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AQA A2 Biol4 January 2012 pre- exam discussion

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Original post by Erotas
If most of the previous ones have been like that, I can't see why they should choose to change it drastically in January.


Thanks :smile: Just find it ridiculous, I get around 50%-60% in the tests and dont know whether I should be pleased or appalled!
Does anyone have a list or know the pro's and con's of artifical vs natural fertiliser? In the mock I wrote it was cheaper or something along those lines but it wasn't allowed, and I can't seem to find a good list in the textbook or via google.
Reply 242
Original post by Jamsterlavery
Thanks :smile: Just find it ridiculous, I get around 50%-60% in the tests and dont know whether I should be pleased or appalled!



There's plenty of time to improve :tongue: Also I reckon the reason the boundaries are so low is because the exam must be pretty hard and the average across the country must be low. So it's essentially hard to get even 50%. Don't be so hard on yourself :tongue:
i really should start revising! :/
Reply 244
I Haven't revised for it at all. Due to the exam being completely unrelated to the content of BIOL4, I should get an A :smile:
Reply 245
Original post by juliewho
Does anyone have a list or know the pro's and con's of artifical vs natural fertiliser? In the mock I wrote it was cheaper or something along those lines but it wasn't allowed, and I can't seem to find a good list in the textbook or via google.


Artificial:
Contains nitrogen, phosphorus and potassium always - doesn't contain all the nutrients - however with these fertilisers you know the chemical content.
Easy to transport, easy to store, easy to apply.
Nutrients released more easily - these fertilisers are more soluble
Energy required to make them.
Because its more soluble, it can cause leaching, therefore eutrophication.
Can be washed away easily - so more is needed - issues with cost

Organic/ natural
- less energy required to make them - as it's manure etc
- contains a range of nutrients - not just n, p and k.
However too much of a particular nutrient can cause the crop to die
Insoluble - slow release of nutrients
Increases organic content of soil



I know it's loads but these are from my notes which i gathered off previous markschemes , old specs, etc

Hope it helps
Original post by juliewho
Does anyone have a list or know the pro's and con's of artifical vs natural fertiliser? In the mock I wrote it was cheaper or something along those lines but it wasn't allowed, and I can't seem to find a good list in the textbook or via google.


I would put that artificial ones are less smelly, take less time to release the nutrients. etc etc :smile:
Original post by sachinisgod
I would put that artificial ones are less smelly, take less time to release the nutrients. etc etc :smile:


Don't think that particular marking point is on mark schemes :tongue:

Apparently I'm wrong, my bad :redface:
(edited 12 years ago)
Reply 248
Original post by AmbitiousMedic
Don't think that particular marking point is on mark schemes :tongue:


Weirdly, It actually is :s-smilie:
Original post by EffKayy
Artificial:
Contains nitrogen, phosphorus and potassium always - doesn't contain all the nutrients - however with these fertilisers you know the chemical content.
Easy to transport, easy to store, easy to apply.
Nutrients released more easily - these fertilisers are more soluble
Energy required to make them.
Because its more soluble, it can cause leaching, therefore eutrophication.
Can be washed away easily - so more is needed - issues with cost

Organic/ natural
- less energy required to make them - as it's manure etc
- contains a range of nutrients - not just n, p and k.
However too much of a particular nutrient can cause the crop to die
Insoluble - slow release of nutrients
Increases organic content of soil



I know it's loads but these are from my notes which i gathered off previous markschemes , old specs, etc

Hope it helps


Fantastic, thanks a lot. We seem to have raced through this unit and missed out a lot of the smaller details.

Original post by sachinisgod
I would put that artificial ones are less smelly, take less time to release the nutrients. etc etc :smile:


Unfortunately the question was the other way round, the advantages of natural over artificial, but thanks anyway :smile: Adds to my list of pro's/con's!
Original post by craig12
Weirdly, It actually is :s-smilie:


:eek: Okay I'm officially worried about what this exam is going to throw at us...
Reply 251
Original post by AmbitiousMedic
:eek: Okay I'm officially worried about what this exam is going to throw at us...


Well I'm sure 7/8 questions will be totally unrelated to what we have learnt =/ The last question on the paper is usually the one that actually tests your knowledge.
Original post by craig12
Well I'm sure 7/8 questions will be totally unrelated to what we have learnt =/ The last question on the paper is usually the one that actually tests your knowledge.


It's mainly HSW so not much you can actually revise for that, but I think going through past papers and becoming aware of what types of experiments/questions they usually draw upon would be useful. The last ones are the longer ones, I think these shouldn't be too bad because there is only a handful of topics that you can actually spin out for that many marks and so if you're confident with those topics it shouldn't be too much of a problem..
Reply 253
Original post by barzy_j
Is ADP 'used' in the electron transport chain? I did a question we got given and it was one of those respiration experiments about isolating a mitochondria. It basically said the levels of O2 dropped once ADP was added. A mark was for saying ADP is used in the electron transport chain. I can't figure how its used in the chain itself? The only time it comes in is where energy is released from the stalked particles. Anyone?


When electrons are passed down the electron carriers, energy is lost at each stage; this energy is used to combine ADP and Pi to form ATP. Also the chemiosmosis thing (ATP synthase )
Reply 254
Original post by barzy_j
Is ADP 'used' in the electron transport chain? I did a question we got given and it was one of those respiration experiments about isolating a mitochondria. It basically said the levels of O2 dropped once ADP was added. A mark was for saying ADP is used in the electron transport chain. I can't figure how its used in the chain itself? The only time it comes in is where energy is released from the stalked particles. Anyone?


All I can think of is ADP being combined with the inorganic phosphate to produce ATP. This happens as a result of the hydrogen ions diffusing back in to the matrix through ATPase which provides energy for the synthesis of ATP. I guess from there you say, only then can the oxygen combine with those protons (and electrons) to produce water, therefore being used up.
Reply 255
I think there will be lots of respiration in this paper. I really hope so - I just can't cope with shrimps AQA..
Original post by barzy_j
True, see this is what confuses me. The energy released from the carriers is used to pump hydrogen across by active transport right? or just released as heat of course. It's not used to produce ATP is it? The only time I thought that ATP was produced is after the protons diffuse back (chemiosmosis).

And going back to the exam question, shall I just ignore it? ADP isnt used in the electron transport chain really? I stupidly thought it might carry the electrons down it but that just happens in redox reactions.


The pumping and subsequent diffusion of H+ ions is all sort of part of the ETC. The energy released as the electrons pass down the chain is not directly used to combine ADP + Pi but ADP is still used up as a result of this because the energy is used to move H+ ions which then move back again, causing ATP synthase to combine ADP + Pi.

For the purposes of the question, I would consider the whole process, including H+ pumping and diffusion, to be part of the ETC. :smile:
Reply 257
Original post by PatrickD
The pumping and subsequent diffusion of H+ ions is all sort of part of the ETC. The energy released as the electrons pass down the chain is not directly used to combine ADP + Pi but ADP is still used up as a result of this because the energy is used to move H+ ions which then move back again, causing ATP synthase to combine ADP + Pi.

For the purposes of the question, I would consider the whole process, including H+ pumping and diffusion, to be part of the ETC. :smile:


This seems correct :smile:
How are you revising for this? I've pretty much done but still not confident at all :frown:
Stupid HSW :frown:
Reply 258
Original post by barzy_j
True, see this is what confuses me. The energy released from the carriers is used to pump hydrogen across by active transport right? or just released as heat of course. It's not used to produce ATP is it? The only time I thought that ATP was produced is after the protons diffuse back (chemiosmosis).

And going back to the exam question, shall I just ignore it? ADP isnt used in the electron transport chain really? I stupidly thought it might carry the electrons down it but that just happens in redox reactions.


I can see what's confusing you because ADP doesn't directly drive the electron transport chain. But ATP is also produced, like someone has already said above, when electrons release energy as they're passed along the chain.
Reply 259
Original post by PatrickD
The pumping and subsequent diffusion of H+ ions is all sort of part of the ETC. The energy released as the electrons pass down the chain is not directly used to combine ADP + Pi but ADP is still used up as a result of this because the energy is used to move H+ ions which then move back again, causing ATP synthase to combine ADP + Pi.

For the purposes of the question, I would consider the whole process, including H+ pumping and diffusion, to be part of the ETC. :smile:


In my textbook it says that ATP synthesis is also a direct result of the energy released from electrons being passed down the chain. It's like two different things (the pumping of hydrogen ions producing ATP and the energy from electrons producing ATP) happening at the same time :s-smilie:

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