Elemental Ratios: CHNOPS

Life as we know it is primarily composed of the elements carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—collectively known as CHNOPS.

These elements form the foundation of biomolecules like proteins, nucleic acids, lipids, and carbohydrates. In biological systems, CHNOPS elements are enriched and maintained in relatively stable ratios, such as the well-known Redfield Ratio in marine ecosystems. While these elements can be found in abiotic materials, their relative abundances and co-occurrence in specific proportions may indicate biological processing and help differentiate between living and non-living sources.

Created at: 
2021-01-11
Updated at: 
2025-06-23
Curator: 
Graham Lau
Authors: 
Stan Gliniewicz , Graham Lau  
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Definition
HIGH
LOW

CHNOPS elements are universally used by life on Earth, making them a foundational biosignature for life as we know it.

Biological macromolecules (proteins, nucleic acids, lipids) are built almost entirely from CHNOPS elements. [General]

Environments
All
eCHNOPS form >95 % of biomass and are present in all known biopolymers.

 
Definition
HIGH
LOW

CHNOPS ratios like Redfield stoichiometry result from active biological regulation.

Marine plankton maintain a consistent C:N:P near 106:16:1. [Production]

Environments
All
eRedfield’s original data and modern global compilations support consistent ratios.

 
Definition
HIGH
LOW
Definition
HIGH
LOW