Question

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1.) The photosystem of purple bacteria absorbs light at 870 nm. (a (3 pts) Calculate the energy of one mole of photons (1 einstein) of light 1 - 870 nm. (b) ( 3 pts) How many moles of ATP under standard conditions could be theoretically synthesized using this energy? (c) (3 pts) Does this photosystem evolve Oz? Why or Why not? (d) (3 pts) The purple bacteria photoreaction center catalyzes the following reaction: 2 Cycz(Fe)+Q+ 2H + 2 Cytcz(FeS) + QH2 Cytcz(Fe'))+ e -Cytc (Fe) or=0.254 V Q+ 2e + 2H - QH $=0.060 V Use the given reduction potentials to calculate AFT,AG" and Ko (e) (3 pts) How does The purple bacteria photoreaction center make this electron transport exergonic?

Answer 1

a) Calculating energy of 1 mole of photone) In purple bacteria the photosynthetic materials  are present on the bacterias lipid bilayer cytoplasmic membrane and it is surrounded by more permeable membrane that is cell wall. During the photoraction centre it capture light and act as driving force to seperate charge from reduced cytochrome and it passes this to quinone. The reduced quinone thus formed reacts with the transmembrane cytochrome bc1 complex via a Q cycle and  pump protons to the bacterial membrane and returns the electrons to the cytochrome. This proton motive force is used for the production of ATP. In purple bacteria electrons flows as cyclic way through the photosynthetic electron transfer pathway and the generated electrons are transferred to NADP, for the synthesis of  NADH . In the photoreaction center the electrons are generated from oxidised chlorophyll which comes from hydrogen gas. Thus it is exergonic process as elctron flow to surrounding are positive flow of energy for the occurence of photochemical reaction.

- la) To calculate energy of Imole of photore of light formula Energy of photon speed of light & Planch's constant wavelength energy of photon speed of light = 3 x 108 mis Planck's constant = 663x10-34 2 - 810nm - 8Toulo-am Potting, the values in the equation: Energy of photon = 3x108 x 663x10.34 &lox lo-9 = 19.89x10 -34 + 8 + 9 870 - 0.0228 x 10" = 2.28x10-19 Joules for calculating Imole of photon we multiply it with Avagadro number Energy of mole - Energy of particle x 6.02x10 23 of photon – 2.28x10-12 & 6.02x10 2 3 13 12 x 10 Jouls