Light reaction

overview

occurs in thylakoids, captured light energy from the sun is converted to the chemical energy of Atp and the high-energy electron carrier NADPH, water is electron source,

1st step

light absorbtion by photosystem II

Light absorbtion

sunlight hits chlorophyll inside photosystem II, light excites electron in chlorphyll to higher energy level, those excited electrons go to electron transport chain.

2nd step

splitting of water (photolysis)

splitting of water (photoysis)

to replace excited electrons that left PsII, water molecules are split. It produces Electrons- replace the lost ones in PSII, hydrogen ions- used later to make ATP, oxygen- released as a byproduct

3rd step

Electron Transport Chain

Electron Transport Chain

the excited electrons move along a series of proteins in thylakoid membrane. as moving they release energy which is used to pump H ions into thylakoid space, creating proton gradient

4th step

ATP formation

Atp formation

high concentration of H inside the thylakoid pushes protons through an enzyme called ATP synthase. As H ions flow through ATP synthase makes atp from adp +P. (photophosphorylation

5th step

Photosystem I and NADPH formation

Photosystem I and NADPH formation

the electrons continue to Photosystem I, where they get re-energized by snlight. These electrons are finally transferred to NADP, along with H ions, forming NADPH

end products of light reaction

ATP (energy for calvin cylce), NADPH (proves electrons for making sugars), Oxygen (released into the atmosphere)