oxidation

Loss of electrons from an atom, ion, or molecule. Always paired with reduction (gain of electrons) in redox reactions — one cannot occur without the other.

redox

• oxidation: loss of electrons, increase in oxidation state
• reduction: gain of electrons, decrease in oxidation state
• oxidizing agent: accepts electrons (is itself reduced)
• reducing agent: donates electrons (is itself oxidized)

biological oxidation

• cellular respiration: glucose is oxidized to CO2, oxygen is reduced to H2O, releasing ~36 ATP
• electron transport chain: sequential redox reactions in mitochondria, the final step of aerobic metabolism
• antioxidants: molecules that donate electrons to neutralize free radicals (reactive oxygen species)

chemical oxidation

• rusting: iron + oxygen + water → iron oxide (Fe2O3)
• combustion: rapid oxidation releasing heat and light
• bleaching: oxidizing agents (chlorine, hydrogen peroxide) break chromophores

electrochemistry

Batteries convert chemical energy to electrical energy via separated redox half-reactions. Electrolysis uses electrical energy to drive redox reactions in reverse.

connections

combustion is violent oxidation. fermentation avoids oxidation by operating anaerobically. photosynthesis reverses oxidation by reducing CO2 back to sugar using light energy.