Photosynthesis-Light Dependent

The Light Dependent Reaction  Requires light energy  Takes place in the Thylakoid membranes  Light energy is absorbed by the photosynthetic pigments in the photosystems and converted into chemical energy  Light energy used to convert ADP and Pi into ATP and to reduce NADP

Photophosphorylation  Light dependant reaction absorbs light energy in the photosystems for three things  1) Producing ATP from Pi and ADP. This is called photophosphorylation.  2) Making reduced NADP from NADP  3) Photolysis of water to produce protons (H+ ions), electrons and oxygen

Non-cyclic Photophosphorylation  The Photosystems and electron carriers form an electron transport chain  Light energy exites electrons in chlorophyll 2  Photolysis of water (H2O 2H* + 1/2 O2) due to Electrons lost needing to be replaced. Energy from the exited electrons produces ATP The energy lost is used to transport protons into the thylakoid Protons move down their concentration gradient via ATP synthase. The energy from this movement forms ATP from ADP and an inorganic phosphate Reduced NADP is generated Light energy is absorbed by ps1 Electrons transferred to NADP, along with a proton from the stroma to form reduced NADP

Cyclic Photophosphorylation  Only produces ATP whereas Non-cyclic Photophosphorylation produces Reduced NAPD and O2 as well  Only uses PS1  Electrons from the chlorophyll molecule are not passed onto NADP, They are passed back to PS1 via electron carriers