Photons Photosynthesis

In turn, the latter species is believed to be the cytotoxic agent that results from the application of methyl viologen on plants engaged in photosynthesis (photon-driven electron transfer).39... 

While this electron flow takes place, the cytochrome on the periplasmic side donates an electron to the special pair and thereby neutralizes it. Then the entire process occurs again another photon strikes the special pair, and another electron travels the same route from the special pair on the periplasmic side of the membrane to the quinone, Qb, on the cytosolic side, which now carries two extra electrons. This quinone is then released from the reaction center to participate in later stages of photosynthesis. The special pair is again neutralized by an electron from the cytochrome. 

The quantum yield of photosynthesis, the amount of product formed per equivalent of light input, has traditionally been expressed as the ratio of COg fixed or Og evolved per quantum absorbed. At each reaction center, one photon or quantum yields one electron. Interestingly, an overall stoichiometry of one translocated into the thylakoid vesicle for each photon has also been observed. Two photons per center would allow a pair of electrons to flow from HgO to NADP (Figure 22.12), resulting in the formation of 1 NADPH and Og. If one ATP were formed for every 3 H translocated during photosynthetic electron transport, 1 ATP would be synthesized. More appropriately, 4 hv per center (8 quanta total) would drive the evolution of 1 Og, the reduction of 2 NADP, and the phosphorylation of 2 ATP. 

Phosphine(s), chirality of, 314 Phosphite, DNA synthesis and, 1115 oxidation of, 1116 Phospholipid, 1066-1067 classification of, 1066 Phosphopantetheine, coenzyme A from. 817 structure of, 1127 Phosphoramidite, DNA synthesis and, 1115 Phosphoranc, 720 Phosphoric acid, pKa of, 51 Phosphoric acid anhydride, 1127 Phosphorus, hybridization of, 20 Phosphorus oxychloride, alcohol dehydration with. 620-622 Phosphorus tribromide, reaction with alcohols. 344. 618 Photochemical reaction, 1181 Photolithography, 505-506 resists for, 505-506 Photon, 419 energy- of. 420 Photosynthesis, 973-974 Phthalic acid, structure of, 753 Phthalimide, Gabriel amine synthesis and, 929... 

Suppose that the photosynthesis reaction (20b) in Chapter 24 (p. 430) could be based upon light of wavelength 2400 A (this light is absorbed heavily by ozone). How many moles of these photons would provide the 673 kcal of energy needed to produce one mole of glucose (Remember, E = hv, and h = 9.5 X 10 14 kcal sec/mole). Compare your answer with that of Exercise 24-10. 

Measured end points are photosynthesis as the incorporation of radiolabelled H C03 ( C) and bacterial activity as the incorporation of radiolabelled thymidine (thym) fluorometric measurements basal fluorescence (Fo) and photon yield (Y) chlorophyll-a concentration (chl-a) species composition (spp) and the biovolume of algae obtained after algal counting (biovolume)... 

Bjorkman, O. (1987). Low-temperature chlorophyll fluorescence in leaves and its relationship to photon yield of photosynthesis in photoinhibition. In Photoinhibition, ed. D.J. Kyle, C.B. Osmond and C.J. Arntzen, pp. 123-44. Amsterdam Elsevier. 

In photosynthesis, the reaction involves eight photons for each oxygen molecule, each with an energy of about 1.8 eV (175kJ/mol). Hence the efficiency of... 

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