Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry > The Metabolism of Nitrogen > Flashcards

The Metabolism of Nitrogen Flashcards

1
Q

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

A

c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

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.

A

c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

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

A

c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

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.

A

e

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

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

A

b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How many ATP are required for the production of two ammonia molecules (NH3) from one nitrogen molecule (N2)?
a. 2 ATP.
b. 4 ATP.
c. 8 ATP.
d. 16 ATP.
e. 32 ATP.

A

d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which of the following is not a component of the nitrogenase complex?
a. a molybdenum complex
b. a nonheme iron-sulfur protein (Fe protein)
c. ferredoxin
d. pyridoxal phosphate

A

d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

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.

A

d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

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

A

b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

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

A

b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

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

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

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

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Glycine, alanine, serine, histidine, tryptophan, CTP, AMP, and carbamoyl-phosphate all have what in common?
a. They are all inhibitors of glutamine synthase
b. They are all amino acids
c. They are all cofactors in transamination reactions
d. They are activators of the urea cycle

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

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

A

d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

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

A

b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

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

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

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

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

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

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

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

A

b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

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

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

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

A

c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

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

A

c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

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

A

e

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

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

A

c

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

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

A

b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

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.

A

d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

In animals, the synthesis of cysteine involves all of the following, except:
a. Addition of a carbon group to glycine.
b. Transfer of the sulfur group from methionine.
c. An intermediate of homocysteine.
d. Participation of ATP.
e. All of these reactions are involved in synthesizing cysteine in animals.

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

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

A

b

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

There is a curious diversity of nature for the two sulfur containing amino acids. Methionine is made from cysteine in bacteria, but cysteine is made from methionine in mammals.
a. True
b. False

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

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.

A

d

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

Which of the following are all essential amino acids in humans?
a. leucine, lysine, valine
b. methionine, threonine, serine
c. arginine, histidine, cysteine
d. glutamate, glutamine, arginine
e. valine, isoleucine, glycine

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

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

A

a

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
34
Q

Some amino acids can only be made in small quantities in humans and must be supplemented in the diet in children or
during repair of injured tissue.
a. True
b. False

A

a

35
Q

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

A

a

36
Q

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

A

b

37
Q
  1. Which group of small molecules best fit the boxes associated with the reaction shown?

(picture)

  A                            B I. 2 ATP                 2 ADP + Pi II. ATP                     AMP + Pi III. ATP                        ADP IV. NADPH               NADP+
A

a

38
Q

Which of the following statements concerning arginine is true?
a. Arginine is only marginally an essential amino acid, since it is made in the urea cycle.
b. Aspartic acid is the main amino acid precursor for the carbon chain in arginine.
c. Lysine could substitute for arginine as a dietary source for arginine.
d. Arginine is only essential in adults

A

a

39
Q

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

A

c

40
Q

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

A

d

41
Q

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

A

a

42
Q

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

A

c

43
Q

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.

A

d

44
Q

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.

A

c

45
Q

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.

A

d

46
Q

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.

A

d

47
Q

If an amino acid is ketogenic, then it:
a. has a catabolic pathway that leads to acetyl-CoA or acetoacetyl-CoA
b. has a one step pathway to a fatty acid
c. enters the citric acid cycle as pyruvate
d. enters the citric acid cycle as fumarate
e. none of these

A

a

48
Q

The form in which nitrogen waste is removed from the body is dependent mostly on the organism’s availability of
water.
a. True
b. False

A

a

49
Q

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

A

c

50
Q

If an amino acid’s degradation pathway leads to α-ketoglutarate, is it glucogenic?
a. Yes.
b. No.
c. Only if the organism has a glyoxylate pathway.
d. Only if the organism does not have a glyoxylate pathway.

A

a

51
Q

High protein foods are not advisable for the long distance runner during a race because they increase the need for
water and for urination.
a. True
b. False

A

a

52
Q

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

A

d

53
Q

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

A

b

54
Q

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.

A

d

55
Q

How is cancer chemotherapy related to purine biosyntheis?
a. rapidly dividing cells require more purine biosynthesis and some chemotherapy drugs inhibit a key enzyme in purine biosynthesis
b. aminopterin is a good chemotherapy drug because it inhibits aspartate transcarbamoylase
c. cancer cells lack folic acid, and chemotherapy drugs like sulfanamide act by overproducing folic acid, which is
then poisonous to the cancer cells
d. none of these

A

a

56
Q

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

A

d

57
Q

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.

A

c

58
Q

What intermediate of the TCA cycle is produced from aspartic acid during the urea cycle, synthesis of IMP, and conversion from IMP to adenosine?
a. fumarate
b. malate
c. α-ketoglutarate
d. succinate

A

a

59
Q

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

A

b

60
Q

Purine salvage reactions
a. use bases as the substrate
b. use nucleosides as the substrate
c. produce nucleosides as products
d. require the hydrolysis of ATP
e. none of these

A

a

61
Q

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

A

a

62
Q

The energy costs for synthesizing the bases for RNA and DNA is so high that salvage pathways have been developed
to recycle existing bases and nucleotides.
a. True
b. False

A

a

63
Q

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

A

b

64
Q

One way in which the anabolism of pyrimidine nucleotides differs from that of purine nucleotides is that
a. the pyrimidine ring is assembled before being bonded to the ribose phosphate, whereas the purine ring is
bonded to the ribose phosphate as it is formed
b. there is no feedback inhibition in the anabolism of pyrimidine nucleotides, while feedback inhibition is
important in the synthesis of purine nucleotides
c. glycine appears in the pathway for formation of pyrimidine nucleotides but not in that for the formation of
purine nucleotides
d. argininosuccinate is a key intermediate in pyrimidine biosynthesis

A

a

65
Q

Which of the following is not associated with pyrimidine synthesis?
a. Synthesis of the base while ribose is attached.
b. Stimulation of synthesis by purines.
c. An orotic acid intermediate.
d. Inhibition by pyrimidines.
e. All of these are features of pyrimidine synthesis.

A

a

66
Q

Carbamoyl phosphate is made in both the mitochondria and the cytosol, because it is used in the synthesis of several
different molecules which are made in either of the compartments.
a. True
b. False

A

a

67
Q

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

A

c

68
Q

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

A

c

69
Q

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.

A

c

70
Q

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

A

d

71
Q

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

A

d

72
Q

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.

A

b

73
Q

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

A

b

74
Q

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

A

c

75
Q

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

A

b

76
Q

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

A

b

77
Q

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

A

d

78
Q

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.

A

e

79
Q

Identify the half reaction of the reduction of molecular nitrogen to an ammonium ion.

a. N2 + 8e + 14ATP + 10H → 2NH4 + 14ADP + 16Pi + H2

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

c. N2 + 8e + 12ATP + 10H → 2NH4 + 12ADP + 16Pi + H2

c. N2 + 8e + 10ATP + 10H → 2NH4 + 10ADP + 16Pi + H2

A

b

80
Q

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

A

d

81
Q

Explain the importance of the feedback inhibition mechanism in nitrogen metabolism.

A

The biosynthesis pathways that produce amino acids and the bases of nucleotides are long and
complex. They require a large investment of energy by the organism. If there is a high level of an
end product, such as an amino acid or a nucleotide, the cells of the organism save energy by halting
the production of that compound. However, the cells need a signal to tell it to stop producing more
of that particular product. The signal is frequently part of a feedback inhibition mechanism.

82
Q

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

A

c

83
Q

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

A

a

Biochemistry (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions