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Biochemistry (Questions) > Question banks for 1st midterm > Flashcards

Question banks for 1st midterm Flashcards

1
Q

Which amino acid is an activator of N-acetyl-glutamate synthase?

Select one:
A. Glutamine
B. Lysine
C. Arginine
D. Aspartate
E. Asparagine

A

C. Arginine

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2
Q

In what form is ammonia transported from muscle to the liver?

Select one:
A. Asparagine
B. Arginine
C. Leucine
D. Glutamine
E. Valine

A

D. glutamine

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3
Q

Which hepatocytes express the highest activity of the ornithine cycle enzymes?

Select one:
A. Periportal
B. Pericentral
C. Perivenous
D. Centrolobular

A

B. pericentral

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4
Q

Which amino acid contributes to the increase in the activity of the sirtuins?

Select one:
A. Tryptophan
B. Phenylalanine
C. Tyrosine
D. Valine
E. Glutamine

A

A. Tryptophan

(it can be used to generate NAD+)

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5
Q

What is the effect of acidosis on the activity of glutamine synthesis in the liver?
Select one:
A. Increase in the periportal hepatocytes
B. Increase in the pericentral hepatocytes
C. Decrease in the perivenous hepatocytes
D. Decrease in all the regions of the lobules

A

B. Increase in the pericentral hepatocytes

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6
Q

Which amino acid does NOT contribute to the formation of pyruvate in the course of its degradation?

A. Alanine
B. Glutamine
C. Tyrosine
D. Leucine
E. Aspartate

A

D. Leucine

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7
Q

Which amino acid can NOT provide any C-atom for the synthesis of glucose in humans?

Select one:
A. Glutamate
B. Isoleucine
C. Leucine
D. Phenylalanine
E. Tryptophan

A

C. Leucine

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8
Q

Which pair of amino acids are released at the highest concentration from skeletal muscle in the fasting state?

Select one:
A. Glutamate, aspartate
B. Glutamine, asparagine
C. Alanine, glutamine
D. Alanine, leucine
E. Valine, leucine

A

C. Alanine, glutamine

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9
Q

What happens in the course of glutaminolysis?
Select one:

A. Glutamine is converted to aspartate
B. Glutamine is converted to asparagine
C. Glutamine is completely oxidized to CO2 and water
D. Glutamine is converted to glucose

A

A. Glutamine is converted to aspartate

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10
Q

Which amino acid is the most common source of the 1C groups transferred by tetrahydrofolate?

Select one:
A. Alanine
B. Serine
C. Threonine
D. Isoleucine
E. Methionine

A

B. Serine

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11
Q

Deficiency of which vitamin would cause enhanced excretion of methylmalonate in the urine?

Select one:
A. B1
B. B2
C. Biotin
D. B12
E. D

A

D. B12

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12
Q

Which amino acids should be enriched in the diet of a patient with phenylketonuria?

Select one:
A. Phe, Gln
B. Arg, Lys
C. Trp, Tyr
D. Asp, Glu
E. Ala, Glu

A

C. Trp, Tyr

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13
Q

Which interconversion includes glutamic semialdehyde as an intermediate?

A. Arginine to Proline
B. Glutamate to Glutamine
C. Glutamate to a-ketoglutarate
D. Methionine to Threonine

A

A. Arginine to Proline

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14
Q

Which vitamin is a co-factor in the synthesis of hydroxyproline?

Select one:
A. B1
B. B2
C. B6
D. B12
E. C

A

E. C

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15
Q

What is the role of Se in the function of the thyroid gland?

Select one:
A. Se participates in the structure of thyroxine
B. Se participates in the structure of thyroglobulin
C. Se participates in the structure of deiodinase
D. Se forms a complex with iodine to activate it for thyroxine synthesis

A

C. Se participate in the structure of deiodinase

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16
Q

How is the nitrogen balance changed, if the food is depleted of Leu, but all other AA are doubled?

Select one:
A. No change
B. Negative N-balance
C. Positive N-balance
D. Positive N-balance only in children
E. Positive N-balance only in adults

A

B. Negative N-balance

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17
Q

How is the nitrogen balance changed, if the food is depleted of Glu, but all other AA are doubled?

Select one:
A. No change
B. Negative N-balance
C. Positive N-balance
D. Negative only in children
E. Positive only in adults

A

A. No change

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18
Q

Dietary supplementation with which AA could counteract the sleep-promoting effect of serotonin?

Select one:
A. Glu
B. Trp
C. Leu
D. Lys
E. Arg

A

C. Leu

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19
Q

Which one is a metalloprotease?

A. Pepsin
B. Trypsin
C. Elastase
D. Carboxypeptidase
E. Chymotrypsin

A

D. Carboxypeptidase

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20
Q

Which zymogen does not need another protease for its activation?

Select one:
A. Trypsinogen
B. Pepsinogen
C. Chymotrypsinogen
D. Proelastase

A

B. Pepsinogen

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21
Q

Which AA is present in the active site of the proteasome proteases?

Select one:
A. Aspartate
B. Tyrosine
C. Lysine
D. Threonine
E. Tryptophan

A

D. Threonine

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22
Q

Which metal ion is present in the active site of the matrix metalloproteases?

Select one:
A. Zn2+
B. Fe2+
C. Fe3+
D. Cu2+
E. Ca2+

A

A. Zn2+

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23
Q

Which AA acts as a signal to suppress autophagy?

Select one:
A. Glycine
B. Leucine
C. Glutamate
D. Glutamine
E. Arginine

A

B. Leucine

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24
Q

Which compound is the first N-free intermediate released in the indirect deamination of aspartate?

Select one:
A. Pyruvate
B. Oxaloacetate
C. Fumarate
D. a-ketoglutarate
E. Methylmalonate

A

C. Fumarate

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25
Q

Which protein kinase is activated to transmit the anabolic signal of insulin?

Select one:
A. PKA
B. AMPK
C. PKC
D. mTOR

A

D. mTOR

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26
Q

Where is hepcidin produced?
Select one:
A. Liver
B. Spleen
C. Intestine
D. Adrenal gland
E. Pancreas

A

A. Liver

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27
Q

What is the normal degree of transferrin saturation with iron?

Select one:
A. 10%
B. 30%
C. 60%
D. 80%
E. 100-120%

A

B. 30%

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28
Q

Which intermediate is elevated in blood in lead poisoning?

Select one:
A. δ-aminolevulinate
B. Protoporphyrin
C. Haem
D. Bilirubin
E. Biliverdin

A

A. δ-aminolevulinate

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29
Q

Which factor regulates the activity of the aminolevulinate synthase 1 (ALAS1)?

Select one:
A. Ferroportin
B. Transferrin receptor 2
C. Haem
D. Iron response element binding protein 1
E. Ferritin

A

C. Haem

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30
Q

Which factor regulates the activity of aminolevulinate synthase 2 (ALAS2)?
Select one:
A. Protoporphyrin
B. Haemoglobin
C. Haem
D. Iron response element binding protein 1
E. Ferroportin

A

D. Iron response element binding protein 1

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31
Q

Which compound is a substrate of haem oxygenase?

Select one:
A. O2
B. CO
C. CO2
D. HCO3-

A

A. O2

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32
Q

Which compound is a product of haem oxygenase?

Select one:
A. CO
B. O2
C. CO2
D. HCO3-
E. NAPDH

A

A. CO

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33
Q

Why is blue light used to treat neonatal icterus?

Select one:
A. Blue light promotes the conjugation of bilirubin
B. Blue light activates the haem oxygenase in the skin
C. Blue light generates lipid-soluble photoisomers of bilirubin
D. Blue light generates photoisomers of bilirubin with higher water
solubility

A

D. Blue light generates photoisomers of bilirubin with higher water solubility

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34
Q

In what form do the dietary purine bases enter the blood circulation?

Select one:
A. Nucleotide
B. Nucleoside
C. Free base
D. Uric acid

A

D. Uric acid

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35
Q

Which enzyme is needed for the salvage of purine bases?

Select one:
A. Phosphoribosyl-pyrophosphate synthetase
B. Xanthine oxidase
C. Xanthine dehydrogenase
D. AMP deaminase

A

A. Phosphoribosyl- pyrophosphate synthetase

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36
Q

Which two amino acids contribute with 2 N atoms each to the de novo synthesis of one adenine?

Select one:
A. Asparagine, Glutamine
B. Aspartate, Glutamine
C. Asparagine, Glutamate
D. Aspartate, Glutamate

A

B. Aspartate, Glutamine

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37
Q

Which amino acid contributes with both C and N atoms to the de novo syntheses of adenine?

Select one:
A. Glycine
B. Glutamine
C. Aspartate
D. Tryptophan

A

A. Glycine

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38
Q

The degradation of which nucleotide generates propionyl-CoA?

Select one:
A. AMP
B. GMP
C. UMP
D. TMP

A

D. TMP

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39
Q

Which amino acid contributes with 4 atoms to the de-novo synthesis of one pyrimidine ring?

Select one:
A. Glycine
B. Proline
C. Aspartate
D. Proline

A

C. Aspartate

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40
Q

Which compound is a substrate of the ribonucleotide reductase?

Select 1:
A. AMP
B. ADP
C. ATP
D. Phosphoribosyl-pyrophosphate

A

B. ADP

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41
Q

Identify the following amino acid

A

Glycine

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42
Q

Identify the following amino acid

A

Aspartic acid

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43
Q

Identify the following amino acid:

A

Asparagine

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44
Q

Identify the following amino acid:

A

Glutamic acid

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45
Q

Identify the following amino acid:

A

Glutamine

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46
Q

Identify the following amino acid:

A

Arginine

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47
Q

Identify the following amino acid:

A

Lysine

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48
Q

Identify the following amino acid:

A

Histidine

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49
Q

Identify the following amino acid:

A

Phenylalanine

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50
Q

Identify the following amino acid:

A

Tyrosine

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51
Q

Identify the following amino acid:

A

Tryptophan

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52
Q

Identify the following amino acid:

A

Glycine

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53
Q

Identify the following amino acid:

A

Proline

54
Q

Identify the following amino acid:

A

Valine

55
Q

Identify the following amino acid:

A

Leucine

56
Q

Identify the following amino acid:

A

Isoleucine

57
Q

Identify the following amino acid:

A

Serine

58
Q

Identify the following amino acid:

A

Threonine

59
Q

Identify the following amino acid:

A

Cysteine

60
Q

Identify the following amino acid:

A

Methionine

61
Q

Select all the valid statements (one or more)

A. In the course of the urea cycle fumarate is produced
B. Enzymes of the urea cycle participate in the de novo synthesis of arginine
C. The amide group of glutamine serves as nitrogen source for the N-
acetylglutamate-activated carbamoylphosphate synthetase
D. Ornithine can be synthesized from glutamate

A

A. In the course of the urea cycle fumarate is produced
B. Enzymes of the urea cycle participate in the de novo synthesis of arginine
D. Ornithine can be synthesized from glutamate

62
Q

Select all the valid statements (one or more)

A. Citrullin is an intermediate of the urea cycle
B. Citrullin is a precursor of the de novo arginine biosynthesis
C. Urea may be produced by the kidney
D. Arginine may be produced by the kidney

A

A. Citrullin is an intermediate of the urea cycle
B. Citrullin is a precursor of the de novo arginine biosynthesis
D. Arginine may be produced by the kidney

63
Q

Select the false statement

Select one:
A. Urea can be produced by the kidney
B. The nitrogen atoms present in urea are derived from free ammonium
ion and from aspartate
C. The de novo synthesis of arginine requires ornithine synthesis
D. Ornithine is synthesized from glutamate
E. Arginine may be produced in the kidney

A

A. Urea can be produced by the kidney

64
Q

A part of the carbon skeleton of which amino acids may enter the citric acid cycle in the form of succinyl-CoA?

Select one or more:
A. Isoleucine
B. Leucine
C. Tyrosine
D. Proline
E. Valine

A

A. Isoleucine
E. Valine

65
Q

A part of the carbon skeleton of which amino acids may enter the citric acid cycle in the form of a-ketoglutarate?

Select one or more:
A. Proline
B. Glutamine
C. Arginine
D. Cysteine
E. Phenylalanine

A

A. Proline
B. Glutamine
C. Arginin

66
Q

A part of the carbon skeleton of which amino acids may enter the citric acid cycle?

Select one or more:
A. Leucine
B. Asparagine
C. Phenylalanine
D. Tyrosine

A

B. Asparagine
C. Phenylalanine
D. Tyrosine

67
Q

Which of the following answer(s) complete(s) the sentence correctly?

Glutamate is reduced to glutamic semialdehyde in the course of the formation of…

Select one or more:
A. Ornithine
B. Proline
C. Glutamine
D. Glutathione
E. G-aminobutyrate

A

A. Ornithine
B. Proline

68
Q

Select all valid statements (one or more):

A. Formation of tyrosine is an essential step in the physiological degradation of phenylalanine
B. Degradation of phenylalanine starts with removal of the amino group by phenylalanine a-ketoglutarate transaminase
C. The carbon skeleton of phenylalanine yields acetoacetate

A

A. Formation of tyrosine is an essential step in the physiological degradation of phenylalanine
C. The carbon skeleton of phenylalanine yields acetoacetate

69
Q

Select all valid statements (one or more):

A. Formation of tyrosine is an essential step in the physiological degradation of phenylalanine
B. Phenylalanine may lose its amino group by a phenylalanine a- ketoglutarate transaminase under pathological conditions
C. Carbon skeleton of phenylalanine yields acetoacetate

A

A. Formation of tyrosine is an essential step in the physiological degradation of phenylalanine
B. Phenylalanine may lose its amino group by a phenylalanine a- ketoglutarate transaminase under pathological conditions
C. Carbon skeleton of phenylalanine yields acetoacetate

70
Q

Select all the valid statements (one or more):

A. Folic acid should be reduced in order to serve as a one carbon carrier
B. S-adenosylmethionine is a methyl-group donor
C. Regeneration of S-adenosylmethionine from S-adenosylhomocysteine requires B12 vitamin
D. One carbon unit carried by the derivative of folic acid are derived from S-adenosylmethionine

A

A. Folic acid should be reduced in order to serve as a one carbon carrier
B. S-adenosylmethionine is a methyl-group donor
C. Regeneration of S-adenosylmethionine from S-adenosylhomocysteine requires B12 vitamin

71
Q

Select all valid statements (one or more):

A. One carbon unit carried by tetrahydrofolic acid may be derived from serine, glycine, tryptophan or histidine
B. All one carbon units bound by tetrahydrofolic acid can be transformed into each other
C. The methyl group carried by tetrahydrofolic acid is derived from methionine

A

One carbon unit carried by tetrahydrofolic acid may be derived from serine, glycine, tryptophan or histidine

(is more versatile than the other cofactors in that it functions to transfer C1 units
in several oxidation states.)

72
Q

Which of the following amino acid are nutritionally essential for the human organism?

Select one or more:
A. Proline
B. Valine
C. Phenylalanine
D. Methionine
E. Cysteine

A

B. Valine
C. Phenylalanine
D. Methionine

73
Q

Which of the following amino acids are nutritionally non-essential for the human organism?

Select one or more:
A. Proline
B. Valine
C. Tyrosine
D. Methionine
E. Cysteine

A

A. Proline
C. Tyrosine
E. Cysteine

74
Q

Which of the following amino acids are nutritionally essential for the human organism?

Select one or more:
A. Isoleucine
B. Serine
C. Cysteine
D. Phenylalanine
E. Tryptophan

A

A. Isoleucine
D. Phenylalanine
E. Tryptophan

75
Q

Select the enzymes which can directly catalyze the release of ammonia

Select one or more:
A. Glutaminase
B. Glutamate dehydrogenase
C. Isoleucine-a-ketoglutarate aminotransferase
D. Arginase
E. Mitochondrial carbamoylphosphate synthetase

A

A. Glutaminase
B. Glutamate dehydrogenase

76
Q

Select those enzymes which can incorporate free ammonia (from ammonium ion) into organic compounds!

Select one or more:
a. Glutamine synthetase
b. Glutamate dehydrogenase
c. Mitochondrial carbamoylphosphate synthetase
d. Arginosuccinate lyase
e. Asparagine synthetase

A

a. Glutamine synthetase
b. Glutamate dehydrogenase
c. Mitochondrial carbamoylphosphate synthetase

77
Q

Select the false statement!

Select one:
a. Aspartate is a nitrogen donor in the course of urea formation
b. One of the nitrogen atoms of urea is derived from free ammonia
c. The amide group of glutamines is removed by glutamate dehydrogenase
d. The amino group of alanine may be released as free ammonia in a series of two consecutive reactions
e. The transaminase reactions require pyridoxal phosphate

A

c. The amide group of glutamines is removed by glutamate dehydrogenase

78
Q

Which of the following reactions, enzymes or compounds participate in the urea cycle?

Select one or more:
a. synthesis of carbamoyl phosphate
b. aspartate
c. formation of argininosuccinate
d. ornithine
e. arginase

A

a. synthesis of carbamoyl phosphate
b. aspartate
c. formation of argininosuccinate
d. ornithine
e. arginase

79
Q

Phenylketonuria can be a consequence of

Select one or more:
a. dihydrobiopterin reductase deficiency
b. vitamin B6 deficiency
c. phenylalanine hydroxylase deficiency
d. defective synthesis of biopterin
e. vitamin C deficiency

A

a. dihydrobiopterin reductase deficiency
c. phenylalanine hydroxylase deficiency
d. defective synthesis of biopterin

80
Q

Which of the urea cycle enzymes are not localized in the cytosol?

Select one or more:
a. carbamoyl phosphate synthetase I
b. ornithine transcarbamoylase
c. argininosuccinate lyase
d. argininosuccinate synthetase
e. arginase

A

a. carbamoyl phosphate synthetase I
b. ornithine transcarbamoylase

81
Q

What is the fate of the exocytosed glutamic acid localized in the synaptic cleft?

Select one or more:
a. Glutamate can enter into the postsynaptic neuron by ionotropic receptors
b. Glutamate dehydrogenase splits the molecule in the synaptic cleft, the formed alfa-ketoglutarate is taken up by the postsynaptic neuron
c. Most of glutamate is taken up by astrocytes at the expense of Na+ gradient.
d. Glutamate is transformed into glutamine in astrocytes
e. Released glutamate will be recycled to the neurons in the form of glutamine

A

c. Most of glutamate is taken up by astrocytes at the expense of Na+ gradient.
d. Glutamate is transformed into glutamine in astrocytes
e. Released glutamate will be recycled to the neurons in the form of glutamine

82
Q

Which of the following statements is/are true for the digestive enzymes?

Select one or more:
a. The carboxypeptidase is a carboxyl protease
b. Elastase and pepsin are thiol proteases
c. No Zn2+ protease can be found in the gastrointestinal tract
d. Both trypsin and chymotrypsin are serine proteases.

A

d. Both trypsin and chymotrypsin are serine proteases.

83
Q

Which of the following agents and enzymes are required for the synthesis of cysteine?

Select one or more:
a. methionine
b. adenosyl homocysteinase
c. serine
d. cystathionine synthase
e. cystathionase

A

a. methionine
b. adenosyl homocysteinase
c. serine
d. cystathionine synthase
e. cystathionase

84
Q

Which of the following statements are valid for transamination?

Select one or more:
a. It is a reversible reaction
b. The coenzyme of transaminases is a noncovalently bound cobalamin
c. In the first step of catalysis ketoacids are attached to the lysine residue of the enzyme forming a Schiff base
d. The Schiff base linkage is in tautomeric equilibrium between an aldimine and a ketamine.

A

a. It is a reversible reaction
d. The Schiff base linkage is in tautomeric equilibrium between an aldimine and a ketamine.

85
Q

Tetrahydrofolate has the following one-carbon derivatives:

Select one or more:

a. methyl H4folate
b. methylene H4folate
c. methenyl H4folate
d. carboxyl H4folate

A

a. methyl H4folate
b. methylene H4folate
c. methenyl H4folate

86
Q

S Adenosylmethionine (SAM) is the methyl donor in the synthesis of

Select one or more:
a. carnitine
b. epinephrine
c. choline
d. norepinephrine

A

a. carnitine
b. epinephrine
c. choline

87
Q

S Adenosylmethionine (SAM) is the methyl donor in the synthesis of

Select one or more:
a. urea
b. methyl-malonyl-CoA
c. choline
d. epinephrine

A

c. choline
d. epinephrine

88
Q

Transamination of the following amino acids results in formation of citric acid cycle intermediates
Select one or more:

a. lysine
b. aspartate
c. leucine
d. glutamate

A

b. aspartate
d. glutamate

89
Q

Degradation of the following amino acids results in formation of citric acid cycle intermediates

Select one or more:
a. valine
b. leucine
c. isoleucine
d. tryptophane

A

a. valine
c. isoleucine

90
Q

Which of the following amino acids are ketoplastic?

Select one or more:
a. serine
b. leucine
c. Cysteine
d. lysine

A

b. leucine
d. lysine

(A ketogenic amino acid is an amino acid that can be degraded directly into acetyl-CoA)

91
Q

The reaction catalysed by the mitochondrial carbamoyl phosphate synthetase

Select one or more:
a. uses 2 ATP molecules
b. uses glutamine as a substrate
c. inhibited by N-acetylglutamate
d. activated by N-acetylglutamate

A

a. uses 2 ATP molecules
d. activated by N- acetylglutamate

92
Q

Which of the following statements are true for the urea cycle?

Select one or more:
a. A citric acid cycle intermediate is formed in the cycle
b. The enzymes of the cycle are located either in the cytosol or in the mitochondria
c. Condensation of citrulline and glutamate requires hydrolysis of ATP
d. Synthesis of one urea molecule consumes energy equivalent to three high group transfer potential bonds

A

a. A citric acid cycle intermediate is formed in the cycle
b. The enzymes of the cycle are located either in the cytosol or in the mitochondria

93
Q

Synthesis of tyrosine requires

Select one or more:
a. dietary phenylalanine
b. phenylalanine hydroxylase
c. tetrahydrobiopterin
d. dihydrobiopteridine reductase
e. transamination of phenylalanine

A

a. dietary phenylalanine
b. phenylalanine hydroxylase
c. tetrahydrobiopterin
d. dihydrobiopteridine reductase

94
Q

Synthesis of proline involves
Select one or more:

a. glutamate
b. N-methyl-lysine
c. pyrroline-5-carboxylate reductase
d. glutamic semialdehyde
e. pyrroline-5-carboxylate

A

a. glutamate
b. N-methyl-lysine
c. pyrroline-5-carboxylate reductase
d. glutamic semialdehyde
e. pyrroline-5-carboxylate

(The initial reaction of proline biosynthesis converts the γ-carboxyl group of glutamate to the mixed acid anhydride of glutamate γ-phosphate (Figure 27-3). Subsequent reduction forms glutamate γ-semialdehyde, which following spontaneous cyclization is reduced to l-proline (Figure 27–10).)

95
Q

Tryptophan can be the precursor of the following compounds:

Select one or more:
a. Lysine
b. acetoacetyl-CoA
c. nicotinamide
d. alanine
e. serotonin

A

b. acetoacetyl-CoA
c. nicotinamide
d. alanine
e. serotonin

96
Q

Which of the following enzymes are regulated by N-acetylglutamate?

Select one:
a. N-acetylglutamate synthase
b. Ornithine transcarbamoylase
c. Carbamoyl phosphate synthetase I
d. Carbamoyl phosphate synthetase II
e. Arginase

A

c. Carbamoyl phosphate synthetase I

97
Q

Which of the following parameters are suitable to differentiate the deficiency of carbamoyl phosphate synthetase I and ornithine transcarbamoylase?

Select one:
a. Determination of blood pH
b. Determination of citrulline level in blood
c. Determination of arginine level in plasma
d. Determination of orotic acid level in urine
e. Determination of ammonia level in blood

A

d. Determination of orotic acid level in urine

98
Q

Patients with deficiency of carbamoyl phosphate synthetase I and ornithine transcarbamoylase are treated with sodium benzoate and sodium phenylacetate. What is the rationale of this treatment?

Select one or more:
a. Benzoate conjugates with Gly and removes 1 N atom
b. Phenylacetate conjugates with Hippurate and removes 1 N atom
c. Benzoate and phenylacetate activate the enzymes of urea cycle
d. Phenylacetate conjugates with glutamine and removes 2 N atoms
e. N- containing conjugation products of benzoate and phenylacetate are released in the urine

A

a. Benzoate conjugates with Gly and removes 1 N atom
b. Phenylacetate conjugates with Hippurate and removes 1 N atom
e. N- containing conjugation products of benzoate and phenylacetate are released in the urine

99
Q

Which of the following intermediates can be converted to serine in a single step reaction?

Select one:
a. Pyruvate
b. Some citric acid cycle intermediates
c. Some ornithine cycle intermediates
d. Glycine
e. Choline

A

d. Glycine

100
Q

Which of the following amino acids are non-essential for an adult human?

Select one or more:
a. Phe
b. Tyr
c. Met
d. Cys
e. Glu

A

b. Tyr
d. Cys
e. Glu

101
Q

Which of the following proteases is/are involved in the activation of pancreatic proenzymes?

Select one or more:
a. Carboxypeptidase A
b. Enteropeptidase
c. Trypsin
d. Chymotrypsin
e. Elastase

A

b. Enteropeptidase
c. Trypsin

102
Q

Which of the following statements are valid for aminotransferases (AT)? The AT needs:

Select one or more:
a. Efficient amount of Vitamin B6
b. The presence of free amino acids
c. The presence of free ketoacids
d. The formation of Schiff base between the amino group of the amino acid and aldehyde group of pyridoxal phosphate
e. The presence of AT in blood circulation

A

a. Efficient amount of Vitamin B6
b. The presence of free amino acids
c. The presence of free ketoacids
d. The formation of Schiff base between the amino group of the amino acid and aldehyde group of pyridoxal phosphate

103
Q

Which of the following statements are valid for the S-adenosylmethionine cycle?

Select one or more:
a. Met + ATP forms S-adenosylmethionine
b. Stable covalent bond exists between one C atom of Met and 5’C atom of adenosine
c. S-adenosylmethionine is converted to homocysteine + H2O
d. Homocysteine+ N5-Methyl FH4 form Met + FH4
e. Homocysteine methyltransferase uses a vitamin B12 derived cofactor

A

a. Met + ATP forms S- adenosylmethionine
d. Homocysteine+ N5-Methyl FH4 form Met + FH4
e. Homocysteine methyltransferase uses a vitamin B12 derived cofactor

104
Q

Which of the following amino acids have their alpha-amino groups removed by dehydratases?

Select one or more:
a. Histidine
b. Tryptophan
c. Serine
d. Glutamine
e. Threonine

A

c. Serine
e. Threonine

105
Q

Which of the following amino acids are derived from alpha-ketoglutarate?

Select one or more:
a. Glutamate
b. Cysteine
c. Aspartate
d. Proline
e. Serine

A

a. Glutamate
d. Proline

106
Q

Which of the following statements are valid for N-acetyl-glutamate?

Select one or more:
a. its concentration depends on the concentration of arginine
b. its concentration depends on the concentration of ornithine
c. it is an activator of carbamoyl phosphate synthetase I
d. it is an inhibitor of argininosuccinate lyase
e. it is an activator of ornithine transcarbamoylase

A

a. its concentration depends on the concentration of arginine
c. it is an activator of carbamoyl phosphate synthetase I

107
Q

Hyperhomocysteinemia can be the consequence of:

Select one or more:
a. cystathionine -synthase deficiency
b. methylene tetrahydrofolate reductase deficiency
c. folate deficiency
d. B12 deficiency
e. methionine deficiency

A

a. cystathionine -synthase deficiency
b. methylene tetrahydrofolate reductase deficiency
c. folate deficiency
d. B12 deficiency

108
Q

High citrulline levels are characteristic in the following enzyme deficiencies:

Select one or more:
a. carbamoyl phosphate synthetase
b. arginino succinate synthetase
c. arginino succinase
d. ornithine transcarbamoylase

A

b. arginino succinate synthetase
c. arginino succinase

109
Q

Which enzyme is critical in the activation of zymogens for the digestion of proteins in the small intestine?

Select one:
a. enteropeptidase
b. hexokinase
c. papain
d. pepsin
e. secretin

A

a. enteropeptidase

110
Q

Which of these is NOT an intestinal protease?
Select one:
a. chymotrypsin
b. elastase
c. enteropeptidase
d. pepsin
e. trypsin

A

d. pepsin

111
Q

Which of the following is a zymogen that can be converted to an endopeptidase that hydrolyses peptide bonds adjacent to Lys and Arg residues?

Select one:
a. Chymotrypsinogen
b. pepsin
c. pepsinogen
d. Proelastase
e. trypsinogen

A

e. trypsinogen

112
Q

In amino acid catabolism, the first reaction for many amino acids is a:

Select one:
a. decarboxylation requiring thiamine pyrophosphate (TPP). b. hydroxylation requiring NADPH and O2.
c. oxidative deamination requiring NAD+.
d. reduction requiring pyridoxal phosphate (PLP).
e. transamination requiring pyridoxal phosphate.

A

e. transamination requiring pyridoxal phosphate.

113
Q

The cofactor required for all transaminations is derived from:

Select one:
a. niacin.
b. pyridoxine (vitamin B6).
c. riboflavin
d. thiamine.
e. vitamin B12

A

b. pyridoxine (vitamin B6).

114
Q

The cofactor involved in a transaminase reaction is:

Select one:
a. biotin phosphate.
b. lipoic acid.
c. nicotinamide adenine dinucleotide phosphate (NADP+). d. pyridoxal phosphate (PLP)
e. thiamine pyrophosphate (TPP).

A

d. pyridoxal phosphate (PLP)

115
Q

Transamination of alanine to alpha-ketoglutarate requires the cofactor:

Select one:
a. thiamine pyrophosphate (TPP).
b. pyridoxal phosphate (PLP).
c. No coenzyme is involved.
d. NADH.
e. biotin.

A

b. pyridoxal phosphate (PLP).

116
Q

Pyridoxal phosphate is a cofactor in this class of reactions:

Select one:
a. transamination.
b. reduction.
c. methylation.
d. desulfuration.
e. acetylation.

A

a. transamination.

117
Q

Which of the following is not true for the reaction catalyzed by glutamate dehydrogenase?

Select one:
a. The reaction is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP).
b. The enzyme is specific for glutamate.
c. The enzyme can use either NAD+ or NADP+ as a cofactor.
d. NH4+ is produced.
e. alpha-ketoglutarate is produced

A

a. The reaction is similar to transamination in that it involves the coenzyme pyridoxal phosphate (PLP).

118
Q

Glutamate is metabolically converted to alpha-ketoglutarate and NH4+ by a process described as:

Select one:
a. transamination.
b. reductive deamination.
c. hydrolysis.
d. deamidation
e. oxidative deamination

A

e. oxidative deamination

119
Q

The conversion of glutamate to an alpha-ketoacid and NH4+:

Select one:
a. does not require any cofactors.
b. is a reductive deamination.
c. is accompanied by ATP hydrolysis catalyzed by the same enzyme.
d. is catalyzed by glutamate dehydrogenase.
e. requires ATP.

A

d. is catalyzed by glutamate dehydrogenase.

120
Q

Which substance is NOT involved in the production of urea from NH4+ via the urea cycle?

Select one:
a. ornithine
b. malate
c. carbamoyl phosphate
d. ATP
e. aspartate

A

b. malate

121
Q

A nitrogen atom of which compound is incorporated in the urea by an enzyme of the urea cycle?

Select one:
a. ornithine
b. glutamate
c. carnitine
d. aspartate
e. adenine

A

d. aspartate

122
Q

Conversion of ornithine to citrulline is a step in the synthesis of:

Select one:
a. urea.
b. tyrosine.
c. pyruvate.
d. carnitine.
e. aspartate.

A

a. urea

123
Q

In the urea cycle, ornithine transcarbamoylase catalyzes:

Select one:
a. cleavage of urea to ammonia.
b. formation of citrulline from ornithine and another reactant.
c. formation of ornithine from citrulline and another reactant.
d. formation of urea from arginine.
e. transamination of arginine

A

b. formation of citrulline from ornithine and another reactant.

124
Q

The amino acids serine, alanine, and cysteine can be catabolized to yield:

Select one:
a. succinate.
b. pyruvate.
c. oxaloacetate
d. fumarate.
e. alpha-ketoglutarate.

A

b. pyruvate.

125
Q

Serine or cysteine may enter the citric acid cycle as acetyl-CoA after conversion to:

Select one:
a. oxaloacetate.
b. propionate.
c. pyruvate.
d. succinate.
e. succinyl-CoA.

A

c. pyruvate.

126
Q

The human genetic disease phenylketonuria (PKU) can result from:

Select one:
a. inability to convert phenylalanine to tyrosine.
b. deficiency of protein in the diet.
c. inability to catabolize ketone bodies.
d. inability to synthesize phenylalanine.
e. production of enzymes containing no phenylalanine.

A

a. inability to convert phenylalanine to tyrosine.

127
Q

Nonessential amino acids:

Select one:
a. may be substituted with other amino acids in proteins.
b. can be synthesized in humans.
c. are synthesized by plants and bacteria, but not by humans.
d. are not utilized in mammalian proteins.
e. cannot be converted to intermediates of the citric acid cycle.

A

b. can be synthesized in humans.

128
Q

Glutamine, arginine, and proline:

Select one:
a. do not have a common precursor in their synthesis
b. may all be derived from a citric acid cycle intermediate.
c. may all be derived from a glycolytic intermediate.
d. may all be derived from a urea cycle intermediate.

A

b. may all be derived from a citric acid cycle intermediate.

129
Q

Delta-aminolaevulinic acid is formed from succinyl-CoA and __________ and is an intermediate in the biosynthesis of _________.

Select one:
a. serine; sphingosine
b. serine; heme
c. acetyl-CoA; long chain fatty acids
d. alpha-ketoglutarate; glutamate and proline
e. glycine; porphyrin

A

e. glycine; porphyrin

130
Q

Glutathione is a:

Select one:
a. product of glutamate and methionine.
b. tripeptide of glycine, glutamate, and cysteine.
c. enzyme essential in the synthesis of glutamate.
d. methyl-group donor in many biosynthetic pathways.

A

b. tripeptide of glycine, glutamate, and cysteine.

131
Q

Which amino acid is not directly involved in the purine biosynthetic pathway?

Select one:
a. alanine.
b. aspartate.
c. glutamine.
d. glycine.

A

a. alanine.

132
Q

Which of the amino acids below have a small polar side chain containing a hydroxyl group?
Select one or more:

a. Glycine
b. Serine
c. Threonine
d. Lysine
e. Leucine

A

c. Threonine

Biochemistry (Questions) (35 decks)

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