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What is the light phase of photosynthesis?

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ajprincess | Student, Grade 10 | Valedictorian

Posted April 29, 2012 at 2:20 AM via web

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What is the light phase of photosynthesis?

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trophyhunter1 | College Teacher | (Level 3) Senior Educator

Posted April 29, 2012 at 1:55 PM (Answer #1)

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Plants absorb light using the pigment chlorophyll during the light reaction. Most of this is captured in leaves and any other green parts of a plant. Algae can also carry out photosynthesis.  One molecule of chlorophyll absorbs one photon of light and loses an electron. This electron goes to pheophytin, to quinone to start the flow of electrons down an electron transport chain. Eventually, NADP is converted to NADPH in plants, which is a reduction reaction. This will create a photon gradient across the chlorplast membrane. Then, ATP synthase which is an enzyme, synthesizes ATP. After water is split due to photolysis, an electron is regained by the chlorophyll. The oxygen released from splitting water, combines with another oxygen to form an O2 molecule. This is released by the stomates in the leaves to the atmosphere. The hydrogen from the water, will combine with the carbon dioxide in the leaf during the light independent reactions, to form the carbohydrate glucose.

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sweetgiggles | Student , Grade 10 | Salutatorian

Posted April 29, 2012 at 8:03 AM (Answer #2)

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During the light dependent phase of photosynthesis, light energy from the sun is harvested by special pigments on the thylakoid membranes of the chloroplasts. Chlorophyll (specifically chlorophyll a) is the most important of these pigments. The pigments are not arranged haphazardly on the surface of the chloroplast but in specific aggregates known as photosystems. The photosystems play a central role in the light dependent phase of photosynthesis. In the light dependent reaction of photosynthesis, an energy-rich electron from a special chlorophyll molecule in a photosystem is passed along a chain of molecules known as the electron transfer system in a process called photophosphorylation. The energy lost by the electron, as it moves along the chain, is used to make ATP. .............

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