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3 Tutorials that teach Light Reaction
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Light Reaction

Light Reaction

Author: Amanda Soderlind

This lesson will give an overview of the light reaction of photosynthesis.

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The first part of photosynthesis is a light dependent reaction meaning it requires light energy from the sun to occur. This part of photosynthesis happens in the chloroplast which is a cellular organelle found only in photosynthetic organisms.  Light from the sun is converted into ATP energy in the process of photosynthesis. Photosystem I and photosystem II are the two parts of the light reaction phase of photosynthesis. Photosystem II occurs before photosystem I.


Photosystem II: electrons are removed from water molecules, oxygen is produced and light from the sun excites chlorophyll electrons which are sent to the electron transport chain.

Photosystem I:  takes in electrons from photosystem II, light excites chlorophyll electrons again, ATP is produced and electrons go through the electron transport chain for a second time to produce NADPH