how many quanta of lights are required to evolve one oxygen molecule in photosythesis? threee eight four two

how many quanta of lights are required to evolve one oxygen molecule in photosythesis?
  1. threee
  2. eight
  3. four
  4. two

Grade:12th pass

1 Answers

Apoorva Arora IIT Roorkee
askIITians Faculty 181 Points
9 years ago
a total of 8 photons are required for one oxygen molecule.
In thelight reactions, one molecule of thepigmentchlorophyllabsorbs onephotonand loses one electron. This electron is passed to a modified form of chlorophyll calledpheophytin, which passes the electron to aquinonemolecule, allowing the start of a flow of electrons down anelectron transport chainthat leads to the ultimate reduction ofNADPtoNADPH. In addition, this creates a proton gradientacross thechloroplast membrane; its dissipation is used byATP synthasefor the concomitant synthesis ofATP. The chlorophyll molecule regains the lost electron from awater molecule through a process calledphotolysis, which releases adioxygen(O2) molecule. The overall equation for the light-dependent reactions under the conditions of non-cyclic electron flow in green plants is:
2 H2O + 2 NADP++ 3 ADP + 3 Pi+ light → 2 NADPH + 2 H++ 3 ATP + O2
Not allwavelengthsof light can support photosynthesis. The photosynthetic action spectrum depends on the type ofaccessory pigmentspresent. For example, in green plants, theaction spectrum resembles theabsorption spectrumforchlorophyllsandcarotenoidswith peaks for violet-blue and red light. In red algae, the action spectrum overlaps with the absorption spectrum ofphycobilinsfor red blue-green light, which allows these algae to grow in deeper waters that filter out the longer wavelengths used by green plants. The non-absorbed part of thelight spectrumis what gives photosynthetic organisms their color (e.g., green plants, red algae, purple bacteria) and is the least effective for photosynthesis in the respective organisms.

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