Doodlegirl
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I was wondering if anybody had access or knew where to find some revision questions on unit 4 Biology AQA? Some for each topic would be great. I have already exhausted all the past papers and the text book. (Moks don't cha know) Mark schemes to go with the questions would be much appreciated.

Thanks
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TSRuserrr9
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(Original post by Doodlegirl)
I was wondering if anybody had access or knew where to find some revision questions on unit 4? Some for each topic would be great. I have already exhausted all the past papers and the text book. (Moks don't cha know) Mark schemes to go with the questions would be much appreciated.

Thanks


What subject and what level?
If you mean Aqa a2 Biology unit 4 then BUMPPPPPPPPP

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Doodlegirl
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(Original post by TSRuserrr9)
What subject and what level?
If you mean Aqa a2 Biology unit 4 then BUMPPPPPPPPP

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Oh dear forgot to put that in duh, see this is what Moks do to you :P. Biology AQA it is hahaha
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TSRuserrr9
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(Original post by Doodlegirl)
Oh dear forgot to put that in duh, see this is what Moks do to you :P. Biology AQA it is hahaha
its alright mocks drive me a little senile too !! Cant believ you'v already done all the textbook Qs and pastpapers:lolwut: haha!

Anyway Im just on photosynthesis now so could you( or anyone else) please distinguish the difference between non-cyclic and cyclic phosphorylartion?

This is what my understanind is so far :
Non-cyclic Phosphorylation (its calld noncyclic because it doesnt recycle electrons..or?)

1)photons from light strike chlorophyll molecule/ photosystem2,thus raising e- (electrons) to higher energy state.

2)E- travel up the Electron Transport Chain (or electron carriers?) , and as they do so they loose energy.this energy is used to create attach Pi +ADP= ATP,via chemiosmosis:THE ATP LEAVES VIA THYLAKOID MEMBRANEs AND ENTERS STROMA FOR LIGHT.Independant REACTION.

*Photolysis of water replenishes the lost e- in photosystem 1, as it creates e-,02, and H+.The h+ are taken up by NADP to form NADP
THIS ALSO GOES TO THE Light.Inependant Reaction.

Now....Cyclic Phosphorylation (its called cyclic because e- are recycled ,but where do these electrons come from? Were they already in photosystem 1,or are they the e- that were used in non-cyclic respiration(photosystem2?
Dno..but here goes:

1)meanwhile at photosystem1, light strikes cholorphyll molecule and excites them, raises them to high e- state and then what? Does NADP come along and get reduced to form NADPH?or... and is any ATP formed?)

I understand non-cyclic i think as its aim is to form ATP and NADPH.but whats the point of Cyclic-Phosphorylation, what does it contribute to the light Indepndant reaction?


Any help would be really appreciated.thanku!

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Doodlegirl
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(Original post by TSRuserrr9)
its alright mocks drive me a little senile too !! Cant believ you'v already done all the textbook Qs and pastpapers:lolwut: haha!

Anyway Im just on photosynthesis now so could you( or anyone else) please distinguish the difference between non-cyclic and cyclic phosphorylartion?

This is what my understanind is so far :
Non-cyclic Phosphorylation (its calld noncyclic because it doesnt recycle electrons..or?)

1)photons from light strike chlorophyll molecule/ photosystem2,thus raising e- (electrons) to higher energy state.

2)E- travel up the Electron Transport Chain (or electron carriers?) , and as they do so they loose energy.this energy is used to create attach Pi +ADP= ATP,via chemiosmosis:THE ATP LEAVES VIA THYLAKOID MEMBRANEs AND ENTERS STROMA FOR LIGHT.Independant REACTION.

*Photolysis of water replenishes the lost e- in photosystem 1, as it creates e-,02, and H+.The h+ are taken up by NADP to form NADP
THIS ALSO GOES TO THE Light.Inependant Reaction.

Now....Cyclic Phosphorylation (its called cyclic because e- are recycled ,but where do these electrons come from? Were they already in photosystem 1,or are they the e- that were used in non-cyclic respiration(photosystem2?
Dno..but here goes:

1)meanwhile at photosystem1, light strikes cholorphyll molecule and excites them, raises them to high e- state and then what? Does NADP come along and get reduced to form NADPH?or... and is any ATP formed?)

I understand non-cyclic i think as its aim is to form ATP and NADPH.but whats the point of Cyclic-Phosphorylation, what does it contribute to the light Indepndant reaction?


Any help would be really appreciated.thanku!

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Hahaha my school is in HK its Asian level to the max here :P
Sure here goes.

Cyclic - Phosphorolation

. The electron flow starts in photosystem I,
. Once the electron is excited by kinetic energy from the sun It travels along the ETC and back to the chlorophyll
. The transport chain (ETC) produces a proton-motive force which pumps H+ ions across the membrane
. This produces a concentration gradient which is used to power ATP synthase during chemiosmosis
. It produces neither O2 or NADPH because (unlike in the non-cyclic) NADP does not accept the electrons they are sent back to the chlorophyll
. the electrons are recycled they are already present in the photosystem.

Noncyclic - Phosphorolation

. This is a two stage process involving both of the photosystems (I and II) the reaction happens on the thylakoid membrane in the chloroplasts
. First a water molecule is broken down into 2H+ + 1/2 O2 + 2e- by Photolysis
. The two electrons produced are kept in photosystem II
. Then a photon is absorbed by chlorophyll pigments which surround the reaction core of the photosystem
. The light excites the electrons within each pigment causing a chain reaction which transfers energy to the core of photosystem II
. This releases the two excited electrons and they are transferred to the primary electron acceptor of the ETC.
. Meanwhile the lost electrons are replaced by the photolysis of another water molecule
. H+ is then pumped into the tylakoid space creating a gradient which provides energy for the regeneration of ATP.
.Since photosystem II replaces its lost electrons from an outside source the electrons that have just been down the ETC which are still excited and transferred to photosystem I Complex, which boosts their energy level to a higher level using a second solar photon.
. The highly excited electrons are transferred to the acceptor molecule.
. The electrons are passed along to a different terminal acceptor and catalyses this reaction NADP
+ + 2H+ + 2e- → NADPH + H+
. This consumes the H+ produced by the splitting of water leading to a net production of
1/2O2, ATP, and NADPH + H
+


it is cyclic phosphorolation that is important to the light independent reaction it is important to create ATP and maintain the amount of NADPH.


Did that help?

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Pinkberry_y
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Make your own ones up


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