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AQA Biology A2 Unit 4: Populations and Environment - 16th June 2016

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Original post by kkboyk
It's ok :tongue: What would you say would be your biggest weakness in unit 4? For me it has to be the questions involving us to interpret a particular graph/table, and infer what its showing.

I always thought that Psychology has twice as much info than Biology. I'm so glad I've dropped all essay based subject purely because I can never finish a bunch of essays in time, plus the content is too much for me (+_+).


I would probably say that too- I have always hated graph analysis😂 I also find if the 5 markers at the back are obscure (i.e. about ATP instead of directly about photosynthesis or respiration) I fall down.

I think Biology has more content this year, especially with unit 5. Psychology you can get away with generalizing things I find, but biology is so so picky with certain things like wording!!

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Reply 62
Original post by KatieAlicexxx
I would probably say that too- I have always hated graph analysis😂 I also find if the 5 markers at the back are obscure (i.e. about ATP instead of directly about photosynthesis or respiration) I fall down.

I think Biology has more content this year, especially with unit 5. Psychology you can get away with generalizing things I find, but biology is so so picky with certain things like wording!!

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I usually never bother trying with the last question because of that (except the part of the question which are worth 1 marks). If I'm feeling very desperate then I usually just write a bunch of key words (i.e if it's talking about the cholorphyll, I just randomly write light pigment or something) to gain at least 1 mark on a question.

Yeah it does, and it scared and demotivated me :frown: Compared to AS, A2 is like a big bully hanging you upside down. Other exam boards are a bit better in terms of pickiness like Edexcel.
Reply 63


Is that from your notes? I say its good but confused with R- word like RNADP, RFAD
Im not sure if im allowed to edit because you can cross out words
Original post by Ordo
Is that from your notes? I say its good but confused with R- word like RNADP, RFAD
Im not sure if im allowed to edit because you can cross out words


its just how I rememeber it lol

reduced NAP
Reply 65
Original post by Proxenus
its just how I rememeber it lol

reduced NAP


Ooh I didnt realise that was so obvious XD
Original post by cherrybanana
Picture6.pngCan anyone please explain how this answer (in red) was achieved? :smile:


What was the direct question? The picture doesn't show it :smile:
Original post by charlie2466
What was the direct question? The picture doesn't show it :smile:


The question is the part in bold black where it says "calculate the percentage reduction..." :smile:
What's the difference between ATPase and ATPsynthase and what are their roles in the ETC?
Do we need to learn about Chi-squared tests and Spearman's Rank or was that just for the ISA?
Original post by cherrybanana
Picture6.pngCan anyone please explain how this answer (in red) was achieved? :smile:


So ...
You find out the total seed production in the fenced area and unfenced area --> fenced is 263 x 36.7 = 9652 and unfenced is 50 x 25.8 = 1290.
Now you know the total seed production you calculate the percentage decrease in the seed production from the fenced to the unfenced area (as in the unfenced area is where sheets can graze)
So the formula for percentage decrease is (original number - new number divided by original number x 100) this would give you 9652 - 1290 divided by 9652 x 100 = 87%
Original post by charlie2466
So ...
You find out the total seed production in the fenced area and unfenced area --> fenced is 263 x 36.7 = 9652 and unfenced is 50 x 25.8 = 1290.
Now you know the total seed production you calculate the percentage decrease in the seed production from the fenced to the unfenced area (as in the unfenced area is where sheets can graze)
So the formula for percentage decrease is (original number - new number divided by original number x 100) this would give you 9652 - 1290 divided by 9652 x 100 = 87%


Thanks so much!!!!! I totally get it now! Your explanation was really clear :smile:
Does anyone know if we can bulletpoint for this exam? Or not write in full sentences
Yeah my teacher said your allowed to bullet point as it makes it more clear for the examiner.
jk.pngHow do you achieve this answer? (in red)
k.pngAlso, can anyone please explain this answer (in red)?
Original post by cherrybanana
jk.pngHow do you achieve this answer? (in red)


Hope this helps :smile: image.jpg
Reply 77
Original post by cherrybanana
What's the difference between ATPase and ATPsynthase and what are their roles in the ETC?


DO not use ATPase! This is for the muscles! ATPase hydrolyses the ATP into ADP + Inorganic phosphate, to allow the myosin head to 'recock'.

ATPsynthase is used in either oxidative phosphorylation (Elec transport chain in respiration)
Or- The light dependent reaction in photosynthesis

- In ETC the energy lost from the excited electrons going down the electron carriers is used to transport hydrogen atoms from the mitochondrial matrix into the intermebrane space, this then creates an electrochemical gradient and there is now a higher conc of hyrogen atoms in the intermembrane space so the H atoms down their conc gradient via the enzyme ATPsynthase, which drives the process of combining ADP + Inorganic Phosphate to form ATP :smile:
Original post by charlie2466
Hope this helps :smile: image.jpg


Thanks so much! :smile:

I just wanted to ask:
how did you find the value 16mm... is that the height of the muscle fibre (measured vertically) or is it the width of on sarcomere (measured horizontally). Because wouldn't it have to be the height as this is the diameter?

Also, why would you divide the magnification by the value that you measured (height/width)? Is this linked to the equation from AS which is Image = Magnification x Actual size?
Original post by K3001N
DO not use ATPase! This is for the muscles! ATPase hydrolyses the ATP into ADP + Inorganic phosphate, to allow the myosin head to 'recock'.

ATPsynthase is used in either oxidative phosphorylation (Elec transport chain in respiration)
Or- The light dependent reaction in photosynthesis

- In ETC the energy lost from the excited electrons going down the electron carriers is used to transport hydrogen atoms from the mitochondrial matrix into the intermebrane space, this then creates an electrochemical gradient and there is now a higher conc of hyrogen atoms in the intermembrane space so the H atoms down their conc gradient via the enzyme ATPsynthase, which drives the process of combining ADP + Inorganic Phosphate to form ATP :smile:


Ohhhh!!! I totally understand it now! :smile: :smile: :smile: Thanks so much!!!

Can you pleaseeee explain the process of muscle contraction (sliding filament mechanism) with reference to ATP and ADP + Pi? I get really confused as to when each is used? And also the words "recocking" and "power stroke" ! Pleaseee! :smile:

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