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Edexcel GCE Biology Unit 5 6BI05 June 2013

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Reply 1040
Avatar for Sly1
Sly1
6
Original post by hussaincute
the things u have mentioned are the basics for me for any paper i do... but wat seems not to be working for me is that whenever i see the markscheme the content is completely different from wat i have learnt frm books ... watever i write in exams perfectly makes sense to the question but the mark scheme has some of the answers which r not even related to the questions ... this gets me confused every time

Understand each command words, like describe, suggest,...
i hope that u wud have done june 2012 paper so if u go to Q2 (b) and (c) n explain how wud u actually link that to ur basic knowledge? ur help will be appreciated
Reply 1042
Avatar for SKK94
SKK94
1
What is the role of 'markers' involved in the process of making GM plants/animals ??
Reply 1043
Avatar for boxr01
boxr01
Original post by himi-patel
hey,,,im not under standing the answer to the question of january 2011 paper question 5 c(i)............saw the markscheme bt cant understand what it actually means..anyone please help me out..


I dont understand this one either!
Hey guys does anyone have jan 2013 biology unit 5 paper mark scheme?
Original post by LaChiffre
Hey guys does anyone have jan 2013 biology unit 5 paper mark scheme?


http://www.scribd.com/doc/126756230/Edexcel-GCE-Biology-Unit-5-MS. Here's a link for it
I didn't like the rat question on the January 2013 paper. I got the control wrong... ugh the question was so obscure.
Reply 1047
Avatar for SKK94
SKK94
1
Original post by SKK94



Original post by joan2468
Hey, yeah that's what I thought too - but the annotation said it "speeds up cell division" but as far as I know it only allows it to continue and that's why cancer cells can keep dividing to form tumours - because their telomeres never shorten enough for them to stop dividing.


Ok, let's consider the cell cycle, it is controlled by the action of CDK/cyclin complexes right? These complexes phosphorylate parts of the cell in order to initiate the next stage in the cycle.
So what if these complexes phosphorylate telomeres on chromosomes (to stimulate alignment on the equator - i.e to begin metaphase)?
If telomeres are constantly repaired, the chances of successful phosphorylation of telomeres increase, so phosphorylation occurs faster hence metaphase is initiated quicker and speed of cell division increases (?)


^^Is my thought process correct in this? Could someone please verify? :smile:
Original post by boxr01
I dont understand this one either!


i hope such one doesnt come in our exam
has anyone uploaded the pre-release on the mole rats? Ive lost mine, would be a great help as im starting to panic :smile:
Can anyone tell me if this is a good answer to how an impulse is passed along an axon:

1. At the resting potential there is a positive charge outside the membrane and a negative charge inside.
2. When the neurone is stimulate, voltage-gated Na+ channels open, increasing permeability to Na+ and allowing Na+ to flow into the axon. This depolarises the membrane.
3. This creates a local current in the membrane. Na+ moves to the adjacent resting region, creating a change in potential difference across the section of the membrane, initiating a second action potential
4. At the site of the first action potential, Na+ channels close and voltage-gated K+ channels open, causing K+ to move out the axon, triggering depolarisation. The membrane then becomes hyperpolarised.
5. An action potential cannot be generated during the refractory period to ensure the impulse travels in one direction.
6. This process is repeated along the membrane, creating a wave of depolarisation and series of action potentials.

If anyone has any way to improve this (lengthen/shorten or w/e) it would be much appreciated! :smile:
(edited 10 years ago)
Original post by JaayBiology
has anyone uploaded the pre-release on the mole rats? Ive lost mine, would be a great help as im starting to panic :smile:

there are a plenty on this thread just search on the starting pages :smile:
What are the core practicals on this? Spirometer, the maggot respiration one and habitation? Is that all? Also a question on habitation is likely to come up as the past 4 papers have been on spirometer and respiration CP.
Original post by boxr01
I dont understand this one either!


i hope such one doesnt come in our exam
Original post by himi-patel
hey,,,im not under standing the answer to the question of january 2011 paper question 5 c(i)............saw the markscheme bt cant understand what it actually means..anyone please help me out..


I'd assume that the O2 uptake is higher for pyruvic acid than the other two respiratory substrates because o2 acts as the final electron acceptor, and the rate of respiration must be higher with pyruvic acid than the other two? Then you go into details about how pyruvic acid is converted into Acetyl CoA in the link reaction, and how substrates A/B can't perhaps? Then just describe the graph for the rest of the marks, like how B is lower than C etc.

I haven't done that paper so correct me if I'm wrong.
Reply 1055
Avatar for tsr1
tsr1
how does lactate makes NAD available? can someone explain please? thanks
guys since this exam is synoptic sometime questions from earlier units will be asked, what parts of unit one do you think it would worthwhile to go through?
Original post by ViolentMind
guys since this exam is synoptic sometime questions from earlier units will be asked, what parts of unit one do you think it would worthwhile to go through?


Anything that appears in the pre-release as that's the bit that's highly synoptic
Original post by tsr1
how does lactate makes NAD available? can someone explain please? thanks


The conversion of pyruvate to lactate using lactate dehydrogenase produces oxidised NAD. Alternatively perhaps when the lactate is converted back into pyruvate (which then re-enters the process at the Krebbs cycle).
Reply 1059
Avatar for Nathan@
Nathan@
Is this a Pm or Am exam, i think its PM , is that right?

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