Photolysis of water

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  • Created by: sophiee96
  • Created on: 13-08-13 09:48
What happens when light strikes a molecule at the reaction centre of photosystem II?
An electron is raised to a higher energy level and leaves the chlorophyll molecule short of electrons
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What must happen if the chlorophyll molecule is to continue absorbing light energy?
It needs to replace the lost electrons
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The replacement of electrons are provided from what?
Water molecules that are split using light energy
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What do the protons do?
Combine wih electrons from photosystem I and NADP to give reduced NADP
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How can the photolysis of water be demonstrated?
Using the Hill reaction
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Robert Hill used isolated chloroplasts to demonstrate what?
That they have the reducing power to evolve oxygen from water in the presence of an oxidising agent
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It is possible to repeat this using the blue dye DCPIP which acts as a substitute for what?
The plants NADP
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What happens to the DCPIP when reduced?
It becomes colourless
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Cyclic photophosphorylation involves which photosystem?
Photosystem I
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Light energy is absorbed by PSI, then what happens?
It is passed to chlorophyll a at the reaction centre
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What happens to the electrons?
They are passed to a higher energy level where they are received by the second electron centre
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What happens to the electrons that aren't used up in the production of reduced NADP?
They pass along a chain of electron carriers before being returned to PSI
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What happens as the electron passes along the chain of carriers?
Sufficient energy is generated to make ATP
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Is any reduced NADP produced in this process?
No
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Where do the reactions of the light-dependent stage of photosynthesis take place?
In the thylakoid membranes of the chloroplast
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Electrons flow along the chain of electron carriers from where to where?
PSII to PSI
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What does this flow of electrons provide the energy for?
To pump hydrogen ions from the stroma, across the thylakoid membrane and into the thylakoid space
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What does this result in?
An electrochemical gradient
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Why?
Because there are more hydrogen ions inside the thylakoid space than outside the stroma
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What do hydrogen ions then do?
Flow along this gradient across the thylakoid membrane through the protein channels
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This produces energy for what?
The formation of ATP by ATP synthetase
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Other cards in this set

Card 2

Front

What must happen if the chlorophyll molecule is to continue absorbing light energy?

Back

It needs to replace the lost electrons

Card 3

Front

The replacement of electrons are provided from what?

Back

Preview of the front of card 3

Card 4

Front

What do the protons do?

Back

Preview of the front of card 4

Card 5

Front

How can the photolysis of water be demonstrated?

Back

Preview of the front of card 5
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