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lcj0503
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#421
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#421
How Long have people been revising for this exam? I am so stressed about it :-((


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TommehBoi
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#422
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#422
(Original post by lcj0503)
How Long have people been revising for this exam? I am so stressed about it :-((


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Started on Wednesday, would usually start earlier but I have 7 exams this summer (4 done already!) so its hard to focus loads of revision on each exam. What about you?
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Scienceisgood
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#423
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(Original post by TH4RG3)
All you need to know it does is...

ADP + Pi ---> ATP

When the hydrogen ions (protons) diffuse through them when re-entering the matrix.

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Don't forget, it is a reversible reaction!
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v15hu1
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#424
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#424
The importance of the Krebs Cycle [4]


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Scienceisgood
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#425
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(Original post by v15hu1)
The importance of the Krebs Cycle [4]


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The Krebs cycle is used with the conversion of a 2 carbon molecule into a 6 carbon molecule. This then loses 2 carbon dioxide molecules and 2 H atoms to reduce NAD and FAD into NADH and FADH (high energy molecules) which are to be used in the Electron Transport Chain by providing electrons with enough energy to reform ATP from ADP and a Pi ion.
The 4 Carbon molecule is then recycled into the Krebs cycle again.

EDIT: Forgot to say 1 molecule of ATP is produced.

How many marks?
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Scienceisgood
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#426
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#426
8 Mark Question - Describe the process of what goes on during the light independent reaction and how the products of the light dependant reaction are used in it.
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TH4RG3
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#427
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(Original post by Scienceisgood)
Don't forget, it is a reversible reaction!
Obviously yes, but in context to the question, about ATPase/synthase in the ETC, it does that. For the exam you do not need to know anything else about ATPase.

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s24a
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#428
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#428
(Original post by v15hu1)
The importance of the Krebs Cycle [4]


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- its important because it breaks down macromolecules into smaller molecules. e.g = pyruvate ----> co2
- its also important because it produces intermediate compounds that are used in the manufacture of other substances
- krebs also regenerates the 4 carbon molecule that would otherwise accumulate

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TH4RG3
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#429
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(Original post by s24a)
- its important because it breaks down macromolecules into smaller molecules. e.g = pyruvate ----> co2
- its also important because it produces intermediate compounds that are used in the manufacture of other substances
- krebs also regenerates the 4 carbon molecule that would otherwise accumulate

Isnt the first part the link reaction?

Pyruvate + coenzyme A ---> Acetlycoenzyme A + Co2

Then the krebs cycle..

Then the Acetylcoenzyme A binds with the 4 carbon molecule to make a 6 carbon molecule, this is turned back oxidised back into the 4 making Reduced Fad and Nad, important for creating ATP in electon transport chain as they provide the electrons and protons ?

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DELETED ACCOUNT
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#430
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#430
(Original post by Scienceisgood)
The Krebs cycle is used with the conversion of a 2 carbon molecule into a 6 carbon molecule. This then loses 2 carbon dioxide molecules and 2 H atoms to reduce NAD and FAD into NADH and FADH (high energy molecules) which are to be used in the Electron Transport Chain by providing electrons with enough energy to reform ATP from ADP and a Pi ion.
The 4 Carbon molecule is then recycled into the Krebs cycle again.

EDIT: Forgot to say 1 molecule of ATP is produced.

How many marks?
Good. I would just name the compounds really.

actylcoenzyme A
citrate
oxaloacetate

But that's just my opinion. Numbers of carbons can be used instead I think.
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DELETED ACCOUNT
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#431
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#431
(Original post by TH4RG3)
Isnt the first part the link reaction?

Pyruvate + coenzyme A + NAD ---> Acetlycoenzyme A + Co2 + reduced NAD

Then the krebs cycle....

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MLogan
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#432
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(Original post by Scienceisgood)
8 Mark Question - Describe the process of what goes on during the light independent reaction and how the products of the light dependant reaction are used in it.
CO2 binds to RUBP which forms 2 molecules of glycerate-3-phosphate. This is reduced to Triose phosphate using reduced NADP and the energy from ATP which was formed in the Light dependent reaction. The triose phosphate formed can be used to make hexose sugar or it is regenerated into Rubp again so it can bind to another molecule of C02.

Is that 8 marks? I dont think so :|
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s24a
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#433
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(Original post by Scienceisgood)
8 Mark Question - Describe the process of what goes on during the light independent reaction and how the products of the light dependant reaction are used in it.
Light Dependent
-Photosystem 2 absorbs light.
-This excites an electron in the Photosystem 2 and causes it to move higher up in the energy levels.
-The electron passes through an electron carrier and in doing so loses energy.
-The energy lost is used to compine ADP + Pi to make ATP. This process is called photophosphorylation
(-To replace the electrons lost from Photosystem 2, a water molecule undergoes photolysis, to produce electrons. H20 ----->2H+ +1/2 02 + 2e. )
- Photosystem 1, also absorbs light, and this causes an electron to be excited and to move up the engery levels. the increase in energy causes NADP to be reduced.
-Both the ATP and the Reduced NADP are used in the Light Independent Reaction.

Light Independant

- 5 carbon RUBP combines with C02 to make two 3 carbon GP molecules. This reaction is catalysed by the enzyme Rubisco.
- The two GP molecules are then converted into two 3 carbon TP molecules. In order for the conversion to happen, Reduced NADP and ATP are used.
- The TP molecule contributes 1 carbon towards producing a Glucose Molecule.
- The remaining 5 carbons are used to produce the 5 carbon RUBP molecule again. But in order for the conversion to happen an ATP molecule needs to be hydrolysed to provide the energy for the conversion.

Okay after i had done the whole Light Dependent reaction then i had realised that you had asked for the Light Independent Reaction :
so im sorry! But if anyone does read this then please can you point out where i might have put something incorrect. Thanks!
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s24a
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#434
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#434
yeah sorry you are right!
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jonnyb123
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#435
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How is everyone spending their last day revising? I've done all the papers too many times, I'm not sure how much benefit I'll get from going through them again, because I basically know the answers off by heart. (I probably will go through them though)
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jonnyb123
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#436
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(Original post by s24a)
Light Dependent
-Photosystem 2 absorbs light.
-This excites an electron in the Photosystem 2 and causes it to move higher up in the energy levels.
-The electron passes through an electron carrier and in doing so loses energy.
-The energy lost is used to compine ADP + Pi to make ATP. This process is called photophosphorylation
(-To replace the electrons lost from Photosystem 2, a water molecule undergoes photolysis, to produce electrons. H20 ----->2H+ +1/2 02 + 2e. )
- Photosystem 1, also absorbs light, and this causes an electron to be excited and to move up the engery levels. the increase in energy causes NADP to be reduced.
-Both the ATP and the Reduced NADP are used in the Light Independent Reaction.
We don't need to know anything about photosystems. Mark schemes never even mention them
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MLogan
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#437
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(Original post by jonnyb123)
How is everyone spending their last day revising? I've done all the papers too many times, I'm not sure how much benefit I'll get from going through them again, because I basically know the answers off by heart. (I probably will go through them though)
Try and go through as many HSW questions as possible, cause that's what let me down in Jan :|
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TH4RG3
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#438
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#438
(Original post by frogs r everywhere)
Cheers forgot about that!

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s24a
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#439
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(Original post by jonnyb123)
We don't need to know anything about photosystems. Mark schemes never even mention them
okay thanks! its odd though how mark schemes never mention them, as they are in every book i read about Light Independent reaction.
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TH4RG3
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#440
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#440
(Original post by jonnyb123)
We don't need to know anything about photosystems. Mark schemes never even mention them
That is correct, some revsion books seem to have put them in, I think they used to include it (pre 2009) in the papers, however now its not in the Specification or papers

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