Electron acceptor
An electron acceptor is a chemical species that receives electrons in a redox reaction, becoming reduced while another species is oxidized.
What an electron acceptor is
An electron acceptor is a substance that takes electrons from another substance during a redox reaction. By accepting electrons, it is reduced. The substance that gives up electrons is the electron donor and is oxidized.
Accepting electrons means being reduced
The wording can feel backward at first: the acceptor gains electrons but is said to be reduced. In redox chemistry, reduction means gain of electrons, while oxidation means loss of electrons. The two always happen together because electrons must go somewhere.
Oxidizing agents
An electron acceptor is often called an oxidizing agent because it causes another substance to be oxidized. Oxygen, nitrate, ferric iron, sulfate, and many metal ions can act as electron acceptors in the right chemical or biological setting.
Redox potential matters
Electron acceptors differ in how strongly they tend to gain electrons. Redox potential helps compare that tendency. A strong acceptor can pull electrons from a donor more readily, but real reactions still depend on concentration, pH, enzymes, catalysts, and the surrounding environment.
Respiration uses terminal acceptors
In cellular respiration, electrons move through carriers and eventually reach a terminal electron acceptor. In aerobic respiration, oxygen fills that role and forms water. In anaerobic respiration, some microbes use alternatives such as nitrate, sulfate, ferric iron, carbon dioxide, or other compounds.
Why microbes care
Different electron acceptors yield different amounts of usable energy. Microbial communities therefore change with redox conditions. When oxygen disappears from wetlands, sediments, or aquifers, microbes may shift toward nitrate reduction, iron reduction, sulfate reduction, methanogenesis, or related anaerobic pathways.
Not the same as a proton acceptor
An electron acceptor is different from a Bronsted-Lowry base, which accepts a proton. Some reactions involve both protons and electrons, especially in biology and water chemistry, but electron transfer and proton transfer are separate ideas.
Why it matters
Electron acceptors are a small idea with a wide reach. They help explain batteries, corrosion, combustion, photosynthesis, respiration, wastewater treatment, groundwater chemistry, nutrient cycling, and the energy strategies microbes use when oxygen is scarce.