3 Main Nitrogenous Wastes (Excretion)
•1.  Ammonia
ØHighly toxic
ØHighly water soluble
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•2. Urea
ØLess toxic (100,000 less toxic than ammonia)
ØExcretion requires 10 times less water
ØEnergy often required (4 ATP per molecule)
ØConcentration up to 25 times that of  plasma
Ø
•3. Uric Acid
ØNon toxic
ØExcretion requires 50 times less water
ØEnergy intensive (8 ATP per molecule)
ØConcentration up to 3,000 times that of  plasma
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