an important intermediate in the production of bicarbonate ion from the metabolism of glutamine?

A)Glucose.
B)α-ketoglutarate.
C)Citrulline.
D)Ammonium ion.

Question 79

Acids are often produced in the body as metabolic end products.These acids are neutralized in the blood,which depletes the blood's ________ supply.

A)carbon dioxide
B)acetate ion
C)histidine
D)bicarbonate ion
E)hydrogen phosphate ion

Question 80

Glutamine is metabolised to biocarbonate ion in the ________ to replenish this important component of the blood buffering system.

A)liver
B)kidneys
C)red blood cells
D)muscle tissue