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AQA A2 Biology BIOL5 - 17th June 2015

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Original post by Bustamove
LOL, I just re read my post and I realised I made a typo... I was suppose to say "shaded side of shoot", not "shaded side of root"
Sorry... :tongue:

Stages of tropism
-Cells in the top of shoot produces IAA
-Light causes IAA to move from light side to shaded side of shoot
-Higher concentration of IAA on shaded side
-Shaded side of shoot elongate more?
-Causes shoot to bend towards light


so is this correct? sorry about the typo
thanks :smile:


Yep, that's correct I believe :smile:
Reply 161
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Hudl
16
Are parasympathetic and sympathetic nerves autonomic nerves only or are these nerves also present in voluntary responses?
Hey guys. This is off topic but if anyone needs help in Physics/Chem task 3 (a2), feel free to PM me :smile:
Reply 163
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Hudl
16
Original post by Bustamove
Also, is this correct? (sorry if I am spamming the page)


How Resting Potential is achieved
-Sodium potassium pump actively transports 3Na+ out and 2K+ into axon
-Creates chemical gradient, more positive outside axon. The axon is said to be polarised
-Sodium ion channel is closed, potassium ion channel is open.
-K+ diffuses out of the axon
-Build up of positive ions outside the axon
-equilibrium established, the resting potential is at -65mV


Action Potential
Stimulus stage
-A stimulus causes voltage gated Na+ channels to open

Depolarisation stage
-Na+ diffuses into axon down electrochemical gradient
-Large influx of Na+ ions causes membrane to depolarise
- Na+ ions diffusing into the axon causes more Na+ ions to diffuse into the axon (Positive feedback)
-Action Potential is created when depolarisation up to +40mv is achieved

Repolarisation stage
-At +40mv, voltage gated K+ is open, Na+ channel close
-K+ diffuses out of axon
-Outward diffusion of K+ causes membrane to hyperpolarise

Hyperpolarisation stage
-Hyperpolarisation causes voltage-gated K+ channels to close

Resting potential stage
-Sodium-potassium pump moves 3Na+ out and 2K+ into the axon
-Resting potential re-established.


Original post by Bustamove
LOL, I just re read my post and I realised I made a typo... I was suppose to say "shaded side of shoot", not "shaded side of root"
Sorry... :tongue:

Stages of tropism
-Cells at the tip of shoot produces IAA
- Initially IAA is transported to all sides
-Light causes IAA to move from light side to shaded side of shoot
-Higher concentration of IAA on shaded side
- This causes elongation of cells on the shaded side
- The shaded side grows faster causing the shoot to bend towards the light


NOTE: In geotropism, the high conc of IAA decreases growth in root cells.


so is this correct? sorry about the typo
thanks :smile:


This is how I would word it, you have the general idea though and what you wrote will probably get the marks aswell.
(edited 8 years ago)
Original post by Hudl
This is how I would word it, you have the general idea though and what you wrote will probably get the marks aswell.


wait, so only in geotropism, IAA causes decrease in growth of root cells?
but in tropism, IAA causes cells to be more elongated?
Reply 165
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Hudl
16
Original post by Bustamove
wait, so only in geotropism, IAA causes decrease in growth of root cells?
but in tropism, IAA causes cells to be more elongated?


Yes just be aware when AQA ask questions to do with root cells that IAA has the opposite effect as it does to the stem, causing a decrease in growth of root cells.
Original post by Hudl
Yes just be aware when AQA ask questions to do with root cells that IAA has the opposite effect as it does to the stem, causing a decrease in growth of root cells.


thanks :smile:
Does anyone have any good ways to remember some of the stages for bio5? For example for producing DNA fragments, does anyone have a easy way to remember the order for isolation,insertion,transformation etc?
Hey guys. I have done Chem task 3. Just making a statement thats all. If by any chance people have done Bio task 3..I would not mind helping you revise for the Chem...
Reply 169
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Hudl
16
In the Menstrual cycle when there is postive feedback after the initial inhibition of FSH & LH. At the crtical point there is a surge in the production of FSH why is this? Why would yo want the follicles to develop further when the LH is gonna cause ovulation anyway?
Original post by ~amethyst~
Does anyone have any good ways to remember some of the stages for bio5? For example for producing DNA fragments, does anyone have a easy way to remember the order for isolation,insertion,transformation etc?


Have you done the practical? If not, try to go search some youtube videos and have a look at them, try and imagine logically what you will do each step, then it is easier to remember.
Original post by Hudl
In the Menstrual cycle when there is postive feedback after the initial inhibition of FSH & LH. At the crtical point there is a surge in the production of FSH why is this? Why would yo want the follicles to develop further when the LH is gonna cause ovulation anyway?


A very good question.. TBH, i don't really know, the textbook and my teacher dont seem to cover that detail... i would think when oestrogen increases and passes the threshold level, FSH is stimulated as well.... but not to a great extent because you don't want another follicle to mature...
Here is a detail website on menstrual cycle which could be helpful:

http://www.passmyexams.co.uk/GCSE/biology/menstrual-cycle-and-hormones.html
Original post by Bustamove
hey guys, genetic fingerprinting is really stressing me out! I have 2 books which seems to tell me two different things?
One of them includes southern blotting, but do we really need to know about it? I can't seem to find it in the spec

Is this what genetic fingerprinting is? (sorry, I'm learning it all on my own with no teacher)


Stages of genetic fingerprinting
- Sample of DNA extracted and put in PCR
-PCR makes copies of areas of DNA containing repeated sequences
-Fluorescent tag is added to all DNA fragments
-DNA fragments undergo electrophoresis
-Fragments are seperated according to size
-DNA fragments are viewd as bands under UV light


This is what my CGP says, but then again, I've got the old version and sometimes the CGP book can be unreliable...please can someone tell me if this is correct?
Thanks :smile:


Hey, the way I've been taught genetic fingerprinting is as follows:

- Extract DNA
- Create DNA fragments using restriction enzymes
- Separate fragments using gel electrophoresis
- Soak in alkali to separate double stranded DNA into single stands
- Transfer to nylon membrane via Southern Blotting
- Hybridisation - introduce DNA fragments specific to certain sequences, with fluorescent labels
- Cover with X-Ray sheet and expose. This produces an x-Ray image as the DNA fragments with the fluorescent markers attached light up.

I think that CGP book gives a general overview of electrophoresis. Also as far as I know we have to know southern blotting exists but don't have to know specifics but that could be wrong.

We did the practical at school but my teacher let the gels run over night so all our fragments ran over the edge of the gel haaaa

Hope this helps :smile:
Does anyone else feel ready to take the exam and basically sitting around for a month waiting for it to happen haha?
Original post by ali_blue
Does anyone else feel ready to take the exam and basically sitting around for a month waiting for it to happen haha?


I'm almost at this point...disadvantage of studying since September!:')
Reply 174
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Hudl
16
I was just wondering, if you decide to resit your EMPA for AQA do you keep your highest grade?
Original post by MollyMcFly1
I'm almost at this point...disadvantage of studying since September!:')

I know right! And there's only 5 past papers you can do....... Ahhh!
Original post by ali_blue
I know right! And there's only 5 past papers you can do....... Ahhh!


I know:frown: I've just been doing loads of the really old questions from exampro...
Original post by Hudl
I was just wondering, if you decide to resit your EMPA for AQA do you keep your highest grade?


Yeah u do :smile:


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Reply 178
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Hudl
16
Original post by Ruby_1696

Are you sure of this? my teacher was saying you will keep the grade you get the second time round better or worst
nvm
(edited 8 years ago)

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