Nitrogenous Wastes Are Produced By

41.6: Nitrogenous Wastes - Nitrogenous Waste in Birds and Reptiles- Uric Acid

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Learning Objectives

Compare the major byproduct of ammonia metabolism in mammals to that of birds and reptiles

Of the iv major macromolecules in biological systems, both proteins and nucleic acids contain nitrogen. During the catabolism, or breakup, of nitrogen-containing macromolecules, carbon, hydrogen, and oxygen are extracted and stored in the class of carbohydrates and fats. Excess nitrogen is excreted from the body. Nitrogenous wastes tend to form toxic ammonia, which raises the pH of body fluids. The germination of ammonia itself requires energy in the class of ATP and large quantities of water to dilute it out of a biological system.

While aquatic animals tin can easily excrete ammonia into their watery surroundings, terrestrial animals have evolved special mechanisms to eliminate the toxic ammonia from their systems. The animals must detoxify ammonia by converting it into a relatively-nontoxic form such as urea or uric acrid.

Effigy \(\PageIndex{1}\): Nitrogen excretion: Nitrogenous waste is excreted in different forms by different species. These include (a) ammonia, (b) urea, and (c) uric acid.

Birds, reptiles, and near terrestrial arthropods, such as insects, are called uricothelic organisms because they convert toxic ammonia to uric acid or the closely-related compound guanine (guano), rather than urea. In dissimilarity, mammals (including humans) produce urea from ammonia; however, they also form some uric acrid during the breakup of nucleic acids. In this case, uric acid is excreted in urine instead of in carrion, as is washed in birds and reptiles.

Uric acid is a compound similar to purines found in nucleic acids. Information technology is water insoluble and tends to form a white paste or powder. The production of uric acid involves a circuitous metabolic pathway that is energetically costly in comparing to processing of other nitrogenous wastes such as urea (from the urea cycle) or ammonia; however, it has the advantages of reducing water loss and, hence, reducing the need for water.

Uric acid is also less toxic than ammonia or urea. Information technology contains four nitrogen atoms; just a small corporeality of h2o is needed for its excretion. Out of solute, it precipitates and forms crystals. The enzyme xanthine oxidase makes uric acid from xanthine and hypoxanthine, which in turn are produced from other purines. Xanthine oxidase is a large enzyme whose active site consists of the metal, molybdenum, spring to sulfur and oxygen. Uric acrid is released in hypoxic conditions.

Central Points

Nitrogenous wastes in the trunk tend to form toxic ammonia, which must be excreted.
Mammals such as humans excrete urea, while birds, reptiles, and some terrestrial invertebrates produce uric acid as waste.
Uricothelic organisms tend to excrete uric acid waste product in the form of a white paste or pulverization.
Conversion of ammonia into uric acid is more than energy intensive than the conversion of ammonia into urea.
Producing uric acid instead of urea is advantageous considering information technology is less toxic and reduces h2o loss and the subsequent need for h2o.

Key Terms

urea: a water-soluble organic compound, CO(NH2)ii, formed by the metabolism of proteins and excreted in the urine
guano: the excrement of seabirds, cave-dwelling bats, pinnipeds, or birds more generally
purine: any of a class of organic heterocyclic base containing fused pyrimidine and imidazole rings; they are components of nucleic acids
xanthine: a precursor of uric acid found in many organs of the body
hypoxanthine: an intermediate in the biosynthesis of uric acid
uric acid: a bicyclic heterocyclic phenolic compound, formed in the body past the metabolism of protein and excreted in the urine

Contributions and Attributions

OpenStax Higher, Biology. October 17, 2013. Provided by: OpenStax CNX. Located at: http://cnx.org/content/m44811/latest...ol11448/latest . License: CC BY: Attribution
Urea. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Urea . License: CC BY-SA: Attribution-ShareAlike
OpenStax College, Biology. December ii, 2013. Provided by: OpenStax CNX. Located at: http://cnx.org/content/m44811/latest...ol11448/latest . License: CC By: Attribution
Boundless. Provided by: Dizzying Learning. Located at: www.boundless.com//biological science/de...tion/ureotelic . License: CC By-SA: Attribution-ShareAlike
ornithine. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/ornithine . License: CC BY-SA: Attribution-ShareAlike
urea. Provided past: Wiktionary. Located at: en.wiktionary.org/wiki/urea . License: CC By-SA: Attribution-ShareAlike
OpenStax College, Nitrogenous Wastes. October 17, 2013. Provided past: OpenStax CNX. Located at: http://cnx.org/content/m44811/latest...e_41_04_01.jpg . License: CC Past: Attribution
OpenStax Higher, Biological science. October 17, 2013. Provided by: OpenStax CNX. Located at: http://cnx.org/content/m44811/latest...ol11448/latest . License: CC Past: Attribution
Uric acid. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Uric_acid . License: CC Past-SA: Attribution-ShareAlike
Metabolic waste. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/Metabolic_waste . License: CC BY-SA: Attribution-ShareAlike
OpenStax Higher, Biological science. December 2, 2013. Provided by: OpenStax CNX. Located at: http://cnx.org/content/m44811/latest...ol11448/latest . License: CC BY: Attribution
purine. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/purine . License: CC Past-SA: Attribution-ShareAlike
xanthine. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/xanthine . License: CC BY-SA: Attribution-ShareAlike
guano. Provided by: Wikipedia. Located at: en.Wikipedia.org/wiki/guano . License: CC BY-SA: Attribution-ShareAlike
hypoxanthine. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/hypoxanthine . License: CC By-SA: Attribution-ShareAlike
urea. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/urea . License: CC BY-SA: Attribution-ShareAlike
uric acid. Provided by: Wiktionary. Located at: en.wiktionary.org/wiki/uric_acid . License: CC BY-SA: Attribution-ShareAlike
OpenStax College, Nitrogenous Wastes. October 17, 2013. Provided by: OpenStax CNX. Located at: http://cnx.org/content/m44811/latest...e_41_04_01.jpg . License: CC Past: Attribution
OpenStax College, Nitrogenous Wastes. October 17, 2013. Provided by: OpenStax CNX. Located at: http://cnx.org/content/m44811/latest...1_04_02abc.jpg . License: CC Past: Attribution

Nitrogenous Wastes Are Produced By,

Source: https://bio.libretexts.org/Bookshelves/Introductory_and_General_Biology/Book:_General_Biology_%28Boundless%29/41:_Osmotic_Regulation_and_the_Excretory_System/41.06:_Nitrogenous_Wastes_-_Nitrogenous_Waste_in_Birds_and_Reptiles-_Uric_Acid

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