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A2 Biology OCR June 2015 Revision Thread

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F214 is more interesting than f215!! :smile:
Original post by bburn96
Hello guys

How are your preparations for #f214
I am worried about it
Can someone explain what substrate level phosphorylation means ?

Thanks in advance .... cheeers !

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Substrate-level phosphorylation refers to the production of ATP from ADP + inorganic phosphate. For example, during glycolysis, the krebs cycle and oxidative phosphorylation :smile:
Original post by domcandrews
F215 - if we were asked "outline the steps involved in sequencing the genome of an organism" - would you talk about genome mapping, BAC's and then how to sequence a BAC section? What kind of detail would we need to add in to answer this question? Possible 8 or 9 marker, so just wondering. cheers x


1) Chain termination method to create different DNA fragments.

2) Inserting different fragments into separate BAC's.

3) Allow the BAC's to divide to create colonies. This creates a genomic DNA library.

4) Extracting fragments from the BAC colonies.

5) Cutting fragments with the same restriction enzymes to create overlapping DNA fragments.

6) Sequence the fragments in the BAC colonies. (Using DNA ligase).

7) Combine all the DNA fragments from each BAC using the same method in 6) to sequence a full genome.

This was off the top of my head, so some steps may be missing/wrong haha :smile:
Original post by Lighfy
1) Chain termination method to create different DNA fragments.

2) Inserting different fragments into separate BAC's.

3) Allow the BAC's to divide to create colonies. This creates a genomic DNA library.

4) Extracting fragments from the BAC colonies.

5) Cutting fragments with the same restriction enzymes to create overlapping DNA fragments.

6) Sequence the fragments in the BAC colonies. (Using DNA ligase).

7) Combine all the DNA fragments from each BAC using the same method in 6) to sequence a full genome.

This was off the top of my head, so some steps may be missing/wrong haha :smile:


Thank you for this! Was just a bit confused as the textbook sets it out in a weird way. Just another question when would all the annealing/dna polymerase adding free nucleotides occur in this sequence or would i not include that? Just can't get my head around it atm!
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can someone please explain to me how you would know what different wavelengths of light are absorbed/reflected if they give you a question in terms of different coloured filters etc? Thank you!
Original post by domcandrews
Thank you for this! Was just a bit confused as the textbook sets it out in a weird way. Just another question when would all the annealing/dna polymerase adding free nucleotides occur in this sequence or would i not include that? Just can't get my head around it atm!


You're talking about polymerase chain reactions there.

In sequencing, after you get your bacteria DNA that collectively contain the entire genome, you sequence it out via interrupted PCR with termination nucleotides

I think the bit about DNA ligase is wrong because even if you do combine the bacterial DNA together to get the full genome, you just end up with the genome you first started with. Because you can't generally can't sequence DNA that's the entire genome length (termination nucleotides prevent this), you sequence the bacteria DNA fragments you extract off them, as they're shorter.

So after you get a lot of sequences that each add up to the whole genome, you see where there's overlap, which should give you the order of your base pairs

That was awfully explained. If anyone wants to do it better, go ahead
Original post by bburn96
Hello guys

How are your preparations for #f214
I am worried about it
Can someone explain what substrate level phosphorylation means ?

Thanks in advance .... cheeers !

Posted from TSR Mobile


Hey, think of it this way:

Phosphorylation literally means the addition of a phosphate group, so like with ATP from adp and pi
Original post by BioAgent
how is everyone revising? Are you guys just concentrating on f214 now?


yes until monday and then f215 all the way
Original post by domcandrews
Thank you for this! Was just a bit confused as the textbook sets it out in a weird way. Just another question when would all the annealing/dna polymerase adding free nucleotides occur in this sequence or would i not include that? Just can't get my head around it atm!


What ChoccyPhilly said best describes this. My explanation was pretty rubbish, sorry about that :biggrin: It is a pretty confusing technique, think I may need to look over it again.
Original post by ChoccyPhilly

Wow, you seemed better prepared than most of us in this thread. I don't know how you're spreading yourself for the other subjects but if you allocate maybe 2-4 hours a day solely on unit 5, you could very well set yourself up for a good grade in a fortnight


Original post by maisie__x
You're not screwed! In my opinion whilst F215 is boring and there's a lot to learn, it's a lot easier and some of the topics, like animal/plant responses, are really small and quick to learn. Obviously the best grades come from doing past papers and learning absolutely everything, but I still think you can get a decent enough grade on F215 by skimming over some things. Some of the questions on past papers seem like common sense, advantages and disadvantages of things :smile:

(that being said look over the ecosystems topic if nothing else, there's always loads on that)


LOOOOOOL oh God you thought I was prepared :') my unit 5 knowledge flew out of the window with my maths retakes and S2 revision. Maybe 2-4 from Saturday or Sunday or after unit 4, but I guess I'll start looking at it! Thank you :smile:
Original post by tewas
can someone please explain to me how you would know what different wavelengths of light are absorbed/reflected if they give you a question in terms of different coloured filters etc? Thank you!


If you had a green filter, then only green wavelengths of light would be able to pass through. Other wavelengths of light, such as blue and red, are reflected.
Original post by tewas
can someone please explain to me how you would know what different wavelengths of light are absorbed/reflected if they give you a question in terms of different coloured filters etc? Thank you!


One of the packs on physicsandmathstutor has a photosynthesis Q like this. Think of the colours in the plant. Chlorophyll a/The plant itself best absorbs red light, but is green. So if a red filter is placed, it will absorb more light, more photolysis etcetc, it will photosynthesise more. If a green filter is placed, that light will be reflected and won't be used in photosynthesis. Don't say that photosynthesis doesn't happen, however - there are still accessory pigments like Xanthophyll and Carotene that can absorb different wavelengths of light and pass the energy down to the primary pigment centre. Hope that helps any?
Original post by Lighfy
If you had a green filter, then only green wavelengths of light would be able to pass through. Other wavelengths of light, such as blue and red, are reflected.


You are correct in saying only green wavelengths pass through. However other wavelengths are absorbed by the filter. If they were reflected we would see those colours. Opaque objects reflect (and absorb) and we see colours that are reflected. Transparent objects let light through them (which we see) and absorb other colours.

PS I thought the same as you at first and thought other colours are reflected. But then it occurred to me if they are reflected we would see those colours. So I looked it up and that's what I found.😊

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(edited 8 years ago)
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Original post by AnnekaChan173
One of the packs on physicsandmathstutor has a photosynthesis Q like this. Think of the colours in the plant. Chlorophyll a/The plant itself best absorbs red light, but is green. So if a red filter is placed, it will absorb more light, more photolysis etcetc, it will photosynthesise more. If a green filter is placed, that light will be reflected and won't be used in photosynthesis. Don't say that photosynthesis doesn't happen, however - there are still accessory pigments like Xanthophyll and Carotene that can absorb different wavelengths of light and pass the energy down to the primary pigment centre. Hope that helps any?


yes! thank you that helps so much! yes i saw a question about the NaHCO3 solution changing due to different filters with increasing and decreasing pH and that's what confused me :frown:so are you only expected to know that:
- chlorophyll a absorbs red light, reflects green
- chlorophyll a can also absorb blue light
- chlorophyll b appears blue-green in colour
- carotene and xanthophyll absorb blue light and reflect yellow-orange?
also, sometimes in mark schemes they talk about short/long wavelengths absorbed/reflected - how are we meant to know this? are we supposed to know the wavelengths?
Wow just came across this question:

"Describe the advantages to animals of innate and learned behaviour with reference to specific examples of each type of behaviour" (11)

Guess I'll be basicaly memorising the mark scheme for that one
Hi guys. I was just wondering what we need to know for the kidney methods except for kidney transplant like the dialysis etc? Which methods and what detail?
Also f215 what synoptic stuff do we need to know?
Thank you
Original post by Hilton184
Spec says we only have to 'evaluate' evidence for chemiosmosis so I don't think we have to recall it, I wouldn't bother learning it.

But something along the lines of...

pH of inter membrane space much lower than pH of matrix.
Disrupting ATP synthase enzyme prevents production of ATP, but electron transport chain still occurs.


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Usually They come up in tix boxes but how the hell do we know what to tick??? I get really confused with Q like that
Original post by ChoccyPhilly
Wow just came across this question:

"Describe the advantages to animals of innate and learned behaviour with reference to specific examples of each type of behaviour" (11)

Guess I'll be basicaly memorising the mark scheme for that one


Question paper?
Original post by TheLegalDealer
Question paper?


June 2011. I'm doing it now and this entire paper is just awful
Original post by AnnekaChan173
One of the packs on physicsandmathstutor has a photosynthesis Q like this. Think of the colours in the plant. Chlorophyll a/The plant itself best absorbs red light, but is green. So if a red filter is placed, it will absorb more light, more photolysis etcetc, it will photosynthesise more. If a green filter is placed, that light will be reflected and won't be used in photosynthesis. Don't say that photosynthesis doesn't happen, however - there are still accessory pigments like Xanthophyll and Carotene that can absorb different wavelengths of light and pass the energy down to the primary pigment centre. Hope that helps any?


Is that all you need to know regarding wavelntgjd pigments and accessory pigments?

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