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A2 Biology OCR June 2015 Revision Thread

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Reply 200
Original post by Kell_
Today's my first day of revision so I'm sure you'lll be fine.


Well I can't find that in my he in email textbook - the one with the mri of a brain on the front :/

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Original post by Kell_
I've found something on Page 97 of the Heinemann purple book which I think it wants us to say, but I'm struggling to see how we'd be awarded eight marks for it.

Fatty acid-CoA complex is transported into the mitochondrial matrix where it is broken down into 2-carbon acetyl groups that are attached to CoA. During this breakdowm, by the B-oxidation pathway, reduced NAD and reduced FAD are formed. The acetyl groups are released from the CoA and enter the Krebs Cycle.

Then I'd explain the theory of a general coenzyme.


It wouldn't be eight marks, come on. Heck a speciation question at this level would be 6-8, not this. I can imagine it being 4 marks, and beta oxidation (Don't write B-oxidation, you'll lose marks) is with fatty acids only, probably only worth one or two marks realistically as they don't go into it in our syllabus. You could talk about the link reaction and pyruvate is converted and then say where CoA places acetate next, but I can almost guarantee you that won't be 8 marks, stop it. Also stating NAD and FAD are made is probably an irrelevant point as the question isn't asking about oxphos.
(edited 8 years ago)
Original post by games211
I know what it is but I don't understand how it works :frown:

Its a permanent tube surgically inserted into the abdomen.
Dialysis fluid is pumped into the tube:frown::frown:


The peritoneum is a membrane. It acts as the partially permeable membrane in the Dialysis machine. Urea and excess ions (eg Na+ and K+) will diffuse out because of the concentration gradient, while the glucose levels etc should stay the same.
Original post by AnnekaChan173
The peritoneum is a membrane. It acts as the partially permeable membrane in the Dialysis machine. Urea and excess ions (eg Na+ and K+) will diffuse out because of the concentration gradient, while the glucose levels etc should stay the same.


Thanks

why do this need to happen?
Original post by games211
Thanks

why do this need to happen?


To maintain glucose levels in the body - we don't excrete glucose as it isn't metabolic waste :smile:

So I saw something cute on the AS thread, does anyone want to do a Skype revision session some time? We could run through all of one of the units?
does anyone have last years paper for unit 5? It seems to be non existent online..
Can someone please explain electrophoresis and how the hell it differs from PCR and other methods - this entire topic is a shambles.
Reply 207
Original post by 96akhan
Can someone please explain electrophoresis and how the hell it differs from PCR and other methods - this entire topic is a shambles.



If i do a simple version with a lack of detail for you just to sum up the key points:

PCR- only amplifies (produces many copies) of DNA. They can only be short pieces though. For example DNA found at a crime scene need to be sequenced by there is not enough to do that, so PCR is ran and now we have enough to sequence it.

Electrophoresis - Once some genetic material has been broken up to study (and maybe amplified by PCR if there is not enough to break up and study by its self) then this is used to separate out the fragments of DNA by size. This is because the DNA fragments have a slight negative charge and move towards the positive electrode.

If you want more detail then I'm happy to provide it but that just covers the key ideas/basics of what they do :smile:
May seem odd to ask, but has anyone done the evaluative on woodlice? I've got it after the holidays and it's my last shot at the evaluative! On 30/40 atm, need 36 for an A!!!
Reply 209
Original post by AnnekaChan173
It wouldn't be eight marks, come on. Heck a speciation question at this level would be 6-8, not this. I can imagine it being 4 marks, and beta oxidation (Don't write B-oxidation, you'll lose marks) is with fatty acids only, probably only worth one or two marks realistically as they don't go into it in our syllabus. You could talk about the link reaction and pyruvate is converted and then say where CoA places acetate next, but I can almost guarantee you that won't be 8 marks, stop it. Also stating NAD and FAD are made is probably an irrelevant point as the question isn't asking about oxphos.


It's better to be over-prepared but I somewhat agree it is unlikely that there will be an 8 mark question on it. B was short hand for beta, like it is commonly shorthand for eszett for non-native speakers of German, that don't have the particular key on their keybaord. I assumed people would be able to understand it and the reference to reduced NAD and FAD is a quote from the book, that is party of fatty acids. It was not a separate point, I realise that.

Be a little more gentle next time. I was trying to help.
Original post by Kell_
It's better to be over-prepared but I somewhat agree it is unlikely that there will be an 8 mark question on it. B was short hand for beta, like it is commonly shorthand for eszett for non-native speakers of German, that don't have the particular key on their keybaord. I assumed people would be able to understand it and the reference to reduced NAD and FAD is a quote from the book, that is party of fatty acids. It was not a separate point, I realise that.

Be a little more gentle next time. I was trying to help.


Sorry, wasn't trying to come off rude! The B thing is something I used to do for example. There could be an 6 marker on a larger part of Respiration like oxphos or the use of NAD in respiration/the body, since CoA doesn't really pop up anywhere else, I doubt it.
Reply 211
Original post by AnnekaChan173
Sorry, wasn't trying to come off rude! The B thing is something I used to do for example. There could be an 6 marker on a larger part of Respiration like oxphos or the use of NAD in respiration/the body, since CoA doesn't really pop up anywhere else, I doubt it.


No problem, I was pretty brash too. I'd be up for the Skype revision particularly of F215 because I've missed a lot of it and haven't caught up yet.
Original post by Kell_
No problem, I was pretty brash too. I'd be up for the Skype revision particularly of F215 because I've missed a lot of it and haven't caught up yet.


Same here, we did a lot during the run up to mocks, so I blanked in class when I should have been learning it tbh. Anyone else up for one?
Original post by AnnekaChan173
Same here, we did a lot during the run up to mocks, so I blanked in class when I should have been learning it tbh. Anyone else up for one?


can't we do a youtube live session?
Reply 214
Original post by AnnekaChan173
Same here, we did a lot during the run up to mocks, so I blanked in class when I should have been learning it tbh. Anyone else up for one?


We still haven't finished being taught F215...
Original post by Kell_
We still haven't finished being taught F215...


Same here ;_; just up to Muscle contraction and Half way through biotech. I'm so screwed.


Original post by games211
can't we do a youtube live session?


That involves someone leading it, I don't have the confidence for that hahahahah, with Skype it's a group effort
Original post by AnnekaChan173
Same here ;_; just up to Muscle contraction and Half way through biotech. I'm so screwed.




That involves someone leading it, I don't have the confidence for that hahahahah, with Skype it's a group effort


true :smile: who's up for the skype thing?
I just started doing practice questions and I'm suddenly ****ting myself
I know nothing
Original post by Hmht
If i do a simple version with a lack of detail for you just to sum up the key points:

...

If you want more detail then I'm happy to provide it but that just covers the key ideas/basics of what they do :smile:


Hey
hope ur well :smile:
What do we need to know about primary and accessory pigments?
Original post by AnnekaChan173
I just started doing practice questions and I'm suddenly ****ting myself
I know nothing


That's because, as you said, you haven't finished everything yet :tongue:

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