Nature of Light from the Perspective of a Biologist What Is a Photon?

Authored by: Randy Wayne

Handbook of Photosynthesis

Print publication date:  March  2016
Online publication date:  April  2016

Print ISBN: 9781482230734
eBook ISBN: 9781482230758
Adobe ISBN:


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Isaac Newton (1730) asked, “Are not gross Bodies and Light convertible into one another, and may not Bodies receive much of their Activity from the Particles of Light which enter their Composition?” Photosynthesis is the process by which plants and other autotrophic organisms transform the rapidly flowing radiant energy of sunlight into sTable and stored chemical energy (Herschel 1833; Mayer 1845; Boltzmann 1886; Franck and Wood 1936; Franck and Herzfeld 1941; Oppenheimer 1941; Arnold and Oppenheimer 1950; Calvin 1959; Arnon 1961; Clayton 1971; Kamen 1985; Laible et al. 1994; Campbell and Norman 1998; Jagendorf 1998; Fuller 1999; Govindjee 2000; Feher 2002; Monteith and Unsworth 2008; Nobel 2009; Wayne 2009b). Photosynthesis, the basic process that feeds the world, begins when the pigments in the antenna complex capture the sunlight and transfer the energy to the pair of chlorophyll molecules that make up the reaction center of a photosystem. The chlorophyll molecules in the reaction center undergo a photochemical charge separation that initiates a sequence of oxidation–reduction reactions that generate an electrochemical potential gradient across the photosynthetic membrane. These electrochemical events facilitate the fixation of carbon dioxide and the evolution of oxygen. These life-sustaining energy conversion processes are initiated by the absorption of a particle of light now known as a photon; but what is a photon?

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