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AQA A2 Biology BIOL5 - 17th June 2015

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do we think we'll have to know about pancinian corpuscles? can someone explain it
Original post by shiney101
Isn't pre-mRNA a single strand though? So if the two were to be joined together how are we getting a single strand?

Yes it is, DNA polymerase does the same function as RNA polymerase but with DNA (during DNA replication).
During transcription

DNA double helix --> AATAGT
TTATCA

due to DNA helicase breaking H bonds, separating the helix into two exposed DNA strands.
One of these strands is the coding strand, and free nucleotides form complementary base pairs with this strand
AATAGT (Non-template strand - does nothing for transcription)
AAUAGU(free nucleotides form CBP with template strand) <- Pre mRNA
TTATCA (Template strand)

RNA polymerase joins the AAUAGU together, to form a single stranded molecule (forms sugar-phosphate backbone). This is now the pre mRNA strand.
Original post by hiyaitsnikitaaa
do we think we'll have to know about pancinian corpuscles? can someone explain it


just have an appreciation for the fact that they have stretch mediated sodium channels due to their gellular structure. for example, if you push your hand against a wall the sodium channels in your fingers are distorted and so an action potential is triggered producing the effector of the sensation of 'pressure'.
Original post by hiyaitsnikitaaa
do we think we'll have to know about pancinian corpuscles? can someone explain it




Posted from TSR Mobile

they are receptors, when pressure is applied the sodium-permeable membrane becomes more permeable to sodium ions, influx of sodium ions causes depolarisation of the receptor and triggers a generator potential which is carried as an action potential along the axon.

(this is off the top of my head, apologies for any mistakes)
Original post by Amphoteric
Essentially, yes. Both are forms of gene cloning, i.e. making mass copies of a single gene. Vitro does it by PCR, but vivo does it by bacterial mitosis (binary fission) so you get loads of plasmids with the single gene. With vivo you get the gene already in a vector, so you can use it to produce mass quantities of a particular protein. With PCR you just get lots of identical DNA which you can then use for something like genetic fingerprinting.


Thank you ^_^
Original post by hiyaitsnikitaaa
do we think we'll have to know about pancinian corpuscles? can someone explain it


Mainly how it acts s a receptor by transducing energy (kinetic from pressure to electrical in the impulse)
Its strucutre is basically an unmyelianted neurone end surrounded by lots of lamellae. Each of these lamellae have stretch mediated Na+ channels in them.
At rest (no pressure difference) these Na+ channels are closed as they are too small to allow Na+ to enter. When pressure is applied the lamellae flex, and this causes the Na+ channels to widen allowing an influx of Na+ into the neurone. This causes a generator potential that triggers a localised circuit in the neurone, stimulating depolarisation along the neurone, causing an action potential.
Original post by shiney101
How in depth do we need to know about stem cells/stem cell therapy/bone marrow transplants?


Umm, for stem cells, I think you need to know that stem cells are cells that:
1) divide without external input (and will keep doing so)
2) can develop into any type of cell (undifferentiated)

3 types - totipotent (embryonic stem cells) can give rise to any type of cell and thus can form entire organisms
pluripotent can give rise to any organ system but cannot form an entire organism
multipotent (adult stem cells) can differentiate into any cell type in that tissue e.g. any type of muscle cell.
Specialisation is due to gene expression - certain genes are 'switched on' in certain cells so certain polypeptides are translated
For gene therapy, I think ADA is on the spec but unlikely to ask a big recall question on it, treatment of ADA using retroviruses that you implant into T-cells from the host
Last one isn't on the spec as far as I know, might ask a HSW on it but you'll have all the info there.
Original post by hiyaitsnikitaaa
anyone else feel like theyve not done enough work for this exam? wish there were more past papers on it as ive done the only five there is and its just not enough, i've planned all the essays from these exams and also an extra 5 from teacher predictions, i'm trying to review content but its just becoming more and more difficult
anyone got any revision tips? i've also listened to lots of youtube videos for biol5


Fancy sharing your teacher predictions for the essay? :smile:


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I'm terrified, I have lost all motivation after last week and just not doing anywhere near enough! Someone help? How is everyone revising?:frown:
What are your teacher predictions? :smile:


Original post by hiyaitsnikitaaa
anyone else feel like theyve not done enough work for this exam? wish there were more past papers on it as ive done the only five there is and its just not enough, i've planned all the essays from these exams and also an extra 5 from teacher predictions, i'm trying to review content but its just becoming more and more difficult
anyone got any revision tips? i've also listened to lots of youtube videos for biol5
Should I learn gas exchange/transport eg: in insects/fish from AS for the essay?

Totally forgotten all of that :frown:
Original post by EmilyC96
Fancy sharing your teacher predictions for the essay? :smile:


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proteins, atp, co2, dna technology and ions
these have a few common themes but also lots of breadth
Original post by sn4kebiteheart
What are your teacher predictions? :smile:


proteins, atp, co2, dna technology and ions :smile:
Original post by killmekoalabear
I'm terrified, I have lost all motivation after last week and just not doing anywhere near enough! Someone help? How is everyone revising?:frown:

i feel exactly the same, i finished the past papers a few days ago and no have no idea what to do with my time so im watching youtube videos from mr pollock biology and reading content
Original post by hiyaitsnikitaaa
proteins, atp, co2, dna technology and ions :smile:



an ion essay question would be a dream come true!
Original post by sn4kebiteheart
an ion essay question would be a dream come true!


its been tested before but on the old spec, these are just predictions so i wouldnt just hope for that but it would be nice
Original post by hiyaitsnikitaaa
i feel exactly the same, i finished the past papers a few days ago and no have no idea what to do with my time so im watching youtube videos from mr pollock biology and reading content


I know what you mean, I mean I did a few past papers but I still have more to do.
Feel so overloaded, I have my last 3 exams, all in the space of 30 hours!
Original post by sn4kebiteheart
an ion essay question would be a dream come true!


Any essay on biomolecules would be a dream
Original post by sn4kebiteheart
an ion essay question would be a dream come true!


do you have any 'out of spec' knowledge for ions which you would kindly share? :smile:
Original post by djhodnett
do you have any 'out of spec' knowledge for ions which you would kindly share? :smile:


A good place to start is the kidneys, this is literally a gold mine for homeostasis, osmosis, ions, ATP

Homeostasis : research the renin-angiotensin pathway and ADH

Ions and osmosis - structure and basic function of kidneys is really good (ultraflitration, selective reabsorption of HCO3- Na+ at the proximal convuluted tubule and the ion channels used in this process etc..) and the loop of Henle/collecting duct's role in water retention.

hope it helps :smile:

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