Life on Earth depends on a specific collection of chemical elements. An “essential element” is one an organism needs for normal growth, development, and reproduction that it cannot produce itself. These elements must be obtained from the environment.
The Fundamental Six
Six elements are the core building blocks of all living organisms: carbon (C), hydrogen (H), oxygen (O), nitrogen (N), phosphorus (P), and sulfur (S). These are often referred to as the “fundamental six” because they constitute the vast majority of an organism’s mass and are the primary components of organic molecules. Oxygen, carbon, hydrogen, and nitrogen alone make up about 99% of the atoms in the human body.
Carbon acts as the backbone of all organic molecules, forming stable bonds that create complex structures like proteins, carbohydrates, lipids, and nucleic acids. Hydrogen and oxygen are abundant in water, which is essential for life, and participate in energy transfer and the structural integrity of biomolecules. Nitrogen is a key component of amino acids, which build proteins, and nucleic acids like DNA and RNA. Phosphorus is fundamental for energy transfer, notably in adenosine triphosphate (ATP), and forms part of the backbone of DNA and RNA. Sulfur plays a role in the three-dimensional structure of proteins and various metabolic processes.
Additional Macro-elements for Life
Beyond the fundamental six, other elements are required in relatively large quantities, known as macro-elements. These include calcium (Ca), potassium (K), sodium (Na), magnesium (Mg), and chlorine (Cl). While less abundant, their functions are important for various physiological processes.
Calcium is known for its role in forming bones and teeth, and it also participates in muscle contraction, nerve signaling, and blood clotting. Potassium, the main electrolyte inside cells, is important for muscle function, nerve impulses, and heart rhythm. Sodium, a primary extracellular electrolyte, works with potassium to regulate fluid balance, nerve function, and muscle contraction. Magnesium acts as a cofactor for numerous enzymes, contributing to energy production and muscle relaxation. Chlorine aids in fluid balance and is involved in stomach acid production, which supports digestion.
Trace Elements
Organisms depend on trace elements, needed in very small amounts but essential for life. These elements often function as catalysts in enzyme systems or as components of larger biological molecules. Deficiencies or excesses can significantly impact an organism’s health.
Key Trace Elements
- Iron (Fe): Important for oxygen transport in blood (as hemoglobin component) and energy metabolism.
- Zinc (Zn): A constituent of over 200 enzymes, involved in nucleic acid metabolism, cell replication, tissue repair, and immune function.
- Copper (Cu): Involved in energy production, immune function, and bone health.
- Iodine (I): Necessary for thyroid hormone production, which regulates metabolism.
- Selenium (Se): Incorporated into enzymes that protect from oxidative damage and support immune function.
- Manganese (Mn): Important for bone formation and metabolism.
- Molybdenum (Mo): Activates enzymes.
- Chromium (Cr): Involved in insulin metabolism.
How Organisms Obtain Essential Elements
Living organisms acquire essential elements from their environment. Animals primarily obtain them through their diet, consuming food and water. Plants absorb most essential elements from the soil through their root systems. Carbon, however, is primarily taken up from the atmosphere as carbon dioxide. The continuous cycling of these elements through ecosystems, known as biogeochemical cycles, ensures their availability. The presence and concentration of these elements in the environment directly influence the health, growth, and distribution of life forms.