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GI > Lipid metabolism and urea cycle > Flashcards

Lipid metabolism and urea cycle Flashcards

1
Q

conjugation

A

addition of glucuronic acid -> bilirubin diglucuronide

catalyzed by UDPGT

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2
Q

urobilin

A

yellow

in urine

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3
Q

sterobilin

A

brown in feces

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4
Q

catabolism of hemoglobin

A

heme -> biliverdin via heme oxygenase uses O2 produces CO2
biliverdin -> bilirubin (insoluble) via biliverdin reductase needed NADPH
conjugated in liver

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5
Q

bacterial beta glucuronidases

A

hydrolyze conjugated bilirubin back to unconjugated

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6
Q

urobilinogens

A

stercobilinogen -> stercobilin
mesobilinogen -> mesobilin
urobiliogen -> urobilin
about 20% reabsorbed into entero-hepatic ciculation

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7
Q

jaundice

A

bilirubin exceeds 2-3mg/dL
infants get kernicterus when exceeds 15-20mg/dL
can lead to brain damage

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8
Q

hemolytic anemia

A

excess hemolysis
large increase in unconjugated bilirubin
increase in conjugated bilirubin

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9
Q

hepatitis

A

large increase in both conjugated and unconjugated

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10
Q

biliary stone

A

large increase in conjugated

small increase in unconjugated

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11
Q

pre-hepatic jaundice

A 
aka hemolytic jaundice
excessive bilirubin presented to licer
increased total 
large increase in unconjugated
negative urine bilirubin
urinary urobilinogen high
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12
Q

intra-hepatic jaundice

A

can be caused by:

  • gilberts syndrome
  • crigler-najjar type I syndrome
  • dubin-johnson sundrome
  • hepatitis
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13
Q

gilberts syndrome

A 
enzyme mutation: UDP-glucuronyltransferase gene 
impaired hepatocellular uptake
total <3mg/dL, mostly unconjugated
increased urinary urobilinogen
mild jaundice
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14
Q

crigler-najjar type I syndrome

A 
incomplete absence of UDP-glucuronyltransferase 
defective conjugation
serum unconjugated >25mg/dL
increased urninary urobilinogen
fatal w/in 1 yr w/o liver transplant
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15
Q

dubin-johnson syndrome

A

defective secretion by hepatocytes
increased conjugated
liver has characteristic green-black color

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16
Q

hepatitis

A

increased both

total 5-10 mg/dL

17
Q

post hepatic jaundice

A

mechanical obstruction of flow
increased serum and urine conjugated bilirubin
decreased urobilin/stercobilin in stool (clay colored stool)
negative urinary urobilinogen

18
Q

high conjugated

A

dubin-johnson
rotor
post-hepatic

19
Q

high unconjugated

A

gilberts 25
ciglner-najjar II -5-20 mg/dL
lucey-driscoll- transiently around 5 mg/dL

20
Q

ciglner-najjar II

A

partial deficiency of UDP-glucuronyltransferase
unconjugated 5-20
responds to phenobarbital
normal life

21
Q

rotors syndrome

A

similar to dubin-johnson w/o pigementation of liver
high conjugated
moderate jaundice

22
Q

amino acid oxidation

A

leftover AA from normal protein turnover degraded
dietary AA that exceed bodys needs degraded
proteins in body are broken down to supply AA for catabolism when carbs are in short supply

23
Q

nitrogen elimination

A

transamination or aminotransferase rxns

release of N from glutamate and its conversion to urea by urea cycle in liver

24
Q

enzymatic transamination

A

all aminotransferases rely on pyridoxal phosphate cofactor
typically alpha-ketoglutarate accepts amino groups
L-glutamine acts as temporary storage of N
L-glutamine can donate the amino groip when needed for amino acid biosynthesis

25
Q

glutamate dehydrogenase

A

uses NADH to combine alpha-ketoglutarate and amino group to form glutamate

26
Q

glutamine synthetase

A

uses NH3 + ATP to convert glutamate to glutamine

27
Q

step 1 urea cycle

A

carbamoyl phosphate + ornithine -> citrulline
via ornithine transcarbamoylase
in matrix, passes into cytosol

28
Q

step 2 urea cycle

A

citrulline converted to argininosuccinate

via argininsuccinate synthetase

29
Q

step 3 urea cycle

A

arginocuccinate cleaved -> fumarate and arginine via argininosuccinase
these enter TCA cyle

30
Q

step 4 urea cycle

A

arginine converted to urea and ornithine via arginase

31
Q

urea cycle

A

primarily in liver, some in kidney
L-glutamie can be used to synthesize new AA or it can dispose of excess N as ammonia
nitrogen added to urea cycle via carbamoyl phosphate and aspartate

32
Q

urea cycle enzymes in mito

A

carbamoyal phosphate synthetase

ornithine transcarbamylase

33
Q

urea cycle enzymes in cytosol

A

argino-succinate synthase
agrino-succinase
arginase

34
Q

PKU

A

autosomal recessive
deficiency in PAH
increase in phenylalanine and phenylpyruvate, both toxic to CNS

35
Q

PAH

A

metabolizes phenylalanine to tyrosine and epiephrine

w/o PAH phenlyalanine -> phenylpyruvate

36
Q

released w/liver damage and levels elevated

A

ALT (alanine transaminase) , AST (aspartate transaminase) , ALP (alkaline phosphate), GGT (gamma-glutamyltransferase), LDH (L-lactated dehydrogenase)

GI (14 decks)

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