Light-dependent stage of photosynthesis

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  • Created by: sophiee96
  • Created on: 12-08-13 10:44
The reactions of the light-dependent stage occur where?
In the thylakoid membrane of the chloroplasts
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What is the first stage?
Photolysis
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What does photolysis involve?
The splitting of water molecules by light
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What does the splitting of water by light produce?
Hydrogen ions and electrons
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What occurs after photolysis?
The synthesis of ATP
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What does the synthesis of ATP form?
ADP and Pi
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What is this type of phosphorylation known as?
Photophosphorylation
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Why?
Because light energy is involved
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What happens to the hydrogen ions?
They combine with NADP to produce reduced NADP
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What happens when light strikes a molecules at the reaction centre?
An electron is raised to a higher energy level
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What does this do?
Sets up a flow of electrons
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What is the electron flow known as?
The 'Z-scheme'
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What are the two ways ATP can be synthesised?
Non-cyclic photophosphorylation and cyclic-photophosphorylation
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Non-cyclic photophosphorylation involves which photosystems?
Photosystem I and photosystem II
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What happens first?
Photons of light are absorbed by photosystem II
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The photons of light are then passed to what?
Chlorophyll a in the reaction centre
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What does this cause?
The displacement of two 'excited' electrons
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What happens to the two high energy electrons?
They are picked up by electron acceptors
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What do these electron acceptors do?
Pass the electrons along a chain of carriers through a proton pump and to photosystem I
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What is the energy lost by the electrons used for?
To convert ADP to ATP
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What happens to photons of light that are absorbed by photosystem I?
They are passed to chlorophyll a in the reaction centre
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What does this cause?
Two electrons to be emitted and raised to a higher energy level
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What happens to these electrons?
They are picked up by another electron acceptor
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Photosystem II is not unstable, why?
Because it has lost electrons
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When are these replaced?
When electrons become available from the splitting of water by photolysis
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During photolysis a water molecule dissociates into what?
Electrons, hydrogen ions and oxygen
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The second electron acceptor (receives electrons from PS I) passes some of these electrons where?
To hydrogen ions on the outside of the thylakoid membrane
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What do the electrons do then?
Reduce NADP
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Why is this method of ATP production called non-cyclic photophosphorylation?
Because these electrons are not recycled back into the chlorophyll
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Other cards in this set

Card 2

Front

What is the first stage?

Back

Photolysis

Card 3

Front

What does photolysis involve?

Back

Preview of the front of card 3

Card 4

Front

What does the splitting of water by light produce?

Back

Preview of the front of card 4

Card 5

Front

What occurs after photolysis?

Back

Preview of the front of card 5
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