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Cyclic photophosphorylation
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The Illuminati
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#1
Is the reason why this doesn't produce NADPH and only a small amount of ATP due to the fact that it only involves PSI therefore photolysis doesn't occur to produce protons so there aren't enough protons to make any NADP or much ATP.
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123emily
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The same electrons are recycled back into PSI via a electron carrier, making a cycle. So the electrons don't go along the rest of the electron transport chain to end up in the stroma which means they aren't available to reduce NADP. The ATP is made in this by the ATP Synthase enzyme that combines ADP and an inorganic phosphate group together.
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Alexok
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#3
What benefits would cyclic phosphorylation have for the plant, or why does it begin to happen
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The Illuminati
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#4
(Original post by 123emily)
The same electrons are recycled back into PSI via a electron carrier, making a cycle. So the electrons don't go along the rest of the electron transport chain to end up in the stroma which means they aren't available to reduce NADP. The ATP is made in this by the ATP Synthase enzyme that combines ADP and an inorganic phosphate group together.
The same electrons are recycled back into PSI via a electron carrier, making a cycle. So the electrons don't go along the rest of the electron transport chain to end up in the stroma which means they aren't available to reduce NADP. The ATP is made in this by the ATP Synthase enzyme that combines ADP and an inorganic phosphate group together.
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The Illuminati
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#5
(Original post by Alexok)
What benefits would cyclic phosphorylation have for the plant, or why does it begin to happen
What benefits would cyclic phosphorylation have for the plant, or why does it begin to happen
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Alexok
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123emily
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#7
(Original post by The Illuminati)
How do you make ATP with no proton gradient
How do you make ATP with no proton gradient
Are you sure photolysis doesn't occur in cyclic photophosphorylation? I can't think of where else they would come from
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The Illuminati
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#8
(Original post by 123emily)
The diagram I have in my revision book shows H+ ions being taken into the stroma by ATP Synthase in the same way as Non-cyclic photophosphorylation (in chemiosmosis to generate ATP) but I'm not sure where the protons come from.
Are you sure photolysis doesn't occur in cyclic photophosphorylation? I can't think of where else they would come from
The diagram I have in my revision book shows H+ ions being taken into the stroma by ATP Synthase in the same way as Non-cyclic photophosphorylation (in chemiosmosis to generate ATP) but I'm not sure where the protons come from.
Are you sure photolysis doesn't occur in cyclic photophosphorylation? I can't think of where else they would come from
Is your revision book CGP?
????
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123emily
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#9
(Original post by The Illuminati)
My textbook and a load of mark schemes say cyclic= no photolysis.
Is your revision book CGP?
????
My textbook and a load of mark schemes say cyclic= no photolysis.
Is your revision book CGP?
????
Yeah it's CGP
I really don't know where the protons come from then but that's how it shows generation of ATP in cyclic photophosphorylation in the CGP book
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The Illuminati
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#10
(Original post by 123emily)
Oh right
Yeah it's CGP
I really don't know where the protons come from then but that's how it shows generation of ATP in cyclic photophosphorylation in the CGP book
Oh right
Yeah it's CGP
I really don't know where the protons come from then but that's how it shows generation of ATP in cyclic photophosphorylation in the CGP book
Oh well let's just hope that there isn't an 8 mark question on that.
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123emily
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#11
(Original post by The Illuminati)
My CGP book shows H+ too.
Oh well let's just hope that there isn't an 8 mark question on that.
My CGP book shows H+ too.
Oh well let's just hope that there isn't an 8 mark question on that.
and I really hope because it's not in the books that we don't need to know it for the exam
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Joe1995
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#12
Cyclic photophosphorylation occurs when there is no NADP available to act as the final electron acceptor. So the electron from photosystem 1 replaces itself. Hence why only ATP is produced in cyclic photophosphorylation and not Reduced NADP.
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shakerlicious
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#13
If I remember correctly, cyclic photophosphorylation is used when there is not enough ATP produced in the light dependent phase for the calvin cycle. Without sufficient ATP, the calvin cycle would stop. Also, NADPH2 would begin to build up. So in cyclic photophosphorylation, only photosystem I is used, and the electrons released from it is recycled back to the same photosystem. This process produces ATP but not NADPH2. Hope this helps 
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