Nitrogen waste metabolism Flashcards
What are the 3 possible forms of nitrogenous waste?
Ammonia, urea, uric acid
What is the problem with using ammonia as your form of nitrogenous waste?
Its super toxic and requires a ton of water to get rid of
What is the problem with using uric acid as your form of nitrogenous waste?
Metabolically expensive
What are the two insoluble of uric acid breakdown?
Allantoin and allantoic acid
How is ammonia transported around?
As ammonium, NH4+
What form of nitrogenous waste do ammonotelic animals use?
Ammonia, NH3
What type of animals are ammonotelic?
Aquatic animals and humidic animals. Seen in fish, aquatic molluscs, simple invertebrates, larval amphibians
Why are pill bugs an exception to how ammonotelic animals usually process NH3?
They are able to exhale NH3 as a gas
How do ammonotelic animals get ammonium across cell membranes?
NH4+/H+ antiporter
What form of nitrogenous waste do uricotelic animals use?
Uric acid
Why is uric acid so metabolically expensive?
Requires a lot of ATP to get rid of
How is uric acid excreted?
As a semi-solid paste along with its related derivatives (guanine and allantoin)
Why is uric acid not toxic?
It isn’t very soluble, so it can’t do very much
Which animals use uriotelic nitrogen metabolism?
Terrestrial molluscs and arthropods, birds, reptiles
What nitrogenous waste product do ureotellic animals use?
Urea
What animals use ureotelic nitrogen metabolism?
All mammals, some larval teleosts, some lung fish, elasmobranchs
How toxic is urea?
Not as toxic as NH3, but an animal can still only tolerate so much
What is required to get rid of urea?
Lots of different enzymes and lots of ATP
How is urea transported across membranes in elasmobranchs?
Their gills and kidneys have an Na+/urea antiporter to be able to reuptake urea to maintain the hyperosmotic and hypoionic blood
Does making NH3 use ATP?
No, but it requires energy to get rid of
