Name: ID #: 27, (a) Calculate the energy required to move electrons through the
ID: 259296 • Letter: N
Question
Name: ID #: 27, (a) Calculate the energy required to move electrons through the Z-scheme of photosynthesis. (b) What supplies this energy? t(VI Cytochrome a, (Fe"1+e cytochrome a, (F Cytochrome @ CFe**) + e-ts cytochrome ?Fe'*) Cytochrome c (Fe"1tcytochrome c(F Cytochromec,(Fe1+cytochromec,(Fel Cytochrome b (Fe'1cytochrome b(Fe" Imitochondrial) Ubiquinone+2H+ubiquinol Fumarate2H 2esuccinate FAD +2H +eFADH, lin flavoproteinsl Oxaloacetate2H +2emalate Pyruvate"2H2elactate Acetaldehyde +2H+2e ethanol FAD+2HADH2 lfree coenzyme) -0.166 -0.185 -0.197 Lipoic acid +2H +2edihydrolipoic acid NAD +H+2eNADH NADP H +2eNADPH Cysteine disulfide+2H +22ysteine 0.515 -0.581 Acetate 3H +2eacetaldehyde + 10-11 of 11Explanation / Answer
The Z-scheme occurs in light reactions, showing the pathway of electron transport from water to NADP+ (nicotinamide adenine dinucleotide phosphate). there is release of oxygen, the "reduction" of NADP+ to NADPH (by adding two electrons and one proton), and the building-up of a high concentration of hydrogen ions inside the thylakoid lumen (needed for ATP production).
The Z scheme shows the pathway of electron transfer from water to NADP+. Using this pathway, plants transform light energy into "electrical" energy (electron flow) and hence into chemical energy as reduced NADPH and ATP.
2 H2O + 2 NADP+ +10 H+ ? O2 + 2 NADPH + 12H+
Energy is required in transfer of electrons from P680 to Pheo and from P700 to AO, after concumption of light. The Z scheme for photosynthesis requires that the photosystems operate in series to transfer electrons from H2O to ferredoxin. 4 e- must be transferred to evolve 1 O2, 8 photons are required for the evolution of 1 O2 molecule with a concurrent build up of 8 H+/e- inside the thylakoid membrane. Alongwith this it is generally accepted that 1 H+/e- is transported froni outside to inside the thylakoid membrane during intersystem electron flow. In 3 H+/ATP stoichiometry for the CF0-CF1 ATP synthetase complex, then the oxygen-evolving light reactions of photosynthesis provide 2NADPH + 2 67ATP.
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