Nitrogenous waste

Out of interest. Why doesn't all life excrete Uric Acid if it is less toxic and you dont need to lose water in getting rid of it. Is the process of its production more complex?

Surely urea is inefficient if water is lost in its excretion. Allright with fish, there is water avaiblable anyway, so thats not a problem.

Reply 1

Golden Maverick

4

Fluent in Lies

Out of interest. Why doesn't all life excrete Uric Acid if it is less toxic and you dont need to lose water in getting rid of it. Is the process of its production more complex?

Surely urea is inefficient if water is lost in its excretion. Allright with fish, there is water avaiblable anyway, so thats not a problem.

Urea is a result of protein metabolism, and uric acid of nucleic acid metabolism.

If the concentration of uric acid gets too high in our blood, you get gout, where the acid crystallises in your joints. Also they help give you kidney stones.

I think animals that do excrete uric acid have an enzyme to stop this from happening, by making it soluble but I think this has been switched off in humans. Why, I don't know.

Reply 2

Seth

8

Fluent in Lies

Surely urea is inefficient if water is lost in its excretion.

It's a good point, but the conversion of ammonia into urea already saves some water because ammonia itself would require much more water for its removal due to its toxicity.

Reply 3

tangsiuje

2

My bio teacher said we should think about it as a trade-off between a variety of factors, such as toxicity, water solubility, need of water conservation, energy required for production, etc.

Uric acid might be less toxic than urea, but why would we waste energy in producing it if water is available for excretion?! For birds, low body weight and water conservation is top priority (enabling long-distance flights) --> there is a use of producing uric acid.

Thus, mammals secreting urea is not necessarily inefficient.

Reply 4

OldakQuill

4

Nitrogenous waste

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