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Biochemistry > Nitrogen Metabolism > Flashcards

Nitrogen Metabolism Flashcards

1
Q

The protein turnover per day is around

A

300 to 400g

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2
Q

What are the possible sources of your amino acids?

A
  1. Degradation and turnover of body protein
  2. Dietary intake
  3. Synthesis of non-essential AA
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3
Q

[Amino Acid Catabolism]

The first phase of AA catabolism is the process called

A

Deamination

Second phase is carbon skeleton of alpha keto acid converted to common intermediates

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4
Q

[Amino Acid Catabolism]

what are the products of deamination?

A
  1. Ammonia

2. corresponding alpha keto acid

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5
Q

[Excretion of amino acids]

What do you call the non-toxic, water soluble urea excreted by land animals

A

ureotolic

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6
Q

[Deamination]

In transamination, the amino acid transfer their amino group to alpha ketoglutarate leading to the formation of what amino acid

A

glutamate

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7
Q

Amino acids that are unable to do transamination?

A
  1. Lysine
  2. Threonine
  3. Proline
  4. Hydroxyproline
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8
Q

[Deamination]

what is the enzyme for transamination?

A

aminotransferase

Coenzyme: pyridoxal phosphate

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9
Q

In alanine aminotransferase, the NH3 is transferred to what ketoacid?

A

alphaketoglutarate

Alanine becomes pyruvate

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10
Q

In aspartate aminotransferase, the NH3 is transferred to ___ to become glutamate

A

alpha ketoglutarate

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11
Q

What enzyme is activated in the oxidative deamination of glutamate?

A

glutamate dehydrogenase

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12
Q

What is the purpose of glutamate dehydrogenase?

A

It oxidizes glutamate to release free ammonia

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13
Q

What is the alpha keto acid counterpart of aspartate?

A

oxaloacetate

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14
Q

In most tissues, glutamate becomes glutamine if it is combined with

A

ammonia

via the enzyme glutamine synthetase

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15
Q

Glutamine is degraded in the body as glutamate and ammonia via the enzyme

A

glutaminase

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16
Q

In the muscle pyruvate can be transaminated to form what amino acid?

A

alanine

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17
Q

Where does urea cycle occur?

A
  1. Liver (both mitochondria and cytosol)
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18
Q

What are the substrates of the urea cycle

A
  1. NH3
  2. Aspartate
  3. CO2
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19
Q

What is the rate limiting step in urea cycle?

A

NH3 + CO2 –> carbamoyl phosphate

Enzyme: carbamoyl phosphate synthetase I

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20
Q

What is the allosteric inhibitor of Carbamoyl Phosphate Synthetase I

A

N-acetylglutamate

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21
Q

[Urea Cycle]

The convesion of CO2 + NH3 to L-ornithine is facilitated by what enzyme?

A

cabramoyl phosphate

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22
Q

[Urea Cycle]

Ornitihine reacts with carbamoyl phosphate to form what intermediate

A

Citrulline

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23
Q

[Urea Cycle]

What amino acid is combined with citrulline to form arginosuccinate

A

aspartate

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24
Q

[Urea Cycle]

What is the byproduct of arginosuccinate cleavage via arginosuccinate lyase?

A
  1. Arginine

2. Fumarate

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25
Q

[Urea Cycle]

What is the last enzyme in urea cycle that yields ariginine and urea

A

Arginase

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26
Q

How many moles of ATP are needed to synthesize 1 mole of urea?

A

2 ATP

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27
Q

[Urea Cycle]

What acts solely as an enzyme activator and regulates urea synthesis?

A

N-acetylglutamate

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28
Q

[Diagnosis]

Tremor, slurring of speech, voimiting, BOV, cerebral edema, somnolence, coma, death

A

hyperammonia

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29
Q

What is the most common enzyme defect in hereditary hyperammonemia?

A
  1. Ornithine transcarbomylase deficieny
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30
Q

What is the most severe form of enzyme deficiency in urea cycle defect?

A

carbamoyl transcarbomylase deficieny

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31
Q

[Diagnose]

hyperammonemia, elevated blood glutamine, decreased BUN, respiratory alkalosis

A

Hereditary Hyperammonemia

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32
Q

What drug is used to convert phenylacetate which binds to glutamin then excreted as phenylglutamine

A

Phenylbutyrate

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33
Q

What metabolites will accumulate in this ornithine cycle deficiency: carbamoyl phosphate I

A

Ammonia

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34
Q

What metabolites will accumulate in this ornithine cycle deficiency: ammonia, orotic acid

A

Ornithine- transcaorboxylase

35
Q

What is the second most common ornithine cycle enzyme deficiency?

A

arginosuccinate synthetase

36
Q

What enzyme is affected if these metabolites accumulate: ammonia, arginosuccinate

A

arginosuccinate lyase

37
Q

What amino acids can be converted back to acetylCoA or acetoacetyl CoA

A

Lysine

Leucine

38
Q

What are you AA that are both glucogenic and ketogenic

A

WIFTY

39
Q

[Synthesis of non essential AA]

alpha ketoglutarate

A

glutamate

40
Q

[Synthesis of non essential AA]

phosphoglycerate

A

serine

41
Q

[Synthesis of non essential AA]

oxaloacetate

A

aspartate

42
Q

[Synthesis of non essential AA]

Serine can become what AA

A
  1. Glycine
43
Q

[Synthesis of non essential AA]

Adding homocysteine to serine can become

A

Cystathionine

44
Q

[Synthesis of non essential AA]

Phenylalanine is a precursor for what AA?

A

Tyrosine

Phenylalanine derivatives:
Tyrosine
L-dopa
Dopa
NE
Epi
45
Q

[Synthesis of non essential AA]

glutamate

A

glutamine

46
Q

[Synthesis of non essential AA]

glutamate semialdehyde

A
  1. Proline

2. Arginine

47
Q

{specialized products of amino acids]

Coenzyme A needs

A

cysteine

48
Q

{specialized products of amino acids]

taurine needs

A

cysteine

49
Q

{specialized products of amino acids]

sphingosine

A

serine

50
Q

S-adenosylmethionine supplies methyl groups to what reactions

A
  1. Guanidoacetate to creatine
  2. Phosphatidylethanolamine to phosphatidylcholine
  3. NE to Epi
  4. Acetylserotonin to melatonin
  5. Polynucleotides to methylated polynucleotides
51
Q

[Catecholamine Syntesis]

Tyrosine to DOPA

A

Tyrosine hydroxylase

52
Q

[Catecholamine Syntesis]

dopa to DOPAMINE

A

DOPA decarboxylase

53
Q

[Catecholamine Syntesis]

what vitamin is needed to convert dopamine to NE

A

Vitamin C

54
Q

[Catecholamine Syntesis]

what mineral is needed to convert dopamine to NE

A

copper

Tyrosinase needs copper

55
Q

What is the excretory form of dopamine?

A

Homovanillic acid

HVA

56
Q

What is the excretory form of NE and Epi?

A

VMA

57
Q

What enzymes degrade catecholamines

A
  1. MAO

2. COMT

58
Q

What catecholamine product is increased in pheochromocytoma?

A

Vanillylmandelic Acid (VMA)

59
Q

[Amino acid disorder]

What enzyme deficiency is present in phenylketonuria

A
  1. Phenylalanine hydroxylase

2. Tetrahydrobiopterin

60
Q

What amino acid becomes essential in phenylketonuria?

A

Tyrosine

61
Q

What gives phenyketonuria its distinct odor?

A

Phenylpyruvate = musty odor

62
Q

[Diagnosis]

mental retardataion, dailure to walk or talk, seizure, fair skin, eczema, musty body ordor

A

phenylketonuria

63
Q

[Amino acid disorder]

What enzyme is deficient in alkaptonuria?

A

homogentisate oxidase

64
Q

What amino acid is degraded by homogentisate oxidase

A

tyrosine

65
Q

[Diagnosis]

dark connective tissues with debilitating arthralgia, urine turns black on standing

A

Alkaptonuria

66
Q

What is responsible for the blackening of the urine in patients with alkaptonuria?

A

Alkapton bodies

Homogentisate is oxidized by polyphenyl oxidase to become bezoquinine acetate = blackening

67
Q

[Diagnose]

absence of pigment from hair, eyes, skin
increased risk for cancer

A

Albinism, lacks tyrosinase

68
Q

[Diagnose]

cabbage like odor, accumulation of fumarulacetoacetate in liver, kidney and nervous system

increased risk for liver CA

A

Tyrosinemia Type I

Defect in fumaryacetoacetate hydrolase

69
Q

[Diagnose]

enzyme affected in tyrosinemia type II

which affects the eyes, skin, mental development

A

tyrosine aminotransferase

70
Q

[Diagnose]

High plasma and urinary levels of homocysteine and methionine, low levels of cystein

A

Homocysteinuria

71
Q

What is the most common deficiency in patients with homocystinuria?

A

cystathionine beta synthase

72
Q

[Diagnose]

Lens displace downward, faulty bone development, osteoporosis

mental retardation
tendency to form thrombi, MI, stroke

A

homocysteinuria

73
Q

What is the enzyme is needed to convert homocysteine to cystein?

A

Cystathionine beta synthase

Coenzyme: pyridoxal phosphate

74
Q

What enzyme is needed to convert homocysteine to methionine?

A

Methionine synthase

Coenzyme: methylcobalamin

75
Q

What amino acid transporters in the PCT are affected in patients with cystinuria?

A
  1. Cystine
  2. Ornithine
  3. Lysine
  4. Arginine
76
Q

[Diagnose]

Excess cystine in the urine, presence of cystine renal stones

A

cystinuria

77
Q

What is the DOC for cystinuria?

A

Acetazolamide to alkalinize the urine

78
Q

Amino acids that are converted to methymalonyl CoA from propionyl CoA

A

VITM

79
Q

[Diagnose]

Siezure, encephalopathy, stroke at age of 1 month to 1 year old

hypotonia, lethargy, failure to thrive, hepatosplenomegaly, monilial infections

A

Methymalonic acidemia

80
Q

The characteristic urine odor of MSUD is due to the?

A

alpha keto acids

81
Q

What enzyme is deficient in patients with MSUD?

A

alpha ketoacid dehydrogenase complex

82
Q

Histidase converts histidine to ____

A

urocanate

83
Q

Waste nitrogen from skeletal AA catabolism is brought to the liver for incorporation into urea by what?

A

Alanine

muscle = mAsel = Alanine

Biochemistry (28 decks)

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