Metabolic waste

Source: Wikipedia, the free encyclopedia.
This article is about unwanted substances expelled from living organisms. For similar terms with different meanings, see Waste (disambiguation).

Metabolic wastes or excrements are

metabolic pathways
which transforms some of them (primarily the oxygen compounds) into useful substances.

All the metabolic wastes are excreted in a form of

Malpighian tubules, kidneys), with the exception of CO2, which is excreted together with the water vapor throughout the lungs. The elimination of these compounds enables the chemical homeostasis
of the organism.

Nitrogen wastes

The nitrogen compounds through which excess nitrogen is eliminated from organisms are called nitrogenous wastes (/naɪˈtrɒdʒɪnəs/) or nitrogen wastes. They are ammonia, urea, uric acid, and creatinine. All of these substances are produced from protein metabolism. In many animals, the urine is the main route of excretion for such wastes; in some, it is the feces.

Ammonotelism

Ammonotelism is the excretion of ammonia and ammonium ions. Ammonia (NH3) forms with the oxidation of amino groups.(-NH2), which are removed from the proteins when they convert into carbohydrates. It is a very toxic substance to tissues and extremely soluble in water. Only one nitrogen atom is removed with it. A lot of water is needed for the excretion of ammonia, about 0.5 L of water is needed per 1 g of nitrogen to maintain ammonia levels in the excretory fluid below the level in body fluids to prevent toxicity.[

poriferans, echinoderms, and other aquatic invertebrates.[2]

Ureotelism

Further information: Urea § Physiology, and Urea cycle

The excretion of urea is called ureotelism. Land animals, mainly amphibians and mammals, convert ammonia into urea, a process which occurs in the liver and kidney. These animals are called ureotelic.[2] Urea is a less toxic compound than ammonia; two nitrogen atoms are eliminated through it and less water is needed for its excretion. It requires 0.05 L of water to excrete 1 g of nitrogen, approximately only 10% of that required in ammonotelic organisms.[citation needed]

Uricotelism

Uricotelism is the excretion of excess nitrogen in the form of

kidney stones and gout
, but also functioning as a blood antioxidant.

Water and gases

These compounds form during the catabolism of carbohydrates and lipids in condensation reactions, and in some other metabolic reactions of the amino acids. Oxygen is produced by plants and some bacteria in photosynthesis, while CO2 is a waste product of all animals and plants. Nitrogen gases are produced by denitrifying bacteria and as a waste product, and bacteria for decaying yield ammonia, as do most invertebrates and vertebrates. Water is the only liquid waste from animals and photosynthesizing plants.[4]

Solids

iron bacteria by using soluble forms. In plants, resins, fats, waxes, and complex organic chemicals are exuded from plants, e.g., the latex from rubber trees and milkweeds. Solid waste products may be manufactured as organic pigments derived from breakdown of pigments like hemoglobin, and inorganic salts like carbonates, bicarbonates, and phosphate, whether in ionic or in molecular form, are excreted as solids.[4]

Animals dispose of solid waste as feces.

See also

References

  1. ^ Chris M. Wood; R.S. Munger; D.P. Toews (1989). "Ammonia, urea, and H+ distribution and the evolution of ureotelism in amphibians" (PDF). Journal of Experimental Biology. 144: 215–233.
  2. ^
    ISBN 9788120341074
    .
  3. ISBN 978-93-86237-57-6
    .
  4. ^ a b "excretion." Encyclopædia Britannica. Encyclopædia Britannica Ultimate Reference Suite. Chicago: Encyclopædia Britannica, 2010.
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