CHOUD BSC 1-24 Flashcards
What is the major product of nitrogen metabolism
urea
What is the ornithine cycle
urea cycle
where is ammonia from
aa catabolism
intracellularly what sequesters ammonia,
glutamic acid to form glutamine
where is the urea cycle
in the liver, and some in kidney
what transports glutamate from muscles
alanine
What organ produces alot of ammonia
brain
how is ammonium released from glutamine
glutamine–>glutamate–>alphaketoglutarate. each step releases an ammonium
how do we measure blood ammonium
BUN, nitrogen levels
In which organelle does urea cycle start
mitchondria
deficiency in carbamoyl phosphatase 1 will lead to what
high levels ammonium in blood= bad
what forms citrulline and why
carbamoyl and ornithine form citrulline so can be shuttle out of mitochondria into cytosol of lvier
What are the 5 steps urea cycle
carbamoyl phosphate combine with ornithine to form citrulline
citrulline converted to arginino-succinate
argininosuccinate cleaved f=to fumurate and arginine
urea and ornthinite formed
formation urea
What combines carbamoyl phsophate and ornithine to make citrulline
ornithine transcarbamoylase
What can result from elevated NH4 in blood
hyperammonemia–>toxic in brain, cerebral edema, convulsions, coma and death
What is the role of glutaminase synthetase
combines nitrogen and glutamate to make glutamine
What is the role of glutaminase
deaminates glutamine to glutamate and NH3
What 5 enzymes are important in urea cycle
carbamoylphosphate synthetase I ornithine transcarbamylase argininosuccinate synthetase argininosuccinate lyase arginase
What is the pacemaker enzyme of urea cycle
carbamoyl phosphate synthase I to keep cycel running
activity of CPS I is dictated by what
rate of synthesis from aCoA and glutamate because increases Nacetyl glutamateNAG
Why does starvation increase CPS I activity
increased production of ammonia from increased protein digestion
What causes citrullinemia
deficiency of argininosuccinic acid synthase
all (but one) urea cycle disorders are autosomal recessive. which one is not
ornithine transcarbomylase deficiency is X linked dominant- mitochondria
infant is vomiting drowsy increased temp and HR, hepatomegaly, high glutamine and uracil
what does this suggest
hyperammonemia- impaired urea formation
Probably ornithinine transcarbamoylase because increased uracil (orotic acid)
transamination enzymes are fine because glutamine is being made
Tx for ornithine transcarbomoylase deficiency?
give less protein in diet
supplemental dietary arginine
PTT that does not get better with Vit K bilirubin in urine high liver enzymes hypocalcemia low BUN what does this suggest?
chronic hepatitis B- end stage liver disease
Vit K no response shows liver is unable to synthesize the PT protein cofactors II VII IX and X
hypocalcemia because no albumin
low BUN–>liver
ALT is higher than AST in what pahtology
acute hepatitis
hypoabluminemia and prolonged PTT are markers for what
severe liver disease since liver synthesizes the proteins
macrocytic anemia suggests what
folate deficiency or B12 deficiency
Extreme levels of plasma ammonium in an infant usually means what
OTC deficient– x linked
CPS I affected
infants with urea cycle disorders present how
normal initially and rapidly develop cerebral edema, lethargy, anorexia, hyperventilation etc.
normal urea level
20-40 mg/dL
high glutamine and orotic acid in urine as well as low BUN is what disorder
mitochondrial OTC
HArtnup disease patients don’t become deficient in aa because what
PepT1
