Chapter 20. Photosynthesis

SGARIGLIA, M. A.; SOBERÓN, J. R.; SAMPIETRO, D. A.; QUIROGA, E. N.; VATTUONE, M. A.

Plant biochemistry

Studium Press LLC

Lugar: Houston, Texas, USA; Año: 2009; p. 487 - 532

Photosynthesis is one of the most important biological phenomena on earth. The conversion of sunlight by photosynthetic organisms supplies most of the energy required to develop and sustain life on the planet. Photosynthetic organisms use solar energy to synthesize carbon compounds that cannot be formed without an energy input. More specifically, light energy drives the synthesis of carbohydrates from carbon dioxide and water with the generation of oxygen. Energy stored in these molecules can be used for plant metabolic processes and as energy source for all life forms. In plants, photosynthesis occurs in subcellular organelles known as chloroplasts, which contain specialized light-absorbing green pigments, the chlorophylls. In the chloroplast, light energy is converted into chemical energy by two different functional units called photosystems. The absorbed light energy is used for electron transfer through a series of electron donor/acceptor compounds. The majority of electrons ultimately reduce NADP+ to NADPH and oxidize H2O to O2. Light energy is also used to generate a proton motive force across the thylakoid membrane, which is used to synthesize ATP. Photosynthesis is a fundamental bioenergetic process that allows production of plant biomass. Photosynthetic carbon fixation and oxygen evolution directly influences the global atmospheric CO2 level and global climate. This chapter provides methods for isolation of chloroplasts and its subcellular fractions and enzymes as well as analytical methods to measure metabolic processes related to photosynthesis.