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BIOB34H3 (271)
Lecture

NITROGEN EXCRETION.docx

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Department
Biological Sciences
Course
BIOB34H3
Professor
Jason Brown
Semester
Summer

Description
SLIDE 295 of the waste nitrogen youre producing is coming from protein catabolism The other 5 comes from breakdown of purines and pyrimadinesSLIDE 3Animals cant store surplus amino acids If you want to store amino acids you want to build them into functional proteinsBreaking amino acids involves cutting the molecule and getting rid of the amine group The leftover carbon skeleton is used to build other molecules or oxidized as a source of energyAmino acid catabolism yields ammonia which is toxic for a variety of reasons Ammonia is toxic largely to the nervous system of animals because it inhibits metabolism in the nervous system so ATP levels fall in animals At the same time ammonia is good at displacing potassium from transporters This disrupts electric signalsAmino acid catabolism is not a simple process Only 3 amino acids in our body can have their amino acids directly removed One of them is glutamateThe vast majority of amino acids cant be deaminated directly They need to have their amine group transferred to some other molecule to generate one of these amino acids that can be deaminated directly like glutamateFor example an amino acid is transferred to an oxoglutarate to produce glutamate which can then be deaminated directlyWe liberate an ammonia molecule that we have to get rid of The main way many cells dump ammonia is that they take it and build another kind of amino acid So here we take a glutamate and use ATP to add an ammonia group to it to form Glutamine This is the main transport form of ammonia in the animal bodyGlutamine isnt toxic so we can transport it in the blood and transport it to the site where we can excrete it pull the ammonia off and excrete itSLIDE 4We can take cellular proteins and ingested proteins and hydrolyze them to liberate amino acidsWe cant store excess amino acids so what do we do with themSome marine invertebrates such as crayfish can retain amino acids in their circulatory fluid and use them to adjust to the salinity of the environment in which they live in
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