Lipid metabolism and urea cycle Flashcards Preview

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Flashcards in Lipid metabolism and urea cycle Deck (36):
1

conjugation

addition of glucuronic acid -> bilirubin diglucuronide
catalyzed by UDPGT

2

urobilin

yellow
in urine

3

sterobilin

brown in feces

4

catabolism of hemoglobin

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

5

bacterial beta glucuronidases

hydrolyze conjugated bilirubin back to unconjugated

6

urobilinogens

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

7

jaundice

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

8

hemolytic anemia

excess hemolysis
large increase in unconjugated bilirubin
increase in conjugated bilirubin

9

hepatitis

large increase in both conjugated and unconjugated

10

biliary stone

large increase in conjugated
small increase in unconjugated

11

pre-hepatic jaundice

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

12

intra-hepatic jaundice

can be caused by:
-gilberts syndrome
-crigler-najjar type I syndrome
-dubin-johnson sundrome
-hepatitis

13

gilberts syndrome

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

14

crigler-najjar type I syndrome

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

15

dubin-johnson syndrome

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

16

hepatitis

increased both
total 5-10 mg/dL

17

post hepatic jaundice

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

18

high conjugated

dubin-johnson
rotor
post-hepatic

19

high unconjugated

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

20

ciglner-najjar II

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

21

rotors syndrome

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

22

amino acid oxidation

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

nitrogen elimination

transamination or aminotransferase rxns
release of N from glutamate and its conversion to urea by urea cycle in liver

24

enzymatic transamination

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

glutamate dehydrogenase

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

26

glutamine synthetase

uses NH3 + ATP to convert glutamate to glutamine

27

step 1 urea cycle

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

28

step 2 urea cycle

citrulline converted to argininosuccinate
via argininsuccinate synthetase

29

step 3 urea cycle

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

30

step 4 urea cycle

arginine converted to urea and ornithine via arginase

31

urea cycle

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

urea cycle enzymes in mito

carbamoyal phosphate synthetase
ornithine transcarbamylase

33

urea cycle enzymes in cytosol

argino-succinate synthase
agrino-succinase
arginase

34

PKU

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

35

PAH

metabolizes phenylalanine to tyrosine and epiephrine
w/o PAH phenlyalanine -> phenylpyruvate

36

released w/liver damage and levels elevated

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