IGCSE/GCSE/O & A Level/IB/University Student Forum
Qualification => Subject Doubts => GCE AS & A2 Level => Sciences => Topic started by: unknown 101 on May 23, 2010, 12:27:32 am
-
june 2005 Q2, please explain how u got the answer :S
pretty annoying question!!!
-
An easy way is to change it to metres first , then to nanometres ...
Soo its 0.4 micrometres then multiply by 10-6 you will get it in metres. Now from metres to nanometres you multiply the answer by 109
If you get used to it , a simpler way would be just to multiply by 103
So the answer would be 400nm :D
Hope it helped :D
-
who's here for you except your classmate (A) :P
look, micrometers are to the power of -6 and nano meters are to the power of -9, ya3ni there is a difference of -3 between them.
so all do is divide (because your going from a larger value to a smaller value) by 1 x 10^-3
so 0.4 / 1 x 10^-3= 400 nano meters :)
-
An easy way is to change it to metres first , then to nanometres ...
Soo its 0.4 micrometres then multiply by 10-6 you will get it in metres. Now from metres to nanometres you multiply the answer by 109
If you get used to it , a simpler way would be just to multiply by 103
So the answer would be 400nm :D
Hope it helped :D
ya thanks it helped ;)
-
@rakan
Thanks bro i get it, bas ya 3'abi edit you post cuz at the end your multiplying by 1 x 10^-3 not dividing!! ;)
-
:P
-
ya thanks it helped ;)
np man ;)
Anywayz I was having trouble with the June 08 paper.. Plz help
Q12,18,20,21,26,27
I know they're a lot, so ure help will be much appreciated :)
-
np man ;)
Anywayz I was having trouble with the June 08 paper.. Plz help
Q12,18,20,21,26,27
I know they're a lot, so ure help will be much appreciated :)
dont worries bro thats why we are here ;)
Q12: ok it tells you that they increased the temp by 10, so that means that rate of raction will double ( therefore the curve must be steeper)
then it tells you that they added extra substrate so that means amount of product must be more!! so the only curve which is steeper AND has more product than X is curve B
Q18:
1) forms cells of equal size to the parent cell ( definantely wrong cuz the daughter cells are always smaller )
2) forms genetically identical cells ( this is right as it contains the same DNA sequences o genetically identical )
3) semi-conservative replication of DNA ( this has nothing to do with the mitotic cell cycle, as the DNA is replicated in the interstage ( before entering mitosis), and this is probabley where you got confused )
so the right answer is only 2)
Q20: so from your knowledge about metaphase, the centrioles are at opposite poles, and the sister chromatids arrange themselves on the equator of the cell, etc. so now the cell will be entering anaphase
so the distance between centromeres and poles of spindle decreases as know the cell is in anaphase stage where the chromatids will split appart ( so this part is 1 on the graph )
and the distance between centromeres of sister chromatids increases because they are being pulled towards opposite poles ( so this is 2 on the graph)
and the distance between poles of spindle will also increase in disance cuz they are also at opposite poles now ( this is 3 on the graph )
Q21:
ok so here is the DNA codon from the question, so if you transcribe it it will give the mRNA ( so im goind to transcribe it under the original codon )
T C C A C T C G A T G C
A G G U G A U G A G C U A C G ( transcribed part )
ok so if a mutation occurs in the bold part and the (C) switches with (T) then the stop codon ( UAG ) would be formed
so answer is B
Q26: if look at the options u have:
A cohesive tension forces increased during the day ( if cohesive forces between water molecules increase then more water would move through the xylem, increasing the diameter of tree, this is the right answer)
B mass flow of sucrose increased during the night ( if sucrose was being transported at the night then the diameter of the tree must increase, but in the in the graph it decreases at night, so this answer is wrong )
C root pressure decreased during the day ( if root pressure decreased that means less water would be transported in the day so the diameter of tree would decrease, but it increases in the day, so this answer is wrong! )
D thermal expansion and contraction of water in the tree ( expansion and contraction of water does not neccesrially mean that the amount of water transported would increase or decrease, so this answer is wrong as well )
Q27: ok its askin about the solute potential in the phloem SEIVE TUBES, so it has to be low otherwise assimilates would not move inside the seive tube
and lignification is only found on xylem vessels, so lignification must be absent! so answer is C
finally im done, damn that was loooooonnnngg!!!!!
hope this helped.. :) ;)
-
dont worries bro thats why we are here ;)
Q12: ok it tells you that they increased the temp by 10, so that means that rate of raction will double ( therefore the curve must be steeper)
then it tells you that they added extra substrate so that means amount of product must be more!! so the only curve which is steeper AND has more product than X is curve B
Q18:
1) forms cells of equal size to the parent cell ( definantely wrong cuz the daughter cells are always smaller )
2) forms genetically identical cells ( this is right as it contains the same DNA sequences o genetically identical )
3) semi-conservative replication of DNA ( this has nothing to do with the mitotic cell cycle, as the DNA is replicated in the interstage ( before entering mitosis), and this is probabley where you got confused )
so the right answer is only 2)
Q20: so from your knowledge about metaphase, the centrioles are at opposite poles, and the sister chromatids arrange themselves on the equator of the cell, etc. so now the cell will be entering anaphase
so the distance between centromeres and poles of spindle decreases as know the cell is in anaphase stage where the chromatids will split appart ( so this part is 1 on the graph )
and the distance between centromeres of sister chromatids increases because they are being pulled towards opposite poles ( so this is 2 on the graph)
and the distance between poles of spindle will also increase in disance cuz they are also at opposite poles now ( this is 3 on the graph )
Q21:
ok so here is the DNA codon from the question, so if you transcribe it it will give the mRNA ( so im goind to transcribe it under the original codon )
T C C A C T C G A T G C
A G G U G A U G A G C U A C G ( transcribed part )
ok so if a mutation occurs in the bold part and the (C) switches with (T) then the stop codon ( UAG ) would be formed
so answer is B
Q26: if look at the options u have:
A cohesive tension forces increased during the day ( if cohesive forces between water molecules increase then more water would move through the xylem, increasing the diameter of tree, this is the right answer)
B mass flow of sucrose increased during the night ( if sucrose was being transported at the night then the diameter of the tree must increase, but in the in the graph it decreases at night, so this answer is wrong )
C root pressure decreased during the day ( if root pressure decreased that means less water would be transported in the day so the diameter of tree would decrease, but it increases in the day, so this answer is wrong! )
D thermal expansion and contraction of water in the tree ( expansion and contraction of water does not neccesrially mean that the amount of water transported would increase or decrease, so this answer is wrong as well )
Q27: ok its askin about the solute potential in the phloem SEIVE TUBES, so it has to be low otherwise assimilates would not move inside the seive tube
and lignification is only found on xylem vessels, so lignification must be absent! so answer is C
finally im done, damn that was loooooonnnngg!!!!!
hope this helped.. :) ;)
Man that was great :D I'm sorry yeh they were a lot of questions :D Anyway if u want aanything just post it up here and I'll be glad to help :)
-
May/June 2006 Question 30
-
Can I have an explanation for the answer? :-[
-
this question was withdrawn from the examination anyways.
but here'sthe solution.
if atrio-ventricular valves close then this means that blood has already flown into the ventricles and pressure is growing in it. which is from 1-2 in the graph, it also could mean that blood is being filled into the atria from the pulmonary veins and therefore pressure in the ventricle is decreasing beacuse all the blood it has is passing to aorta which is from 3-4on the graph. so you add those times, they add up to 0.07s which is C
but like i said, it was with drawn from the examination because no one was able to read the graph properly.
-
Man that was great :D I'm sorry yeh they were a lot of questions :D Anyway if u want aanything just post it up here and I'll be glad to help :)
any time ;)