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Electron Transfer Chain

Can someone please explain to me how the ETC is used to form ATP in the chloroplast?
aiman
Can someone please explain to me how the ETC is used to form ATP in the chloroplast?
Isn't that in plant cells? I'm not sure then, because whilst I could easily answer your question if you're referring to the ETC in mitochondria, I don't think I'll be able to this time :s:

Just because I'm studying human physiology atm and that's what we're looking at.

Perhaps this site might help you though: http://www.cellsalive.com/cells/chloropl.htm
Reply 2
Avatar for tomtheone
tomtheone
2
I really think aiman must be talking about the electron transfer chain in the mitochondria. I have not heard anything about electron transfer happening in the chloroplasts
Reply 3
Avatar for doogleboy
doogleboy
The electron transfer chain does occur in chlorplasts, in the light-dependent stage of photosynthesis. Electrons in chlorophyll are excited by photons of light and they reach the reaction centre, from which they acheive a higher energy level. The electrons then pass down electron carriers (cytochrome complexes), each carrier at a lower energy level than the previous one. This means that energy is released down the chain. This energy is used to pump H+ ions from the stroma into the thylakoid membrane causing a proton gradient (electrochemical gradient) to build up. The protons then diffuse down this gradient through ATP synthase molecule in the thylakoid membrane, producing ATP from ADP and Pi. The ATP is then passed to the light-independent stage of photosynthesis (Calvin cycle).
Reply 4
Avatar for WokSz
WokSz
17
There are two ways chlorophyll can be photoactivated:

Non-Cyclic Photophosphorylation:
Light is abosorbed by both PS (photosystem) 1 and 2. Electrons are excited and ommitted from these respective PSs. Instead of falling back into the chlorophyll and losing its energy as fluroescence (sp?), the electrons are captured by Electron carriers, and passed to the ETC. Enough energy is released for synthesis of ATP.

Cyclic Photophosphorylation
Light excites electron (e-) in P700 - this is emitted from the chlorophyll molecule.
This Electron is then captured by an electron acceptor, and passed along the ETC. Enough energy is released to synthesize ATP from ADP+Pi.
Reply 5
Avatar for aiman
aiman
OP
12
The electron transfer chain does occur in chlorplasts, in the light-dependent stage of photosynthesis. Electrons in chlorophyll are excited by photons of light and they reach the reaction centre, from which they acheive a higher energy level. The electrons then pass down electron carriers (cytochrome complexes), each carrier at a lower energy level than the previous one. This means that energy is released down the chain. This energy is used to pump H+ ions from the stroma into the thylakoid membrane causing a proton gradient (electrochemical gradient) to build up. The protons then diffuse down this gradient through ATP synthase molecule in the thylakoid membrane, producing ATP from ADP and Pi. The ATP is then passed to the light-independent stage of photosynthesis (Calvin cycle).
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Thank you :smile:
Reply 6
Avatar for nikk
nikk
15
Yup, plus plants also respirate by oxidative phosphorylation in the same way we do (i.e. they also have mitochondria).

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