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Renal Midterm > Nitrogen Metabolism > Flashcards

Nitrogen Metabolism Flashcards

1
Q

first step of nitrogen removal and enzyme involved

A

oxidative deamination via glutamate dehydrogenase

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2
Q

key player in AA metabolism

A

glutamate

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3
Q

source of carbon skeletons for urea cycle generated from transamination reactions

A

aspartate

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4
Q

nitrogen sources for the urea cycle

A

Glu/Gln

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5
Q

inborn errors of AA resorption (2)

A

hartnup - nonpolar AA

Cystinuria - dibasic AA

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6
Q

AA are resorbed in which portion of the nephron

A

proximal convoluted tubule

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7
Q

cystinuria is characterized by defective ________ enzyme in what tissue

A

shared dibasic-cystine transporter in the proximal renal tubule and JEJUNAL MUCOSA

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8
Q

what picks up the slack for the shared dibasic-cystine transporter in the small intestines?

A

a peptide transporter

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9
Q

hartnup is characterized by a defective ________ enzyme in what tissue

A

neutral AA transporter in the proximal renal tubule and jejunal mucosa

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10
Q

most important AA that is ineffectively resorbed in the PCT in patients with hartnup is

A

tryptophan, precursor for neurotransmitters

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11
Q

dibasic AA

A 
COAL
Cystine 
Ornithine 
Argnine 
Lysine
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12
Q

neutral AA transporter deficiency

Ala, Ser, Thr, Val, Leu, Ile, Phe, Tyr, Trp, Gln, Asn

A

hartnup disease

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13
Q

Trp is the precursor for what molecules

A

serotonin
melatonin
niacin (which is a precursor for NAD) - note niacin deficiency

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14
Q

manifestations of Hartnup disease

A

failure to thrive, nystagmus, intermittent ataxia, tremor and photosensitivity
pellagra like dermatosis
attacks triggered by sunlight, drugs, physical stress

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15
Q

treatment for hartnup

A

nicotinic acid

niacin repletion and high protein diet, daily nicotinamide supplementation

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16
Q

nitroprusside test indicates

A

cystinuria

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17
Q

cystinuria can dissolve kidney stones by changing their diet to be more

A

alkalinic

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18
Q

phenylketonuria is caused by deficient

A 
Phenylalanine hydroxylase (PAH) 
most common IEM
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19
Q

PKU symptoms can be limited by

A

dietary limitation of Phe and supplementation of Tyr

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20
Q

secondary PKU is characterized by

A

Tetrahydrobiopterin deficiency
THB is a key coenzyme in phenylalanine hydroxylase
defect in synthesis/regeneration of B4

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21
Q

PKU babies must be treated before _____ of age
Dietary restrictions begin if blood Phe levels are greater than _____
some patients with milder forms can increase their metabolic control with supplementation with _______

A

2 weeks of age
6mg/dL
improved metabolic control when treated with THB

22
Q

Tetrahydriobiopterin is a cofactor for what enzyme

A

phenylalanine hydroxylase

23
Q

synthetic THB treats what IEM

A

secondary PKU

24
Q

tyrosinemias are characterized by

A

elevated blood levels of tyrosine

25
Q

deficient fumarylacetoacetate hydrolase results in what form of tyrosinemia and what does the enzyme do

A

Type I

converts tyrosime to fumarate

26
Q

type I tyrosinemia is characterized by deficient

A

fumarylacetoacetate hydrolase

27
Q

Type I tyrosinemia babies have a _____ like smell and excrete ______, which is toxic to liver and kidneys, interferes with the TCA cycle, causes renal tubule dysfunction and inhibits biosynthesis of heme

A

cabbage

secrete succinylacetone

28
Q

type II tyrosinemia is characterized by

A

defective tyrosine aminotransferase

results in photophobia/skin lesions

29
Q

type III tyrosinemia is characterized by

A

defective p-hydroxyphenylpyruvate oxidase and results in intermittent ataxia

30
Q

what type of tyrosinemia is most common and used to require a liver transplant?

A

type I
deficient fumarylacetoacetate hydrolase
buildup of succinylacetone

31
Q

defective homogentisate oxidase, an enzyme in tyrosine degradation pathway, results in black urine and bones is termed

A

alkaptonuria

32
Q

a buildup of homogentistic acid is due to what enzyme in alkaptonuria

A

homogentisate oxidase

33
Q

NH3 toxicity MoA

A

permeates membranes

pH imbalance, swelling of astrocytes in the brain –> cerebral edema/intracranial hypertension

34
Q

enzyme that catalyzes the oxidative deamination of glutamate to alpha-ketoglutarate

A

glutamate dehydrogenase

35
Q

ammonia depletes what NT

A

glutamate

36
Q

gout is a buildup of

A

uric acid in the blood and deposition of sodium urate crystals
primary hyperuricemia –> overproduction of uric acid
Secondary hyperuricemia –> underexcretion of uric acid

37
Q

diets rich in ________ along with what other foods/drinks trigger gout

A

purines

alcohol, meat, seafood

38
Q

treatments of gout

A

colchicine decreases the movement of granulocytes to the affected areas
use of allopurinol inhibits xanthine oxidase

39
Q

hyperammonemia is caused by defects in what enzymes

A

six enzymes of the urea cycle or 3 specific transporters

mitochondrial ornithine carriers, mitochondrial Asp/Glu carrier, dibasic AA transporter

40
Q

more severe cases of hyperammonemia are due to defects in what enzymes

A

3 specific transporters

mitochondrial ornithine carriers, mitochondrial Asp/Glu carrier, dibasic AA transporter

41
Q

ornithine transcarbamoylase deficiency results in what condition

A

hyperammonemia
defects cause excess carbamoyl phosphate which can spill out into cytoplasm
metabolized by pyrimidine synthesis pathway to orotic acid then accumulates/excreted in the urine (orotic aciduria) –> decreases BUN

42
Q

first step of de novo pyrimidine synthesis is mediated by what enzyme

A

carbamoyl phosphate synthetase II - cytosol

unique from mitochondrial isoform

43
Q

carbamoyl phosphate synthetase I

A

urea cycle
mitochondrial
NAG activated

44
Q

Carbomyl phosphate synthetase II

A

pyrimidine synthesis
cytosolic
PRPP activated

45
Q

Carbamoyl phosphate synthetase I is the rate limiting step for what process

A

urea cycle
deficiency == hyperammonemia
creates carbamoyl phosphate which is used added to ornithine to make citrulline (allows urea to exit the mitochondria)

46
Q

bilirubin is conjugated with

A

glucuronic acid

by UDP glucuronyl transferase

47
Q

unconjugated bilirubin is trasnported to the liver from the spleen using

A

albumin?

48
Q

heme is broken down to bilirubin in the

A

macrophage

49
Q

unconjugated bilirubin is water ______ while conjugated bilirubin is water _______

A

insoluble

soluble

50
Q

jaundice is common in newborns because

A

placenta handles removal of bilirubin, after birth babies liver must take over the job

Renal Midterm (7 decks)

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