Question

6. Label and describe each step in the light-dependent reactions including all of the electron receptors.

Answer 1

These are called light reactions as they require light to initiate the reactions ,Light reactions occurs in the thylakoids of chloroplast ,it consists of two photosystems,between this two photosystems there is electron transport chain.

1.when light hits photosystem-II which had many pigments mainly chlorophyll -a ,helps in the absorption of the light ,the electrons get excited and moves across the electron transport chain ,when water is uptaken the energy from the light is used to split water molecule in to hydrogen and oxygen(by product),

2.The excited electrons travel through transport chain which pumps hydrogen ions in to thylakoid space,

3.Electrons reaches the photosystem-I from transport chain,the excited electrons of photosystem-I are transferred to final electron acceptor called NADP+,it becomes reduced by accepting the hydrogen to NADPH,

4.H+ accumulation stimulates chemiosmosis ,this ions moves and migrate to ATP synthase to form ATP from ADP.

The transfer of electrons from photosystem-II to photosystem-I includes series of receptors are :

photosystem-II--pheophytin,---plastoquinone,---cytochromeb6/f complex,----plastocyanin--- photosystem -I--phylloquinone--ferrodoxin----flavoprotein---NADP