Photosynthesis light-dependent reactions

Figure 12.8 The Z scheme, an overview of the flow of electrons during the light-dependent reactions of photosynthesis. ED and EA refer to the electron donors and acceptors of the two photosystems, respectively...

NADPH and ATP are produced in the light-dependent reactions of photosynthesis in about the same ratio (2 3) as they are consumed in the Calvin cycle. Nine ATP molecules are converted to ADP and phosphate in the generation of a molecule of triose phosphate eight of the phosphates are released as Pj and combined with eight ADP to regenerate ATP. The ninth phosphate is incorporated into the triose phosphate itself. To convert the ninth ADP to ATP, a molecule of Pj must be imported from the cytosol, as we shall see. 

The cost of fixing three C02 into one triose phosphate is nine ATP and six NADPH, which are provided by the light-dependent reactions of photosynthesis. 

The pigments and proteins responsible for the light-dependent reactions of photosynthesis are found within thylakoid membrane (Figure 13.3). Most of these molecules are organized into the working units of photosynthesis. 

Fig. 11.5 Photochemical electron transport chain in a Z-scheme during light-dependent reactions of photosynthesis. EA and ED refer to the electron acceptor and electron donor of the two photosystems. Adapted with permission from (Wardle B, 2009 Principles and Applications of Photochemistry, Wiley, p. 226). Cop5oight (2009) John Wiley Sons...

Bacterial Photosynthesis A light-dependent, anaerobic mode of metabolism. Carbon dioxide is reduced to glucose, which is used for both biosynthesis and energy production. Depending on the hydrogen source used to reduce COj, both photolithotrophic and photoorganotrophic reactions exist in bacteria. 

FIGURE 22.4 The light-dependent and light-independent reactions of photosynthesis. Light reactions are associated with the thylakoid membranes, and light-independent reactions are associated with the stroma. 

In the light-dependent part of photosynthesis—the light reactions H2O molecules... 

N. Rigopoulos, and R. C. Fuller The pyruvate phosphoclastic reaction and light-dependent nitrogen fixation in bacterial photosynthesis. Proc. Nat. Acad. Sci. (U. S.) 52, 762-768 (1964). 

---