AQA A2 Biology BIOL5 - 17th June 2015

I'd definitely say I prefer printing it out and feeling pen on paper. Feels like the real thing.

Me too But thing is, I don't have enough paper or ink for printing a whole load of past papers

Can someone explain why the mark scheme is right for 4a) i) the mark scheme says that over the range labelled A, sodium ions mov out of the axon by diffusion, but everywhere else I've read it says sodium ions move into the axon causing depolarisation. Am I just misinterpreting the question? - thanks

Sodium ions move out when resting potential is being established. Which isn't the case for this graph.
It's showing depolarisation of the membrane so sodium ions are "flooding" into the axon and increasing membrane potential.
Perhaps there is a typo in the mark scheme ?

Yeah I thought, so, thank you!

Does anyone have the unit 5 Jan 2010 and Jan 2011 papers? With mark schemes?
I can't find them on the aqa website.

Hey, is this mutualistic relationship between nitrogen fixing bacteria and plants correct?

Mutualistic relationship between Nitrogen fixing bacteria and plants
-Nitrogen fixing bacteria obtains carbohydrates from plants
-Plants obtain amino acids from Nitrogen fixing bacteria.
(Plants use nitrogen for synthesis of amino acids)


I don't understand how Nitrogen fixing bacteria provides nitrogen for amino acids, I thought nitrogen fixing bacteria converts Nitrogen gas into nitrogen containing compounds?
I thought nitrogen containing compounds need to first be converted to nitrates then taken up by plants to make proteins? or can plants just take up the nitrogen containing compounds from nitrogen fixing and use that to make proteins?

Thanks

I think your looking into it too much. All you have to know is nitrogen is either fixed into the soil by free living bacteria to ammonia then oxidised to nitrite then nitrate, or the nitrogen is fixed directly into the plant by mutualistic bacteria.
You don't really need to know how the nitrogen from mutualistic bacteria ends up as nitrate.
You then need to know that the nitrates from soil are used to make amino acids, RNA, DNA and ATP for growth.

lol thats cause that werent any xD
unit 5 only have exams for june

I think your looking into it too much. All you have to know is nitrogen is either fixed into the soil by free living bacteria to ammonia then oxidised to nitrite then nitrate, or the nitrogen is fixed directly into the plant by mutualistic bacteria.
You don't really need to know how the nitrogen from mutualistic bacteria ends up as nitrate.
You then need to know that the nitrates from soil are used to make amino acids, RNA, DNA and ATP for growth.

What things can I revise to get the out of spec marks for the past essay questions or do the markschemes tell you this if I look at them?

Can someone please explain question 3b) for me please?
http://filestore.aqa.org.uk/subjects/AQA-BIOL5-QP-JUN14.PDF

I'm confused about probability and chance... Can someone explain it to me?
Thanks

does anyone have any good youtube tutorials/lessons for unit 4 or 5?

loved the mygcsescience ones for gcse so I'd be v grateful if anyone has any similar a2 recommendations

I never really get those questions either but I think they're basically talking about statistical tests and whether the result is significant to 95%. So for the marks I think you would say 1) the difference is significant 2) because the probability of the results being due to chance is less than 5%. With chance they mean it is entirely random and not due to a scientific reason