In cells, this energy comes from the oxidation of fuel molecules, like carbons and fats.
Green plants use light as their primary energy source.
Reactions that require energy get their energy by splitting ATP into either ADP or AMP and inorganic phosphate. Chapter 9 discusses the reaction systems which synthesize ATP by harnessing the energy released from the oxidation of organic molecules. Oxidative phosphorylation Cellular oxidations are the immediate source of electrons at elevated energy levels. The primary fuel substances used in most cells are either carbohydrates or lipids. The electron transport system consists of a series of carrier molecules which are embedded in a membrane.