p. 2138 Photosynthesis The Carbon Reactions
- Lincoln Taiz, Lincoln TaizUniversity of California, Santa Cruz
- Eduardo Zeiger, Eduardo ZeigerUniversity of California, Los Angeles
- Ian Max MøllerIan Max MøllerAarhus University, Denmark
- , and Angus MurphyAngus MurphyUniversity of Maryland
Abstract
This chapter begins by analysing the metabolic cycle that incorporates atmospheric CO2 into organic compounds appropriate for life: the Calvin–Benson cycle. It then considers how the unavoidable phenomenon of photorespiration—a consequence of a side reaction with molecular oxygen—releases part of the assimilated CO2. Because photorespiration decreases the efficiency of photosynthetic CO2 assimilation, the chapter also examines biochemical mechanisms for mitigating the loss of CO2: CO2 pumps, C4 metabolism, and crassulacean acid metabolism. Finally, the chapter briefly looks at the formation of the two major products of the photosynthetic CO2 fixation. These are starch, the reserve polysaccharide that accumulates transiently in chloroplasts, and sucrose, the disaccharide that is exported from leaves to developing and storage organs of the plant.
