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The Light-Dependent Reaction
The light-dependent reaction of photosynthesis involves the capture of light whose energy is used for
two purposes:

To add an inorganic phosphate molecule to ADP thereby making ATP
To split water by the process of photolysis, into H+ ions and OH- ions

The reaction needs light energy.…

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Photolysis of Water
The loss of electrons when light strikes a chlorophyll molecule leaves it short of electrons.
If the chlorophyll molecule is to continue absorbing light energy, these electrons must be replaced.
The replacement electrons are provided from water molecules that are split using light energy.
This photolysis of…

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1. Light energy hits photosystem 2
This light energy excites the electrons and causes the chlorophyll to lose electrons
These electrons must be replaced
Light energy also causes water to split into protons, electrons and oxygen
The electrons from photolysis are used to replace the electrons lost from the chlorophyll…

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Chemiosmosis is the name of the process where the movement of H+ ions across a membrane generates
ATP ­ this also occurs in respiration.

The excited electrons lose energy as they move along the electron transport chain.

This energy is used to transport protons into the thylakoid so that the…


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