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Nitrogenous Waste

Biology (Year 12) - Osmoregulation

Ben Whitten

What are nitrogenous wastes? Nitrogenous wastes are the nitrogen-containing metabolic waste products of the breakdown of proteins and nucleic acids, both biomacromolecules which contain nitrogen. Excretion is the removal of nitrogenous wastes. in mammals, the nitrogenous waste urea is removed as part of the urine. The elimination of nitrogenous wastes is essential, and there are 3 main nitrogenous wastes with varying levels of toxicity and solubility.

  • Ammonia is the most toxic, and the most soluble in water

  • Urea is moderately toxic, and moderately soluble in water

  • Uric acid is the least toxic, and the most insoluble in water

A build-up of ammonia in cells can affect their pH, making them more basic (increasing pH levels), which can denature enzymes and reduce metabolic activity as their function has been compromised. Various organisms have different ways of coping with this waste product. Some animals excrete ammonia directly, while many others expend energy to convert ammonia to a less toxic form, urea or uric acid, prior to excretion.

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