Life Needs an Electron Flow

Just as electricity is the flow of electrons, so too is life the flow of electrons.

Chemistry is the study of the reactions between atoms and molecules, which are all driven by electron flow. Biochemistry is the study of the reactions between the atoms and molecules of life, which are also driven by electron flow. Should this electron flow cease, chemical reactions will also cease, and an organism will die.

Electrons Come From Electron Donors

Living organisms need a constant supply of energy to survive — to metabolise, grow, and reproduce. That energy flow begins with an electron donor, a substance which donates its electron to another substance, which in turn donates to another and so on, releasing energy and driving cellular reactions along the way.

All living organisms can be classified into two groups, based on their electron donors: lithotrophs and organotrophs.

Lithotroph

From the Ancient Greek λίθος, líthos, ‘stone’; and τροφή, trophḗ, ‘nourishment’: ‘nourishment from stone’.

Lithotrophs obtain electrons from inorganic (mineral) substances. All plants, and many bacteria and archaea, are lithotrophs.

Organotroph

From the combining word organo-, ‘organic’ ; and τροφή, trophḗ, ‘nourishment’: ‘nourishment from organic (materials)’.

Organotrophs obtain electrons from organic compounds such as carbohydrates (especially glucose), fats and proteins. All animals, fungi and protozoa, and many bacteria and archaea, are organotrophs.