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GI II > Liver metabolism- urea cycle > Flashcards

Liver metabolism- urea cycle Flashcards

(95 cards)

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1
Q

Where is bilirubin from

A

heme from broken down RBC

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2
Q

Where is heme taken up to be processed first

A

reticoendothelial cells of the spleen to form unconjugated bilirubin (lipid soluble) via heme oxygenate

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3
Q

How is unconjugated bilirubin transported to the liver

A

attached to albumin in the blood stream

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4
Q

What happens to unconjugated bilirubin in the liver

A

addition of glucuronic acid to produce conjugated bilirubin which is water soluble

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5
Q

What enzyme is responsible for the conjugation of bilirubin in the liver

A

UDPGT

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6
Q

Where is conjugated bilirubin converted into urobilinogen

A

intestines by intestinal bacteria

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7
Q

what forms of urobilinogen are excreted in stool

A

urobilin and stercobilin, oxidized forms

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8
Q

How does bile get recycled to liver

A

must be bound to albumin because not very water soluble

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9
Q

What does the van den berg test for

A

measures blood levels of conjugated and unconjugated bilirubin

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10
Q

Describe what the Intestine does to ocnjugated bilirubin

A

hydrolyzed back to unconj.
in distal ileum and colon the flora reduce unconjugated bilirubin to urobilinogen and then also oxidation makes the unconj.bilirubin brown colored

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11
Q

Urobilinogen is a collective term for what 3 tetrapyrroles

A

stercobilinogen
mesobilinogen
urobilinogen

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12
Q

where does the 20% of reabsorbed urobilinogen go

A

entero-hepatic circulation

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13
Q

how much bilirubin ends up in urine

A

2-5%

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14
Q

How much of total bilirubin is conjugated

A

<0.2 mg/dL

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15
Q

how do you calculate unconjugated bilirbuin

A

total - conjugated

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16
Q

What happens with elevations of serum bilirubin

A

deposition in sclera of eyes and tissue– icterus and jaundice

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17
Q

When does jaundice appear (what serum level)

A

2-3 mg/dL

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18
Q

What are the causes of jaundice

A

excessive production of bilirubin
reduced hepatocyte uptake
impaired bilirubin conjugation
impaired bile flow

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19
Q

At what serum level in infants will the result be kernicterus

A

15-20 mg/dL

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20
Q

What causes pre hepatic jaundice

A

hemolysis

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21
Q

what causes hepatic jaundice

A

viral hepatitis, drugs, alcohol, cirrhosis, recurrent cholestasis
enzyme mutations, defective secretion

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22
Q

What causes post hepatic jaundice

A

common duct stones, carcinomas of bile duct pancreas ampulla, biliary stricture
sclerosing cholangitis
pancreatic pseudocyst

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23
Q

In hemolytic anemia which bilirubin is elevated

A

unconjugated

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24
Q

In hepatitis what bilirubin is elvated

A

both unconj and conjugated

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25
with a biliary duct stone what bilirubin is elevated
conjugated
26
Describe pre-hepatic jaundice
excessive bilirubin presented to liver, too much causes hemolysis of RBC and results in increased serum unconjugated bilirubin Increase in urinary urobilinogen
27
Describe Intra-hepatic jaundice
abnormal hepatocyte function
28
What genetic disorders cause intra-hepatic jaundice
Gilbert's, Cirgler-Najjar type I, Dubin-Johnson
29
describe findings in someone with Gilberts
stress activated. total bilirubin is not elevated but increased unconjugated bill with increased urine urobilinogen
30
describe findings in someone with Crigler-Najjar syndrome I
unconj bili in serum is above 5 mg/dL and there is an increased urinary urobilinogen
31
describe findings in someone with dubin johnson syndrome
increased serum conjugated bill from defective secretion of hepatocyte
32
What are the findings in someone with hepatitis causing jaundice
increased direct and indirect bilirubin with total levels 5-10 mg/dL
33
What are the findings of someone with impaired excretion of bilirubin
increased serum AND urine conjugated bilirubin decreased urobilin and stercobilin (pale stool) no urinary urobilinogen
34
Malaria can cause what type of jaundice
pre-hepatic
35
In which type of jaundice is there and increase in fat in the stool
intra-hepatic
36
What liver function enzymes will be impaired in someone with an intrahepatic jaundice
SGOT and SGPT
37
What is kernicterus
brain encephalopathy referring to the yellow staining of basal ganglia caused by excessive jaundice
38
how does bilirubin cross blood brain barrier in a newborn
the barrier is not fully formed
39
What causes the prolonged jaundice in newborns
polycythemia | Rh incompatability with mom
40
What are inherited disorders of bilirubin metabolism
gilberts, crigler-najjar type I and II | lucey-driscoll, dubin-johnson, rotors syndrome
41
What genetic conditions can you suspect in someone with elevated conjugated bilirubin
Dubin-johnson and rotors
42
What is mutated in someone with Gilbert's syndrome
UDPGT- low activity
43
What is mutated in Crigler najjar syndrome type I
incomplete absence of UDPGT | high high levels of unconjugated bilirubin
44
What type of inheritance is Crigler najjar syndrome type I
autosomal recessive
45
What is the Tx for crigler najjar syndrome I
liver transplant within first year of life
46
What type of inheritance is crigler najjar type II
autosomal dominant
47
What mutation is in crigler najjar type II
partial deficiency of UDPGT
48
What is the Tx for crigler najjar syndrome type II
responds to phenobarbital and normal life can be expected
49
What type of inheritance is dubin johnson
autosomal recessive
50
Impairment of the excretion of various conjugated anions and bilirubin into bile reflects what in dubin johnson syndrome
underlying defect in cnalicular excretion
51
What does the liver look like in someone with dubin johnson
dark brown pigment in hepatocytes and kupffer cells
52
How do you rule out rotors from dubin johnson
does not have pigmented liver, non itching jaundice
53
What is alcohols mech of leading to jaundice
decreased excretion of bilirubin into bile. hyperbilirubinemia
54
What are the various sources for aa
body protein, de novo synthesis from carbon and Nitrogen, dietary aa
55
What can aa be turned into
body protein, urea and O2 and biosynthesis of N compounds like creatine, hormones, nucleotides etc
56
What 3 circumstances lead to aa oxidative catbolism
leftover aa from normal protein dietary aa that exceed need proteins in body that are broken down (starvation, DM)
57
What 2 key processes does the liver do in metabolic nitrogen elimination
transamination of aminotransferase reactions | release of nitrogen from glutamate and conversion into urea by the urea cycle
58
how does the liver assist in ammonia detoxification
urea cycle
59
which molecular group is removed from aa first before any breakdown
the amino group
60
all aminotransferases rely on what cofactor
the pyridoxal phosphate cofactor
61
which compound accepts the amino groups
alpha ketoglutarate
62
What aa is a temporary storage for nitrogen
L glutamine, will donate if amino group needed for biosynthesis
63
What is the role of glutamate dehydrogenase
aketoglutarate and NH4--> glutamate with help of NADH-->NAD+
64
What two enzymes are involved in non-hepatic removal of ammonia
glutamate dehydrogenase and glutamine synthetase
65
What two enzymes in the liver are involved with excreiton of N via urea production
aminotransferase and glutamate dehydrogenase
66
How is excess ammonia transported in tissues because is toxic
attaches to glutamine via glutamine synthetase | enters blood to liver where NH4 is liberated in mitochondria by glutaminase
67
How many steps are there in the urea cycle
4
68
Describe first step in urea cycle
carbamoyl phosphate combined with ornithine form citrulline so can pass into cytosol
69
describe the second step in urea cycle
citrulline is converted to arginino-succinate thorugh a citrullyl-AMP intermediate
70
describe the third step of the urea cycle
argininosuccinate is cleaved via argininosuccinase to yield fumarate and arginine which enters the citric acid cycle
71
describe the fourth step of the urea cycle
formation of urea- arginine is converted to urea and ornthinine via arginase
72
What is the link between the citric acid cycle and urea cycle
arginosuccinate can be converted to fumurate (which can then be converted to malate) and enters citric acid cycle
73
Where is the most common site of the urea cycle
liver and sometimes kidney
74
toxic ammonia is quickly recaptured by what
carbamoyl phosphate and passed into urea cycle
75
how is nitrogen added to urea cycle
carbamoyl phosphate and aspartate
76
what are the enzymes of urea cycle that are in the mitochondria
carbamoyl phosphate synthestase | ornithine trans carbamylase
77
What are the enzymes in the cytosol of urea cycle
arginino-succinate synthase arginino- succinase arginase
78
Complete loss of urea cycle enzymes cause what
death shortly after birth
79
deficiencies in urea cycle enzymes lead to what
hyperammonemia (elevated ammonia in blood) | also lead to build up of glutamine and glutamate which can cause brain swelling
80
How are urea cycle disorders Tx
restricting dietary protein intake to limit nitrogen | metabolic substrates given to increase biosynthesis of nitrogen containing compunds that are excreted
81
What do we Tx people with argininosuccinase deficiency
high doses of L arginine
82
What causes phenylketonuria
problem with phenlyalanine hydroxyls PAH which converts phenylalanine to tyrosine and epinephrine
83
What inheritance is phenylketonuria
autosomal recessive
84
What is the result of a defective PAH
increase phenylpyruvate which is harmful
85
people who do not stick to low phenylalanine diet with phenylketonuria develop what
AHDH
86
What common food source contatins high phenylalanine
Nutrasweet, artificial sweetener. has aspartame
87
What are common liver function tests
ALT, AST, ALP, albumin, bilirubin, GGT, LDH and PT
88
describe alanine transaminase (ALT)
enzyme in liver cells that metabolize protein low levels in blood released into blood when liver is damaged
89
describe aspartate transaminase (AST)
metabolizes alanine and is found in high [ ] in liver, if elvels increase further indicative of liver damage
90
describe alkaline phosphatase (ALP)
in liver and bile ducts as well as other tissues. | highger than normal levels indicate liver damage or disease
91
Low levels of albumin and total protein are indicative of what
liver damage because this shows how well liver is making proteins to fight infections and perform functions
92
What is the gamma-glutamyltransferase test for
measures amount of enzyme in blood. If elevated suggest liver or bile duct damage
93
L -lactate dehydrogenase test is for what
elevated levels may indicate liver damage, found in other tissues too
94
Why is the prothrombin time aliver function test
measures clotting time. Increased PT indicates liver damage since liver produces thrombin and fibrinogen
95
why does liver damage lead to increased plasma ammonia
blood is shunted away from liver--> ammonia catabolism is decreased

GI II (12 decks)

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