CHNOPS

"CHON" redirects here. For people named Chon, see Chon (name). For other uses, see Chon (disambiguation).

CHNOPS and CHON are mnemonic acronyms for the most common elements in living organisms. "CHON" stands for carbon, hydrogen, oxygen, and nitrogen, which together make up more than 95 percent of the mass of biological systems.^[1] "CHNOPS" adds phosphorus and sulfur.

Graphic representation of carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur

Description

Carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur are the six most important chemical elements whose covalent combinations make up most biological molecules on Earth.^[2] All of these elements are nonmetals.

Element	Mass in plants	Mass in animals	Biological uses
Carbon	12%	19%	Found in carbohydrates, lipids, nucleic acids, and proteins.
Hydrogen	10%	10%	Found in water, carbohydrates, lipids, nucleic acids, and proteins.
Nitrogen	1%	4%	Found in nucleic acids, proteins, some lipids (e.g. sphingolipids) and some polysaccharides (e.g. chitin)
Oxygen	77%	63%	Found in water, carbohydrates, lipids, nucleic acids, and proteins.
Phosphorus	<1%	<1%	Found in lipids, nucleic acids and proteins.
Sulfur	<1%	<1%	Found in proteins and some polysaccharides.

In animals in general, the four elements—C, H, N, and O—compose about 96% of the weight, and major minerals (macrominerals) and minor minerals (also called trace elements) compose the remainder.^[1]

Sulfur is contained in the amino acids cysteine and methionine.^[3] Phosphorus is contained in phospholipids, a class of lipids that are a major component of all cell membranes, as they can form lipid bilayers, which keep ions, proteins, and other molecules where they are needed for cell function, and prevent them from diffusing into areas where they should not be. Phosphate groups are also an essential component of the backbone of nucleic acids (general name for DNA & RNA) and are required to form ATP – the main molecule used as energy powering the cell in all living creatures.^[4]

Carbonaceous asteroids are rich in CHON elements.^[5] These asteroids are the most common type and frequently collide with Earth as meteorites. Such collisions were especially common early in Earth's history, and these impactors may have been crucial in the formation of the planet's oceans.^[6]

The simplest compounds to contain all of the CHON elements are isomers fulminic acid (HCNO), isofulminic acid (HONC), cyanic acid (HOCN) and isocyanic acid (HNCO), having one of each atom.^[7]

See also

• Abundance of the chemical elements
• Biochemistry
• Bioinorganic chemistry
• Carbon-based life
• Micronutrient – Essential elements required by organisms