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AQA BIOL5 ~ 17th June 2013 ~ A2 Biology

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What do people think may come up in the essays?. hard to predict with only 3 past papers as there is still a lot they haven't covered but yeah, what do you think? ?????

Reply 3281

Lyont

Original post by ecokid

I need 50ums more for my overall B grade. I have the grades from all the other modules.So anyone guess roughly how many marks 50ums is likely to be?

50 ums was an E grade last year.

Source: http://store.aqa.org.uk/over/stat_pdf/UMS-GRADE-BOUNDARIES.PDF

Reply 3282

hollywils

Original post by benharris94

What do people think may come up in the essays?. hard to predict with only 3 past papers as there is still a lot they haven't covered but yeah, what do you think? ?????

ATP I reckon or cell functions!

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Reply 3283

krane

Original post by currydud

not all hormones are, testosterone is a hormone but not a protein :smile:

Original post by James A

Not all are.

Adrenaline isn't a protein. It's a carbohydrate.

Cheeeeers

Reply 3284

kingpro88

Any ideas on what the essay might be ?

Reply 3285

Starlight94

I'm a bit confused with gel electrophoreisis, I understand the further the fragments move, the smaller they but i'm a but confused about the terminator base thing, is is related to this or completely different?

Reply 3286

Lyont

Original post by kingpro88

Any ideas on what the essay might be ?

I suspect it will be on ATP, however it is hard to know as there has been sop few papers /: But i've found the best way to revise for the essay at this stage is to learn the synoptic cycles from unit 4 etc as they tend to be applicable to most questions in some way or another :smile:

Reply 3287

krane

Can anyone tell me how the oestrous cycle could be an example of both negative and positive feedback? :smile:

Reply 3288

YWArtist

Original post by bad8oy

Complementary T cells bind to antigen expressed on phagocyte
Stimulates the division of T cells by mitosis. Develope to form memory cells and cytotoxic T cells that produce a toxin that make holes in membrane of pathogen.
Also divide into T helper cells.

B cells then take up antigen of pathogen and express it on surface
T helper cell binds to it activating the B cells which now divide by mitosis to form memory B cells and plasma B cells.
Plasma cells produce Y shaped antibodies and complementary to antigen and form antigen antibody complexes.

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Where is this? :s its nowhere in the cgp revision guide

Reply 3289

Lyont

Original post by Starlight94

I struggle with gel electrophoresis too, what i find difficult is understanding the difference in restriction mapping and DNA sequencing. I assume the terminator base is the base that stops the DNA sequence, similarly to a stop code?

Reply 3290

DELETED ACCOUNT

Original post by YWArtist

Where is this? :s its nowhere in the cgp revision guide

Its Unit 1 knowledge (Nelson thornes)

Reply 3291

tn234

Original post by LegendX

Hi guys, here is an essay of which, by an examiners standards would easily score full marks.

are there any more examples? :smile:

Reply 3292

Anjna

Original post by krane

Can anyone tell me how the oestrous cycle could be an example of both negative and positive feedback? :smile:

negative feedback: when small amounts of oestrogen is beiung released by fsh, the uterus lining begins to build up and so inhibits the release of fsh (and lh) from glands

positive feedback: oestrogen stimulates gland to release LH and FSH which further stimulates the ovaries to release oestrogen

negative feedback: LH stimulates the corpus luteum to develop which produces progesterone. progesterone inhibits further release of LH

Reply 3293

Lyont

Original post by krane

Can anyone tell me how the oestrous cycle could be an example of both negative and positive feedback? :smile:

FSH stimulates the creation of new follicle, new follicle secretes oestrogen, low levels of oestrogen then inhibit FSH and LH (negative feedback)

As the follicle grows more, by around day 10 higher levels of oestrogen is produced, this causes the inhibition to be reversed, so now oestrogen stimulates FSH and LH (positive feedback)

Later on, after ovulation the corpus leutum (formed by LH) secretes progesterone, progesterone inhibits FSH and LH (negative feedback)