Light dependent reaction

  • Created by: Hindleyc
  • Created on: 24-11-18 22:28
What does it involve?
Capture of light energy to add inorganic phosphate (Pi) to ADP to make ATP and to split water into H+ ions (protons) and OH- ions.
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What is this splitting of water caused by?
Light and so if referred to as photolysis
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What 3 products does the LDR produce?
ATP, Reduced NADP and oxygen- non cyclic
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When a substance loses electrons, combines with oxygen or loses hydrogen (energy is given out)
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When a substance gains electrons, loses oxygen, or gains hydrogen (energy is taken in)
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Making ATP?
Chlorophyll molecule absorbs light energy in p2, Energy level of 2 electrons raised and the electrons leave the chlorophyll molecule and pass to an electron carrier
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Energy to phosphorylate ADP
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How is water split?
using light energy
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What does this yield?
Hydrogen ions (protons) electrons and oxygen
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2H2O= 4H+ + 4E- + O2
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How is light also absorbed?
By chlorophyll in photosystem 1
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What happens next?
Electrons leave this molecule and again pass down a series of carriers
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What are they used together with?
Hydrogen ions from the photolysis of water to produce reduced NADP
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What does the oxygen produced do?
Either used in respiration or diffuses out of the leaf as a waste product
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1st step&2nd
photons of light hitting accessory pigments passed to primary pigments raised energy level in chlorophyll A molecule loses e-=photoionisation and chlorophyll oxidised
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step 3,
electrons picked up by primary electron acceptor- protein sat in thylakoid membrane close to where c A molecule is- same energy level.
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passes down ETC of progressively lower energy level so e- reduce in energy level so e- carriers release energy lost to generate ATP in chemiosmosis
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e- lost from p2 replaced by e- from photolysis where water split into 3 parts
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6(for p1)
repeat 1-3
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picked up by carrier NADP combine with 2H+ to reduce NADPneeded for LIR
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Where does p1 receive its replacement electrons from?
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ATP, reduced NADP
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What is this used in?
LIR transported into storm to convert inorganic CO2 into COH carbohydrate using ATP
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What builds up H+ gradient in chemiosmosis?
Pump h+ ions in and photolysis builds up high conc h+ in thylakoid space. then 2h+ + 2e- + NADP = NADPH
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/Step 1 of chemiosmosis?
energy from electrons moving down etc is used by proton pump to AT h ions into inter-thylakoid space
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H ions from photolysis also contribute to the proton gradient
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h ions move through ATP synthase channel (only way through)/pathway changing its configuration leading to synthesis of ATP from ADP and Pi
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Card 2


What is this splitting of water caused by?


Light and so if referred to as photolysis

Card 3


What 3 products does the LDR produce?


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Card 4




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