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Edexcel A2 Biology Unit 5 (6BIO5) - 22/06/2011- OFFICIAL THREAD !

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Can anyone please summarise what phytokines do and all that Pr and Pfr stuff - its just too confusing... PLEASE

Phytochromes are the photoreceptors in leaves, stem, root and shoot of plants.

Pr is converted to Pfr in daylight, and Pfr is converted to Pr in night time.

They control the flowering of plants (and germination of some). 'Long Day' plants will flower with a lot of Pfr as there is not much darkness so not much Pfr is converted back to Pr. 'Short Day' plants will flower with lots of Pr as there is enough darkness to convert the Pfr back to Pr.

This means plants can flower in different seasons depending on the day length.

There is also the fact that Pfr is changed back to Pr in far-red light, but that is unlikely to come up.

(edited 12 years ago)

Reply 2541

xshopoholicx

Original post by Hibz93

In the article it says "viruses are recognized and destroyed by the immune system".
How does that happen? In one of the notes here it says that blymphocytes produces antibodies that destroys it. But doesn't antibodies only destroy bacteria, or can it also destroy viruses?

t killer cells causes the infected cell to lyse
also the antibodies stop toxins reaching human cells
and it binds to the capsid coat in clumps for the macrophages to easily recognise the clump and engulf it

Reply 2542

abuelzouz

hey guys.. how do we calculate heart rate from an ECG? i suck ath that!!! there is a que in specimen paper like that :smile:

thnx in advance

Reply 2543

lbavfc

Could someone please explain to me what we might need to know about stem cells?

Reply 2544

gildartz

Original post by Hibz93

B lymphocytes can recognise the viral antigens and become APCs themselves. The T-helper cells can then bind to the B cell APC and cause it to divide into B memory and B effector cells which differentiate into plasma cells which produce the antibodies. The anti-bodies can label the viruses which are still in the blood and allow the macrophages to engulf them. The viruses which have already infected the somatic cells can be destroyed by the T-killer cells.

Someone correct me if I'm wrong though, my memory is a bit fuzzy.

Original post by Kayak

I'm too slow- get rather caught up in my game/book! And even when I do, by strange coincidence, a text will go off, so I will be accused of texting and not revising!

Lol, practise makes perfect. I've done it so many times that it's turned into a reflex :tongue:

Reply 2545

Meesta

i am sorry to ask guys, but does anyone have a link to the specimen paper and / or MS? i can't seem to find it anywhere!

Reply 2546

gildartz

Original post by abuelzouz

hey guys.. how do we calculate heart rate from an ECG? i suck ath that!!! there is a que in specimen paper like that :smile:

thnx in advance

They should have time along the bottom. See how long it takes to get from one R wave to the next, that'll tell you how long each beat takes, then turn that into beats per minute.

Reply 2547

abuelzouz

Original post by Meesta

i am sorry to ask guys, but does anyone have a link to the specimen paper and / or MS? i can't seem to find it anywhere!

here u go ... all here

http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/sam-gce-biology.pdf

gd luck

Reply 2548

knowledgeISgood

oh god, im going to flop this for sure...... i know nothing....

Reply 2549

Meesta

Original post by abuelzouz

here u go ... all here

http://www.edexcel.com/migrationdocuments/GCE%20New%20GCE/sam-gce-biology.pdf

gd luck

ahhh thanks :biggrin:

Reply 2550

Rizam

Original post by sheep_go_baa

You live in Kuwait?? So you're doing this syllabus from there?! wow

yeaaah .. :P
Cant see why that was shocking :biggrin:

Reply 2551

abuelzouz

Original post by gildartz

They should have time along the bottom. See how long it takes to get from one R wave to the next, that'll tell you how long each beat takes, then turn that into beats per minute.

thnx for replying bro..
under graph it says 1 second.. (10 small blocks) and between each R wave there are 10 blocks also... 3 R waves... wts next?

Reply 2552

Adam9

Some people have suggested to do the last, 30 mark pre-release based question first.
I don't even think that will have any benefit, is anyone here going to do that, and why?

Reply 2553

StudentToday

List five distinctive effects of light on plant growth. (5)

any ideas..? Not reli sure how to answer this

Thanks, Charli :smile:

Reply 2554

sheep_go_baa

Wait, how come the June 2010 paper was 1h 30mins, but the Jan 2011 paper is 1h 45mins...are they not both out of 90???

Reply 2555

gildartz

Original post by abuelzouz

thnx for replying bro..
under graph it says 1 second.. (10 small blocks) and between each R wave there are 10 blocks also... 3 R waves... wts next?

So 10 blocks correspond to 1 second? If so then the heart rate would be 60 bpm since each beat lasts for a second

Reply 2556

billybo_h

Original post by sheep_go_baa

Wait, how come the June 2010 paper was 1h 30mins, but the Jan 2011 paper is 1h 45mins...are they not both out of 90???

In the examiner report it mentions that they found people struggled due to the time limitations, so they extended it. People couldn't finish all the pre-release questions apparently.

Reply 2557

Meesta

Original post by Adam9

Some people have suggested to do the last, 30 mark pre-release based question first.
I don't even think that will have any benefit, is anyone here going to do that, and why?

prob to get the heart breaking questions out of the way!!! but i'm just going to do from 1-7.

Reply 2558

sheep_go_baa

Original post by billybo_h

In the examiner report it mentions that they found people struggled due to the time limitations, so they extended it. People couldn't finish all the pre-release questions apparently.