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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
[Urea Cycle] What is the last enzyme in urea cycle that yields ariginine and urea
Arginase
26
How many moles of ATP are needed to synthesize 1 mole of urea?
2 ATP
27
[Urea Cycle] What acts solely as an enzyme activator and regulates urea synthesis?
N-acetylglutamate
28
[Diagnosis] Tremor, slurring of speech, voimiting, BOV, cerebral edema, somnolence, coma, death
hyperammonia
29
What is the most common enzyme defect in hereditary hyperammonemia?
1. Ornithine transcarbomylase deficieny
30
What is the most severe form of enzyme deficiency in urea cycle defect?
carbamoyl transcarbomylase deficieny
31
[Diagnose] hyperammonemia, elevated blood glutamine, decreased BUN, respiratory alkalosis
Hereditary Hyperammonemia
32
What drug is used to convert phenylacetate which binds to glutamin then excreted as phenylglutamine
Phenylbutyrate
33
What metabolites will accumulate in this ornithine cycle deficiency: carbamoyl phosphate I
Ammonia
34
What metabolites will accumulate in this ornithine cycle deficiency: ammonia, orotic acid
Ornithine- transcaorboxylase
35
What is the second most common ornithine cycle enzyme deficiency?
arginosuccinate synthetase
36
What enzyme is affected if these metabolites accumulate: ammonia, arginosuccinate
arginosuccinate lyase
37
What amino acids can be converted back to acetylCoA or acetoacetyl CoA
Lysine | Leucine
38
What are you AA that are both glucogenic and ketogenic
WIFTY
39
[Synthesis of non essential AA] alpha ketoglutarate
glutamate
40
[Synthesis of non essential AA] phosphoglycerate
serine
41
[Synthesis of non essential AA] oxaloacetate
aspartate
42
[Synthesis of non essential AA] Serine can become what AA
1. Glycine
43
[Synthesis of non essential AA] Adding homocysteine to serine can become
Cystathionine
44
[Synthesis of non essential AA] Phenylalanine is a precursor for what AA?
Tyrosine ``` Phenylalanine derivatives: Tyrosine L-dopa Dopa NE Epi ```
45
[Synthesis of non essential AA] glutamate
glutamine
46
[Synthesis of non essential AA] glutamate semialdehyde
1. Proline | 2. Arginine
47
{specialized products of amino acids] Coenzyme A needs
cysteine
48
{specialized products of amino acids] taurine needs
cysteine
49
{specialized products of amino acids] sphingosine
serine
50
S-adenosylmethionine supplies methyl groups to what reactions
1. Guanidoacetate to creatine 2. Phosphatidylethanolamine to phosphatidylcholine 3. NE to Epi 4. Acetylserotonin to melatonin 5. Polynucleotides to methylated polynucleotides
51
[Catecholamine Syntesis] Tyrosine to DOPA
Tyrosine hydroxylase
52
[Catecholamine Syntesis] dopa to DOPAMINE
DOPA decarboxylase
53
[Catecholamine Syntesis] what vitamin is needed to convert dopamine to NE
Vitamin C
54
[Catecholamine Syntesis] what mineral is needed to convert dopamine to NE
copper Tyrosinase needs copper
55
What is the excretory form of dopamine?
Homovanillic acid HVA
56
What is the excretory form of NE and Epi?
VMA
57
What enzymes degrade catecholamines
1. MAO | 2. COMT
58
What catecholamine product is increased in pheochromocytoma?
Vanillylmandelic Acid (VMA)
59
[Amino acid disorder] What enzyme deficiency is present in phenylketonuria
1. Phenylalanine hydroxylase | 2. Tetrahydrobiopterin
60
What amino acid becomes essential in phenylketonuria?
Tyrosine
61
What gives phenyketonuria its distinct odor?
Phenylpyruvate = musty odor
62
[Diagnosis] mental retardataion, dailure to walk or talk, seizure, fair skin, eczema, musty body ordor
phenylketonuria
63
[Amino acid disorder] What enzyme is deficient in alkaptonuria?
homogentisate oxidase
64
What amino acid is degraded by homogentisate oxidase
tyrosine
65
[Diagnosis] dark connective tissues with debilitating arthralgia, urine turns black on standing
Alkaptonuria
66
What is responsible for the blackening of the urine in patients with alkaptonuria?
Alkapton bodies Homogentisate is oxidized by polyphenyl oxidase to become bezoquinine acetate = blackening
67
[Diagnose] absence of pigment from hair, eyes, skin increased risk for cancer
Albinism, lacks tyrosinase
68
[Diagnose] cabbage like odor, accumulation of fumarulacetoacetate in liver, kidney and nervous system increased risk for liver CA
Tyrosinemia Type I Defect in fumaryacetoacetate hydrolase
69
[Diagnose] enzyme affected in tyrosinemia type II which affects the eyes, skin, mental development
tyrosine aminotransferase
70
[Diagnose] High plasma and urinary levels of homocysteine and methionine, low levels of cystein
Homocysteinuria
71
What is the most common deficiency in patients with homocystinuria?
cystathionine beta synthase
72
[Diagnose] Lens displace downward, faulty bone development, osteoporosis mental retardation tendency to form thrombi, MI, stroke
homocysteinuria
73
What is the enzyme is needed to convert homocysteine to cystein?
Cystathionine beta synthase Coenzyme: pyridoxal phosphate
74
What enzyme is needed to convert homocysteine to methionine?
Methionine synthase Coenzyme: methylcobalamin
75
What amino acid transporters in the PCT are affected in patients with cystinuria?
1. Cystine 2. Ornithine 3. Lysine 4. Arginine
76
[Diagnose] Excess cystine in the urine, presence of cystine renal stones
cystinuria
77
What is the DOC for cystinuria?
Acetazolamide to alkalinize the urine
78
Amino acids that are converted to methymalonyl CoA from propionyl CoA
VITM
79
[Diagnose] Siezure, encephalopathy, stroke at age of 1 month to 1 year old hypotonia, lethargy, failure to thrive, hepatosplenomegaly, monilial infections
Methymalonic acidemia
80
The characteristic urine odor of MSUD is due to the?
alpha keto acids
81
What enzyme is deficient in patients with MSUD?
alpha ketoacid dehydrogenase complex
82
Histidase converts histidine to ____
urocanate
83
Waste nitrogen from skeletal AA catabolism is brought to the liver for incorporation into urea by what?
Alanine muscle = mAsel = Alanine

Biochemistry (28 decks)

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