An ion is an atom that has gained or lost one or more electrons, resulting in a net positive or negative charge. Ions are created when atoms gain or lose electrons through chemical reactions. When an atom loses an electron, it becomes positively charged; when it gains an electron, it becomes negatively charged. The number of protons in the nucleus determines the element, while the number of electrons orbiting the nucleus determines the charge of the ion. When an electron is removed, the resulting positively-charged ion is called a cation; when an electron is added, the resulting negatively-charged ion is called an anion.
Ions play a significant role in many biochemical processes and are important for cell function. For example, ions are responsible for nerve impulses and muscle contraction. In addition, ions help to regulate fluid balance within cells and blood pH levels. Without ions, these processes would not be possible.
Ions can be found in both organic and inorganic compounds. Inorganic compounds are typically minerals that do not contain carbon-hydrogen bonds (elements other than hydrogen and carbon). Organic compounds are molecules that contain carbon-hydrogen bonds (compounds containing only hydrogen and carbon). Examples of common organic ions include amino acids (the building blocks of proteins) and nucleotides (the building blocks of DNA/RNA).