the urea cycle Flashcards
how many steps does it take to produce urea
5
where do the process that produce urea take place
mitochondrial matrix and cytosol of hepatocytes
what enters the cycle at step one
NH4+ (free ammonium)
what enters the cycle at step three
aspartate
step one occurs where
matrix of the mitochondria
step one consists of what
condensation of waste materials
HCO3- derived from CO2 produced in mitochondrial respiration
what increases the activity of step one
allosteric modulator, N-acetylglutamate
what allosterically activates step one and what is it used for
arginine, which is used to synthesis ornithine
where is step two
mitochondrial matrix
what happens during step two
carbamoyl phosphate donates carbamoyl group to ornithine to form citrulline
where is step three
cytosol
what happens during step three
a second amino group is introduced by condensation of citrulline and asparate via a citrullyl-AMP intermediate
produces argininosuccinate
what type of reactions are the first 3 reactions
condensation
where is step four
cytosol
where is step five
cytosol
what is hyperammonaemia
a result of impaired liver function
what accompanies hyperammonaemia
raised levels of glutamine in blood as brain attempts to export excess ammonia
treatment for hyperammonaemia
dialysis or benzoate therapy
what happens in a hypercatabolic states
negative nitrogen balance
skeleton muscle protein broken down to produce glucose
urea synthesis and secretion increased
liver energy requirement increased
what is a hypercatabolic state
metabolic shutdown
when is metabolic acidosis observed
hypercatabolic states and prolonged fasts
