light dependent reactions

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33 Terms

1
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where do protons accumulate in chloroplast

thylakoid interior

2
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electron carriers in photophosphorylation

  • platiquinone

  • platocyanin

  • ferredoxin

3
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what is the reduced form of plastoquinone

platoquinol

4
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proton gradient of chloroplast

  • lower conc in stroma

  • higher conc in thylakoid lumen

  • passes through chloroiplast atp synthase

5
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what pigments are found in the photosystems

  • chlorpphyll a and b

  • carotenoids (reflect red and yellow - orange )

6
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what connects psii and psi

cytochrome bf complex

7
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where is the special pair of chlorpohyll molecules found

  • reaction centre

  • active site of photosystem

8
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what happens after excitation of P680*

  • electrons transferred to pheophytin

  • then plastoquinone at site Qa (fixed)

  • to plastoquinone at site Qb (fixed)

9
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how is plastoquinone reduced to plastoquniol

  • second electron reduces mobile plastoquinone

10
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oxygen evolving center

  • water oxidising enzyme

  • water molecule bind to calcium ion and manganese ion

  • 4 manganese ions for every calcium

11
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tyrosine residue

  • facilitates oxygen transfer from P680 to reach chlorophyll residues

12
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photophosphorylation

  • electron tranfer from psii to plastoquinone

  • then cytochrome bf

  • then plastocyanin

  • then psi

  • then ferrodoxin

  • then nadp reductase

13
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resonance energy transfer

  • energy released excites electron from neighbouring pigment

  • energy passes from one pigment to the next

14
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photoinduced charge separation

  • electron transfer from one chlorophyll molecule to another

  • only happens in special pair

15
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what can happen when electrons are excited from ground state to excited state

  • returns to ground - heat or fluorescence released

  • resonance energy transfer

  • photoinduced charge separation

16
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chlorophyll a and b structure

  • contains cyclic tetrapyrrole

  • planar structure (delocalisation of electrons)

  • mg2+ bound to centre

  • one pyrrole ring is reduced

  • highly hydrophobic chain

17
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plastoquinone

  • lipid soluble electron carrier

  • similar structure to ubiquinone

  • chain is hydrophobic so can travel through lipid membrane

18
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reduction of plastoquinone

  • two electrons needed one by one

  • transfer of two eelctrons and two protons from stroma by cytochrome bf complex

  • this happens twice to generate one oxygen, so required 2 molecules of water

  • 4 protons are released

<ul><li><p>two electrons needed one by one</p></li><li><p>transfer of two eelctrons and two protons from stroma by cytochrome bf complex </p></li><li><p>this happens twice to generate one oxygen, so required 2 molecules of water</p></li><li><p>4 protons are released </p><p></p></li></ul><p></p>
19
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plastocyanin

  • blue copper proetin

  • soluble in thylakoid lumen

  • reduced at copper atom

20
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how many molecules of plastocyanin needed to oxidise PQH2

  • 2

21
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what agen is plastocyanin

oxidising

22
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what happens after excitation of P700 in PSI

  • electron transferrred to chlorophyll a0

  • then to phyloquinone

  • then to 3-iron sulphur clusters

  • then ferredoxin

23
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where are electrons finally transferred from photosystem i p700*?

ferredoxin

24
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how does ionised p700* recover?

electrons from plastocyanin

25
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iron sulphur clusters

  • contain cysteine residues

  • each atom of iron is surrounded by 4 atoms of sulphur

  • creates cubic structure

26
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ferredoxin NADP+ reductase

  • catalyses transfer of electrons from ferredoxin to nadp+

  • creates nadph

  • semiquinone formed as intermediate

27
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z-scheme

  • electron transfer to cofactors is energetically favorable

  • electron flow from water to nadph is endergonic process - requires free energy

  • free energy from photons of light at psii (p680) and psi (p700)

28
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are p680* and p700* good oxidising agents or reducing agents?

reducing agents

29
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chlorplast ATP synthase

  • structure with knob (CF1) and stalk (CF0)

  • CF0 - spans the membrane, forms a proton channel for H+ travel from the thylakoid lumen to the stroma

  • CF1 - protrudes into stroma, contains catalytic subunits for ATP synthesis from ADP and Pi

30
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CF0

  • - spans the membrane, forms a proton channel for H+ travel from the thylakoid lumen to the stroma

31
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CF1

  • protrudes into stroma, contains catalytic subunits for ATP synthesis from ADP and Pi

32
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how many photons per atp

2.7

33
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cyclic phosphorylation

  • when no co2 is available or no NADP+, no electrons accepted from ferredoxin

  • cytochrome bf complex used instead

  • protons are pumped but no oxygen or nadph produced

  • 2 photons per atp