ESS102H1 Lecture Notes - Nitrification, Lithotroph, Heterotroph
Document Summary
The capacity of living organisms to mediate oxidation-reduction reactions is surpassed only by the tremendous diversity of life on earth, particularly among microorganisms that inhabit virtually every conceivable environment where liquid water is found. Redox processes are essential in bioenergetics and intermediary metabolism, and intimately couple all biological entities physicochemically to their surroundings. This coupling further sustains a wide spectrum of vital and dynamic relationships that underpin intense biogeochemical cycling of redox sensitive elements such as carbon, oxygen, nitrogen, iron, and sulfur. In oxidation-reduction reactions, electrons are donated from the oxidation of reduced ions or molecules characterized by a low half-cell eh, to oxidants with a higher half-cell eh. Spontaneous chemical reactions (i. e. , d g < 0; keq > q) are, in thermodynamic terms, exergonic. This is especially true of oxidation reactions, and means that work is done as energy is released by the reaction and moves into the surrounding region.
