Photosynthesis- Light-dependant stage

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What is non-cyclic photophosphorylation?
The type of photophosphorylation that involves 2 photosystems
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Describe the 2 photosystems involved in non-cyclic photophosphorylation
Photosystem 1 and photosystem 2, where photosystem 1's reaction centre absorbs a higher wavelength than photosystem 2's reaction centre
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Once light has been absorbed by photosystem 2 (step 1) what happens next?
The excited electron are released into an electron transport chain, releasing ATP from chemiosmosis
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What happens in photosystem 2 after the excited electrons have left?
It replaces lost electrons by splitting water molecules (photolysis)
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What happens at photosystem 1, whilst stage 1 is occuring?
The sunlight excites electrons in photosystem 1 where they are also released into another electron transport chain (more chemiosmosis)
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How does the photosystem 1 replace the lost electrons?
By taking up the electrons from photosystem 2 from the electron transport chain
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What happens after the electrons from photosystem 1 have passed through the electron transport chain?
They are taken up by the coenzyme NADP, along with a hydrogen ion forming reduced NADP
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What is photolysis?
The splitting of water molecules into hydrogen ions, electrons and oxygen, using energy from the sunlight.
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Name the enzyme involved in photolysis
Oxygen-evolving complex (found in photosystem 2)
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How does photolysis allow ATP synthesis to occur?
The hydrogen protons released during photolysis are released into the thylakoid lumen, this increases the proton concentration gradient so when they move back down through channels, they drive the synthesis of ATP
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What is the by-product released from photolysis?
Oxygen
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How is reduced NADP produced?
When the hydrogen ions return into the stroma, it combines with NADP to from reduced NADP, removing the hydrogen atoms from the stroma and maintaining the concentration gradient
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What is cyclic photophosphorylation?
Where there is only one photosystem involved, the electrons go through the electron transport chain and then returned to the photosystem 1 again, instead of being used to make reduced NADP
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Other cards in this set

Card 2

Front

Describe the 2 photosystems involved in non-cyclic photophosphorylation

Back

Photosystem 1 and photosystem 2, where photosystem 1's reaction centre absorbs a higher wavelength than photosystem 2's reaction centre

Card 3

Front

Once light has been absorbed by photosystem 2 (step 1) what happens next?

Back

Preview of the front of card 3

Card 4

Front

What happens in photosystem 2 after the excited electrons have left?

Back

Preview of the front of card 4

Card 5

Front

What happens at photosystem 1, whilst stage 1 is occuring?

Back

Preview of the front of card 5
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