module 12 Flashcards
nitrogen fixation
carried out by cyanobacteria, converts N2 to ammonia
higher organisms get nitrogen in form of NH3, which is incorporated into several carbon skeletons
what can be formed from NH3
alpha keto glutarate. glutamate, aspartate, CO2, ATP
form glutamate, glutamine, and asparagine, reactions are reversible
protein turnover
allows for replacement of damaged proteins, rate of breakdown is important for controlling enzyme levels
important for nucleotides, non protein amino acids, and other nitrogen containing compounds
types of non protein amino acids
ornithine, citrulline, sarcosine
nitrogen excretion
most vertebrates excrete it as urea which is water soluble, uric acid and ammonia are also ways to excrete it
transamination -
transfer of amino group from one molecule to another, alpha keto acid generates an amino acid. They are pyridoxal phosphate and transaminase dependent.
oxidative deamination -
amine is removed from ammonia, catalyzed by glutamate dehydrogenase, NADH, NH4+ are generated
alpha ketoglutarate formed enters citric acid cycle, NADH goes into ETC or cellular respiration
where is glutamate dehydrogenase found
mitochondrial membrane
glutamine deamination -
one ammmonium freed by glutaminase to yield glutamate.
glutamine synthetase
found in liver, allows it to sequester ammonia as glutamine as urea biosynthesis becomes overwhelmed, allows liver to detoxify amines
glutamate dehydrogrenase -
passes extra nitrogen to urea cycle in liver.
glucose alanine shuttle -
transfers ammonia to liver for conversion to urea.
how do most tissues use glutamate
most tissues convert glutamate to glutamine using ammonia and atp. This glutamine is then moved into the liver
what happens to glutamine in the liver
glutaminase releases nitrogen from glutamine, regenerating glutamate and moving NH4 to urea cycle
glucose alanine shuttle muscle step 1
ammonium passed to alpha ketoglutarate, converting it to glutamate, which transaminates pyruvate to form alanine that moves into the liver.