Light Reaction

light reaction occur in thylakoid membrane or grana...
there are two types of photosystem....

• photosystem i (P700)
• photosystem ii (P680)

Light Reaction.

• Light reaction occur in grana.
• Chlorophyll molecule absorb/trap light energy.
• Energy absorbed transferred to reaction centre of Photosystem (ii) P680, P680 is photoactivated.
• Electron become excited and move to primary acceptor.
• The electron is transferred down the energy level through a series of electron carries.
• Among the electron series carries are plastocyanin, chytochrome complex, plastoquinone.
• When electron transferred don the energy level, energy is released which is used for phosphorylation process which ADP+P_i = ATP.
• Electron finally transferred to P700, the reaction centre of PS (i).
• Molecules in PS I also absorb light energy.The energy transferred to reaction centre of PS (i).PS (i) is photoactivated.
• The electron become excited and move to primary acceptor.
• Then the electron transferred to through a finally electron series that is NADP is converted into NADPH+H⁺. This pathway considered as non-cyclic phosphorylation.
• The cyclic phosphorylation is the chlorophyll molecule absorb light energy.The photosysytem I activated.
• The electron become excited and move to primary acceptor.
• Then the electron is transferred through a electron series carries. Among the electron series carries are cytochrome complex, and plastocyanin.
• Finally, the electron move back tp Photosystem (i).