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A level Biology: Post your doubts here!

Lola_sweet

Lola_sweet

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Farhad221 said:
Q15
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The SI unit for time is Seconds, so while recording results our results should always be in seconds thus it cant be for A and B
and for precise results u always right ur answer to the nearest second (p3 tip) so it cant be D
thus we r left with C :)
 
Lola_sweet

Lola_sweet

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Farhad221 said:
Q21
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if u see the first part of the qs its written tht BRCA1 or BRCA2 lead to the heredity of breast cancer, and we knw tht cancer is formed by mutation in the gene causing an abnormal gene to be produced. So for breast cancer to occur these 2 genes have to produce abnormal or no protein.
Also p53 is a tumour supressor gene (a gene which protects a gene from forming a tumour) so this has to produce abnormal or no protein in order to lead to breast cancer.
Thus its D
 
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Studydayandnight

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Also for this magnification question, to find the image size, do I measure the length of the entire picture? Or just the width of a single Xylem vessel??
 

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qwertypoiu

qwertypoiu

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Studydayandnight said:
Also for this magnification question, to find the image size, do I measure the length of the entire picture? Or just the width of a single Xylem vessel??
Click to expand...
just measure the length of the scale bar labelled 50 micrometers.
Then magnification = image/ real = (what you measure on your ruler) / (50 micrometers.)
 
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Studydayandnight

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HELP! How do we find the diameter?

I bet I am going wrong with the conversions or something :/
 

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A

ashcull14

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qwertypoiu said:
As explained before can't do first question :)
Q2:
Movement of sucrose from chloroplast to phloem does NOT include mass flow.
Mass flow happens when sucrose is translocated from source to sink.
The sucrose moving from source (chloroplast in this case) to the phloem is just the initial step to this, and only involves the companion cell pumping H+ ions using ATP to bind sucrose to H+ ions and make them travel together against sucrose concentration gradient through a co-transporter molecule.
If 1 is wrong, obviously the only option left is D. Once inside the companion cell, H+ ions are detached and sucrose molecules naturally move down their concentration gradient into the phloem elements, this probably involves both the symplast and apoplast transport.
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thnk u life saver :D
 
Farhad221

Farhad221

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Lola_sweet said:
The SI unit for time is Seconds, so while recording results our results should always be in seconds thus it cant be for A and B
and for precise results u always right ur answer to the nearest second (p3 tip) so it cant be D
thus we r left with C :)
Click to expand...
it is C
 
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