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  1. R

    A level Biology: Post your doubts here!

    part of body: bone marrow similarities: in both structures the H atom is below C atom 1 or OH is above C 1 atom in ring structures of both ribose glucose. Also, the H and OH are at same place on C atom 2. differences: B-glucose has 6 C atoms while ribose has 5 C atoms or B-glucose is 6-membered...
  2. R

    A level Biology: Post your doubts here!

    Q1. (a) (ii)......... http://www.xtremepapers.com/papers/CIE/Cambridge%20International%20A%20and%20AS%20Level/Biology%20(9700)/9700_w10_qp_23.pdf
  3. R

    A level Biology: Post your doubts here!

    True! However, most cells have membrane protein channels called aquaporins, which allow quicker (facilitated) diffusion of water, but that i guess it is not in AS level, so in general at AS level they tell us that phospholipid bilayer acts as a barrier to water and CIE also uses this general...
  4. R

    A level Biology: Post your doubts here!

    Phosphate heads are responsible for the orientation of the phospholipid bilayer. In questions related to how the structure of a phospholipid allows it to form a bilayer, you have to mention that the phosphate heads are hydrophilic and therefore, water attracting so they face outwards towards the...
  5. R

    A level Biology: Post your doubts here!

    Answer: There is complementary base pairing in a DNA molecule/double helix, so the double helix unwinds to give two complementary strands of DNA. Each strand acts as a template for the synthesis a complementary DNA strand, so two new DNA double helices are formed with each double helix having...
  6. R

    A level Biology: Post your doubts here!

    At source (leaf) proton pumps of transfer/companion cells pump protons (H+) to surrounding mesophyll cells via active transport, using energy from ATP. The protons then diffuse back into the transfer cells, down their concentration gradient, carrying sucrose along with them which is known as...
  7. R

    A level Biology: Post your doubts here!

    hmmm, thanks for the insight! better do it then! :) also, uses of ions are no longer in our syllabus except for nitrates and magnesium, no harm in doing them as well i guess! :)
  8. R

    A level Biology: Post your doubts here!

    Hey, do we also have to do the electrocardiogram as well, besides the usual pressure graph for cardiac cycle???
  9. R

    A level Biology: Post your doubts here!

    can someone please explain why triglycerides release more energy on respiration than carbohydrates. This question has been repeated more than once, but i don't understand the points in the mark schemes, what is the chemistry behind it???
  10. R

    GT for Chemistry paper 22 AS.

    There were definitely 6 marks for the 3 conditions, 2 marks for each, 1 marks for stating that the rate of formation increases and another mark for stating how......i think so.
  11. R

    Chem p22

    If its chlorine then both sodium and sulfur are correct answers....no? :| bcuz i wrote sodium, i hope sodium isnt wrong :\ and i m sure sulfur is correct! :D
  12. R

    Chem p22

    Was it burning in oxygen or burning in chlorine?? :\
  13. R

    Chemistry Paper 22: Discussion and Grade Threshold

    It was AlCl3 and it reacts with water to form Al2O3 and HCl. The reaction of chlorides with water was hydrolysis and the enthalpy change was -129. The empirical formula was C6H8O7 and yes the compound had one ketone group and 2 primary alcohol groups! :)
  14. R

    Chem p22

    For Question 1, the element for liquid chloride was either phosphorus or silicon. For the coloured flame, it was sodium since it burns with a yellow flame in Cl2. For observations it could have been: Al glows, white solid formed/appears, Cl2 colour fades away/disappears (any 2) AlCl3 reacts with...
  15. R

    Chemistry Paper 2

    For the empirical formula part: C was 37.5 %, H was 4.17% and O was 58.3% so, C:H:O = 37.5/12 : 4.17/1 : 58.3/16 = 3.125 : 4.17 : 3.644 then divide all values by lowest value 3.125 so, = 1 : 1.334 : 1.166 then multiply sll values by 6 to obtain simplest whole no. ratio...
  16. R

    Chem P2 any guesses ?????

    hmmm, i m guessing the flow diagram for haber process, the diagram for electrolysis of molten aluminium oxide, a question on Boltzmann distribution curve, a question related to conditions, reagents and observations of certain reactions. But this is just a lame guess!!! :P Like they say 'Hope for...
  17. R

    Beaconhouse Defence, Lahore. What about you? :)

    Beaconhouse Defence, Lahore. What about you? :)
    • rogue94
    • Profile post
  18. R

    no problem! :) I m in A-1 and i have to give my AS levels in this coming May/June session

    no problem! :) I m in A-1 and i have to give my AS levels in this coming May/June session
    • rogue94
    • Profile post
  19. R

    Also, download the Mary Jones revision guide and read the practical section of the book..here is...

    Also, download the Mary Jones revision guide and read the practical section of the book..here is the link: http://www.xtremepapers.com/community/threads/biology-revision-guide-by-mary-jones.13213/ hope it helps! :)
    • rogue94
    • Profile post
  20. R

    download the new 2014 syllabus from here...

    download the new 2014 syllabus from here: http://www.cie.org.uk/qualifications/academic/uppersec/alevel/subject?assdef_id=734 Go through the practical section, its gives a good layout of all the required skills, previously not given in the syllabuses.
    • rogue94
    • Profile post
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