The Student Room Group
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>
Competition - post a photo you've taken of nature >>

biology photosynthesis - help

Where does the energy to pump protons across the membrane into the thylakoid come from? The textbook i am using is confusing me
it says in the diagram ''using energy from electrons from chlorophyll'
but it says ''the energy to drive the process comes from electrons released when water molecules are split by light - photolysis'' in the actual text
but then it says later that the electrons from water are returned to the chlorophyll molecule. ?


so if someone can please tell me where the energy to pump protons comes from.. i would highly appreciate it. :smile:
Reply 1
Avatar for kkboyk
kkboyk
21
Original post by tmifan
Where does the energy to pump protons across the membrane into the thylakoid come from? The textbook i am using is confusing me
it says in the diagram ''using energy from electrons from chlorophyll'
but it says ''the energy to drive the process comes from electrons released when water molecules are split by light - photolysis'' in the actual text
but then it says later that the electrons from water are returned to the chlorophyll molecule. ?


so if someone can please tell me where the energy to pump protons comes from.. i would highly appreciate it. :smile:


They are all right. When photons of light hit photosystems in Chlorophyll, it excites electrons and these high energy electrons are ejected and travels through series of electron transport chains; in which creates a proton gradient across the thylakoid membrane. Photolysis occurs to replace the lost electrons in the photosystems (inside chlorophyll).

There are two photosystem you should know: photosystem I (which cyclic photophosphorylation occur) and photosystem II (non-cyclic, which produces the proton gradient for the creation of NADP). During cynic photophoshorylation, the electrons ejected from PSI travels through different electron transport chain, and eventually returns back to PSI. As they travel through electron transport chains, energy is released in which is used to make ATP. In non-cyclic photophosphorylation the electrons do not return back to PSI, and travel all the way to PSII (energy released is used to make ATP) which is then energised and then ejected. This is used to drive the formation of reducing power in the form of NADPH.

Quick Reply

Related discussions

Latest

Trending

Trending

Articles for you