The human body is composed of various chemical elements. These elements combine to form the molecules that build cells, tissues, and organs, enabling all life processes. Understanding this elemental composition helps to reveal the foundational chemistry that underpins human biology.
The Dominant Element
Carbon is a highly abundant element in the human body, accounting for approximately 18.5% of its total mass. This makes it the second most prevalent element by mass, after oxygen. Carbon’s unique chemical properties allow it to form the framework of virtually all organic molecules, found throughout the body’s structures.
Carbon’s Crucial Roles in the Body
Carbon’s ability to form stable covalent bonds with up to four other atoms, including itself, makes it a building block for complex biological molecules. This versatility allows carbon atoms to create diverse structures, such as chains and rings, which are the backbones of the four major types of organic macromolecules.
Carbohydrates, composed of carbon, hydrogen, and oxygen, serve as the body’s energy source. Glucose is used for cellular energy production, while larger carbohydrates like starch and glycogen store energy. Carbon atoms form the structural skeleton of these sugar molecules, allowing for their diverse forms.
Lipids, including fats, oils, and steroids, are made of carbon and hydrogen, with some oxygen. They are important for long-term energy storage, insulation, and forming cell membranes. Their hydrocarbon chains contribute to energy density and water insolubility, which is essential for membrane formation.
Proteins are polymers of amino acids, each containing a central carbon atom. Carbon forms the backbone of these long chains, known as polypeptides. The arrangement of carbon-containing amino acids dictates a protein’s three-dimensional shape, determining its diverse functions as enzymes, structural components, or transport molecules.
Nucleic acids, DNA and RNA, store and transmit genetic information. Their nucleotides contain a five-carbon sugar (deoxyribose in DNA, ribose in RNA), a phosphate group, and a nitrogenous base. Carbon atoms are key to the sugar and nitrogenous base structures, forming the sugar-phosphate backbone that gives DNA its double helix shape and RNA its structure.
Beyond Carbon: Other Key Elements
While carbon is foundational, the human body relies on many other elements. Oxygen makes up the largest percentage by mass (around 65%), primarily from water. Hydrogen follows (about 9.5%), also from water and organic molecules. Nitrogen (roughly 3.2%) is a key component of proteins and nucleic acids.
Calcium (1.5%) is important for bone structure, muscle contraction, and nerve function. Phosphorus (0.6%) is crucial for energy transfer molecules like ATP and is part of bones and nucleic acids. Other elements like potassium, sulfur, sodium, chlorine, and magnesium play specific roles in maintaining physiological processes and overall health.