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A level Biology: Post your doubts here!

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ashcull14

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shazmina said:
http://onlineexamhelp.com/wp-content/uploads/2014/08/9700_s14_qp_12.pdf
Can any1 help me with question number 18 of this paper :)
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well im not sure bout this but according to me its A
because
the main highlighted terms are nuclear division and cell division
B= the mass of DNA doesnt get halved again after anaphase
C= Doesnt refer to nuclear division ...refers to cancer precisely talking about cell division
D= this ones a bit confusing because it refers to nuclear division (mitosis) and cell division (cell repair and replacement) however, what i think is that it only discusses the importance of mitosis ...doesnt focus on the process (mechanism) of mitosis and cell division but is relevant to the consequences followed by the process
 
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ilovepineapples

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Hey guys, anyone from A2? There's exactly 25 days left till biology paper 5. How are you guys revising? I'm going over the syallbus for the third time after that just going to do pastpapers
 
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suannlow

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Hi guys, can anyone tell me during phloem loading, hydrogen ion is passed from the companion cell into the cell wall or cytoplasm of the plant cell? My course book stated there it passes into the cell wall, causing a high concentration of it in apoplast. But my lecturer told me that it was pumped into the cytoplasm of it and the older version of coursebook said so. Thank you :)
 
Karim Nabil

Karim Nabil

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suannlow said:
Hi guys, can anyone tell me during phloem loading, hydrogen ion is passed from the companion cell into the cell wall or cytoplasm of the plant cell? My course book stated there it passes into the cell wall, causing a high concentration of it in apoplast. But my lecturer told me that it was pumped into the cytoplasm of it and the older version of coursebook said so. Thank you :)
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Be more specific!
 
Mahnoorfatima

Mahnoorfatima

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suannlow said:
Hi guys, can anyone tell me during phloem loading, hydrogen ion is passed from the companion cell into the cell wall or cytoplasm of the plant cell? My course book stated there it passes into the cell wall, causing a high concentration of it in apoplast. But my lecturer told me that it was pumped into the cytoplasm of it and the older version of coursebook said so. Thank you :)
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Follow the coursebook. H+ ions move into the cell wall.
 
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ilovepineapples

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For those in AS GET THE REVISION GUIDE. it will help you SO much. I got if for free on an app called scribd but I think now you have to pay for it, otherwise I think it is available in stores. With hard work, past papers and that your bound to get a high A. Do yourself a favour and get it
 
princessnoor

princessnoor

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Mahmood Magdy said:
Well P52 Q1b(i), they are asking for the value of t for INTERNODE LENGTH , X1 and X2 are the mean values of both the types of leaves. In the table 1.1, the values are written in the form of Mean +- Standard deviation, therefore 23-19, S2 and N2 are the standard deviation and the number of samples and thus 3^2 / 30, and therefore the final answer 8.9.

Nov 2010 P53 Q1c(i), the formula is for the Standard error, simply you will have to divide by the square root of the number of samples, therefore, you will divide by square root of 12, and then round the answer of 1.15 to 1 :D

Nov 2011 P53 Q2b(ii) , Chi-square test, you need the total number of samples first, which will simply be 112 (40+72) or from table 2.1 add all the values of Cross1, as offspring with tail is recessive lets say, 0.25 * 112 = 28, and therefore 112-28= 84. Just put these values in the formula given and add both these results at the end to get 6.86(after rounding to 2dp)
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Thanku for replying, but i dont understand how the sample number is 12 in Q1c(i) and y multiply 2.5 with 112 in Q12

And plz explain me these too nov 9 p51 Q2c ii, june9 p5 Q3 biii ( here erorr bars overlap but in ms its written no overlap)
 
Mahnoorfatima

Mahnoorfatima

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ilovepineapples said:
For those in AS GET THE REVISION GUIDE. it will help you SO much. I got if for free on an app called scribd but I think now you have to pay for it, otherwise I think it is available in stores. With hard work, past papers and that your bound to get a high A. Do yourself a favour and get it
Click to expand...
Is it the exdexel one?
 
A

ashcull14

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An enzyme hydrolyses the two heavy polypeptide chains of an antibody molecule. The hydrolysis occurs at the hinge region and breaks the antibody into three fragments. How many of these fragments are able to bind to antigens?
A=0
B= 1
C= 2
D=3
 
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