Light-independent reactions, of photosynthesis

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 chloroplasts a double membrane encloses an inner space called the stroma. The stroma contains the enzymes that catalyze the light-independent reactions of photosynthesis. 

The Z scheme is a mechanism whereby electrons are transferred from water to NADP +. This process produces the reducing agent NADPH required for fixing carbon dioxide in the light-independent reactions of photosynthesis. Removal of the electrons from water also results in the production of oxygen. As electrons flow from PSII to PSI, protons are... 

Calvin, Melvin (1911-97) USblochemlst After World War 11, at the Lawrence Radiation Laboratory, Berkeley, he investigated the light- independent reactions of photosynthesis. Using radioactive carbon-14 to label carbon dioxide, he discovered the... 

What reactions occur during the light-independent reactions of 17. photosynthesis ... 

With very few exceptions, life directly or indirecdy depends on photosynthesis. The electric current is the flow of electrons from water to NADP+ a light-requiring process. The current continues in the light-independent reactions, with electrons flowing from NADPH to 6 phosphoglycerate, which ultimately yields glucose. 

What other light-independent partial reactions of photosynthesis could we seek in maize etioplasts Jagendorf and Uribe demonstrated that thylakoids of spinach form ATP from ADP and inorganic phosphate when they are transferred from an acidic to an alkaline solution. The formation of ATP during acid-to-base transition (A/B) requires no light. In fact, the reaction is generally carried out in the presence of p-chlorophenyl-1,1-dimethyl urea (CMU), a powerful inhibitor of photosynthesis, to prevent photophosphoiylation. 

Fig. 11. Top left Description for a reaction pathway in which C-P430" is photoaccumulated in the reaction center of green-sulfur bacterium Chlorobium tepidum in the presence of 2uM mPMS. The right panel shows flash-induced absorbance changes of charge recombination in the dark. Lower left panel shows various light-induced difference spectra (a) the maximum flash-induced absorbance change in the absence of m-PMS (b) spectrum of the m-PMS independent component (c) is (b) expanded 5-fold. Both panels are reproduced from Kusumoto, Inoue and Sakurai (1995) Spectroscopic studies of bound cytochrome c and an iron-sulfur center in a purified reaction centerfrom the green suifur bacterium Chlorobium tepidum. Photosynthesis Res 43 109.

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