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*Biology Paper 5 tips*

I

Irfan1995

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Soldier313 said:
Aoa wr wb :)
I need some help with a few qns

For qn 2 c of this paper, why does the rate of loss increase??

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s12_qp_52.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s12_ms_52.pdf

____________

For qn 2 a of this paper, we need a stain, someone previously told me we use Giemsa, but i was just wondering, is there another one that's mentioned in the syllabus?

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_51.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_ms_51.pdf
____________

For qn 2 d i of this paperm can someone please elaborate the ms answer ?

http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_qp_52.pdf
http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Biology (9700)/9700_s11_ms_52.pdf

Thank you so much :)
Click to expand...

May/June '12:
2)c) EDIT: Really sorry about the wrong information I provided earlier. After re-reading the question, the most probable correct answer was that the high concentration of ethanol would affect the membrane permeability allowing water to move out much easier. Soldier313

May/June '11 (51):
I'm familiar with silver stainings which clearly show proteins and DNA. There's also Acridine Orange (AO) which specifically stains DNA and RNA (attracts charged particles). There's also DAPI, but you must shine UV light on it to make it visible. It binds to the A-T bonds in DNA. There are others like ethidium bromide, but these stain only cells that are undergoing apoptosis (cell death). It's mainly used with AO.
I'm not sure if any of those are included in the syllabus.

May/June '11 (52):
I'll copy the section from the examiner's report concerning this question:
"(d) Candidates needed to compare the results for FF-MAS with the results for the other known
activators of the membrane receptor LXR alpha. Many did not recognise that the 0.00
concentrations for all the tested activators represented the range of natural stimulation of meiosis.
(i) Almost all candidates stated that the original hypothesis was correct. Although it is true that
FF-MAS stimulates meiosis, it is not true that it does so by stimulating the LXR alpha
receptor. The known activators of this receptor show relatively little stimulation of meiosis if
the range of natural stimulation is taken into account. "

This didn't make much sense to me; maybe you'll understand it better than I would.
 
Soldier313

Soldier313

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Irfan1995 said:
May/June '12:
2)c) If the water has 70% ethanol, then the water potential would be extremely low. This drives the rate of transpiration to increase in order to maintain a balance of water potentials.

May/June '11 (51):
I'm familiar with silver stainings which clearly show proteins and DNA. There's also Acridine Orange (AO) which specifically stains DNA and RNA (attracts charged particles). There's also DAPI, but you must shine UV light on it to make it visible. It binds to the A-T bonds in DNA. There are others like ethidium bromide, but these stain only cells that are undergoing apoptosis (cell death). It's mainly used with AO.
I'm not sure if any of those are included in the syllabus.

May/June '11 (52):
I'll copy the section from the examiner's report concerning this question:
"(d) Candidates needed to compare the results for FF-MAS with the results for the other known
activators of the membrane receptor LXR alpha. Many did not recognise that the 0.00
concentrations for all the tested activators represented the range of natural stimulation of meiosis.
(i) Almost all candidates stated that the original hypothesis was correct. Although it is true that
FF-MAS stimulates meiosis, it is not true that it does so by stimulating the LXR alpha
receptor. The known activators of this receptor show relatively little stimulation of meiosis if
the range of natural stimulation is taken into account. "

This didn't make much sense to me; maybe you'll understand it better than I would.
Click to expand...


Thanx a lot!

But just a few clarifications:
Okay for the MJ/12 P52 qn, the question is referring to rate of loss of chloride ions, not rate of transpiration :/

And for the MJ/11 P52 qn, i didn't get the examiner report either when i read it :/

Thanx once again.
 
I

Irfan1995

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Soldier313 said:
Thanx a lot!

But just a few clarifications:
Okay for the MJ/12 P52 qn, the question is referring to rate of loss of chloride ions, not rate of transpiratio :/

And for the MJ/11 P52 qn, i didn't get the examiner report either when i read it :/

Thanx once again.
Click to expand...

May/June '12: You're right, sorry about the confusion! I already edited my answer to suit the actual explanation.

May/June '11: Actually, it does make sense.
In the question, they tell you that the three other chemicals are known to stimulate LXR alpha. So although FF-MAS increase the stimulation of meiosis, it doesn't do it by stimulating LXR alpha; it must be through a different way. This is because the other three chemicals that stimulate LXR alpha did not have any effect, so maybe LXR alpha doesn't have anything to do with meiosis stimulation!
 
K

Kinjal

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Hi guys..
I jus read about all the error bars discussion. According to what you're saying,we multiply 2 with the value of stadard error and then plot it right? Then why does the ms of w10 53,qn 1c) (iii) say you jus take +/- stndrd error? It also says accept +/- stndrd deviation! :S
Im really sorry for making you repeate the explanation again,im jus very confused :/
 
M

Marks&Spencers

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Irfan1995 said:
May/June '12: You're right, sorry about the confusion! I already edited my answer to suit the actual explanation.

May/June '11: Actually, it does make sense.
In the question, they tell you that the three other chemicals are known to stimulate LXR alpha. So although FF-MAS increase the stimulation of meiosis, it doesn't do it by stimulating LXR alpha; it must be through a different way. This is because the other three chemicals that stimulate LXR alpha did not have any effect, so maybe LXR alpha doesn't have anything to do with meiosis stimulation!
Click to expand...

Ok, Irfan1995, I read that examiner's report like 10 times and didn't get it. Look, you are a great person and all, and you do deserve all good because you help people out as much as you can. Now I have a request, which I ask from the bottom of my heart, will you please extend your favours, and remember the poor brothers and sisters, and try not to get the full mark tomorrow? We're both doing the same variant, and with people like you in this world, the curve is going to be so high I won't get that A, or even a B. I'm not asking for a lot, just try to push yourself to lose like 2-3 marks. Please?
 
knowitall10

knowitall10

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D0cEngi said:
I know the formula but I don't know how to use it. :D
There is a question in Oct/nov 2012 p52 where he asked for the degrees of freedom but I don't know form where the hell he took 40 as the no. of samples. :/
Click to expand...

how many samples are there?
 
Soldier313

Soldier313

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Irfan1995 said:
May/June '12: You're right, sorry about the confusion! I already edited my answer to suit the actual explanation.

May/June '11: Actually, it does make sense.
In the question, they tell you that the three other chemicals are known to stimulate LXR alpha. So although FF-MAS increase the stimulation of meiosis, it doesn't do it by stimulating LXR alpha; it must be through a different way. This is because the other three chemicals that stimulate LXR alpha did not have any effect, so maybe LXR alpha doesn't have anything to do with meiosis stimulation!
Click to expand...


Oh okay! thanx a lot! Alhamdulillah, it's clear now!
 
I

Irfan1995

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Marks&Spencers said:
Ok, Irfan1995, I read that examiner's report like 10 times and didn't get it. Look, you are a great person and all, and you do deserve all good because you help people out as much as you can. Now I have a request, which I ask from the bottom of my heart, will you please extend your favours, and remember the poor brothers and sisters, and try not to get the full mark tomorrow? We're both doing the same variant, and with people like you in this world, the curve is going to be so high I won't get that A, or even a B. I'm not asking for a lot, just try to push yourself to lose like 2-3 marks. Please?
Click to expand...

Do you really think that if one person gets a full mark, then that would make a significant difference in the curve? Remember that there are thousands of candidates sitting for this exam as well. In fact, there is a large proportion of Indians/Pakistani/Other genius Asians who intend to score very high marks. I don't think that one individual will make the difference. Not to mention, one of the Hadith from the Prophet Muhammad (ص) actually forbids me from doing this.
I think it's best to raise your own marks rather than trying to bring down the standard.

EDIT: I really appreciate the compliments though :)
And if there's any thing I can clarify in the Examiner's Report, please ask!
 
N.M

N.M

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D0cEngi said:
I know the formula but I don't know how to use it. :D
There is a question in Oct/nov 2012 p52 where he asked for the degrees of freedom but I don't know form where the hell he took 40 as the no. of samples. :/
Click to expand...


20 for 1 n 20 for the other sample, so makes 40.
 
M

Marks&Spencers

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Irfan1995 said:
Do you really think that if one person gets a full mark, then that would make a significant difference in the curve? Remember that there are thousands of candidates sitting for this exam as well. In fact, there is a large proportion of Indians/Pakistani/Other genius Asians who intend to score very high marks. I don't think that one individual will make the difference. Not to mention, one of the Hadith from the Prophet Muhammad (ص) actually forbids me from doing this.
I think it's best to raise your own marks rather than trying to bring down the standard.

EDIT: I really appreciate the compliments though :)
And if there's any thing I can clarify in the Examiner's Report, please ask!
Click to expand...

LOL! Why so serious? You do realise I'm just kidding right? I swear sometimes smart people never get simple jokes. I seriously just intended a joke o_O
I did mention "with people like you", so I didn't say you were the one and only, and boy I know what Asians do! :)
Oh believe me, I am trying my best to bring my standard up here, and there is a difference between the marks I used to get when I first started solving and now, so I'm trying here!
Ok, just so I don't upset you, you do your best and get that full mark, and may Allah help us all tomorrow, and may we all achieve good grades. :)
 
I

Irfan1995

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Marks&Spencers said:
LOL! Why so serious? You do realise I'm just kidding right? I swear sometimes smart people never get simple jokes. I seriously just intended a joke o_O
I did mention "with people like you", so I didn't say you were the one and only, and boy I know what Asians do! :)
Oh believe me, I am trying my best to bring my standard up here, and there is a difference between the marks I used to get when I first started solving and now, so I'm trying here!
Ok, just so I don't upset you, you do your best and get that full mark, and may Allah help us all tomorrow, and may we all achieve good grades. :)
Click to expand...

Good luck :)
 
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Xainab

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Kinjal said:
Hi guys..
I jus read about all the error bars discussion. According to what you're saying,we multiply 2 with the value of stadard error and then plot it right? Then why does the ms of w10 53,qn 1c) (iii) say you jus take +/- stndrd error? It also says accept +/- stndrd deviation! :S
Im really sorry for making you repeate the explanation again,im jus very confused :/
Click to expand...

I want someone to clarify this too, please? Why dont we multiply the standard error by 2 in this case?
 
M

Marks&Spencers

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Irfan1995 I need a clarification in the examiner's report this time. In the sources I have read so far, and in the comment which you and many others gave regarding the standard error and the bars, I understood that we multiply by 2. Now I ask, as another person already did in this post, why did they say in the examiner's report of w10 p53 1c)(iii) (and mark scheme as well), only +/- the standard error about the bar graph, not 2x standard error?
 
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