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  1. I

    biology paper 1 doubts

    Net primary productivity = energy absorbed - energy lost in respiration energy absorbed = 1,000,000 - 990,000 = 10,000 energy lost in respiration = 5,000 (shown in the diagram) Net primary productivity = 10,000 - 5,000 = 5,000 Percentage of light energy converted to net primary productivity =...
  2. I

    biology paper 1 doubts

    4) Many prokaryotes have chlorophyll which carries out photosynthesis. In plants, chlorophyll is contained within chloroplasts. 38) Nitrifying bacteria require aerobic conditions (soil with oxygen) to convert ammonium ions into nitrates. Without oxygen (anaerobic conditions), the opposite takes...
  3. I

    biology paper 1 doubts

    Plants' cell walls are fully permeable. That is, they allow anything to pass through, even water. That is, until the cell is completely turgid then it won't allow any net movement of water in to prevent bursting.
  4. I

    biology paper 1 doubts

    Both form memory cells.
  5. I

    biology paper 1 doubts

    No, triglycerides do NOT have any hydrogen bonds as they don't have any sufficiently positive hydrogen atom in its structure. Even if, the molecule is too large to be affected by one or two hydrogen bonds.
  6. I

    biology paper 1 doubts

    Dipeptide = 2 amino acids You have 12 possibilities for the first amino acid You also have 12 possibilities for the second amino acid So you have a total of 12 x 12 = 144 possibilities for the dipeptide.
  7. I

    biology paper 1 doubts

    Ribosome = 20 nm in prokaryotes and 22 nm in eukaryotes Centrioles: length = 700 nm, diameter = 250 nm EDIT: Also, the thickness of a cell membrane is 7 nm, which makes it the thinnest organelle.
  8. I

    biology paper 1 doubts

    Sucrose is actively transported to the phloem (B) from the leaves (mesophyll cells/A) Sucrose is unloaded (taken in) near the roots (C and D). So sucrose is most concentrated in the phloem near the leaves (B). Higher concentration = more negative water potential. So the answer is B.
  9. I

    biology paper 1 doubts

    More negative = less water potential = more dissolved solutes Less negative = more water potential = less dissolved solutes (purer water) I've fully explained this in one of my earlier posts yesterday, check somewhere around page 2 or 3.
  10. I

    biology paper 1 doubts

    Water potential is generally negative. The higher the water potential, the purer the water is. The lower the water potential, the more solutes dissolved in it. Water moves from an area of high water potential to an area of low water potential. So if the water potential of A is less negative than...
  11. I

    biology paper 1 doubts

    The case mentioned in the question is known as haplodiploidy (a form of parthenogenesis). It's a bit complicated to explain fully, and may seem extremely confusing. But in the normal cases that we took, producing the unfertilized eggs (gametes) is a source of variation in itself. To answer...
  12. I

    biology paper 1 doubts

    Yeah, one more thing. Be 100% that you know exactly what the question is asking for. Believe me, I lost many marks in the first two papers for this. After realizing this mistake by the third past paper, I never got below a full mark from June '07 till June '11 :)
  13. I

    biology paper 1 doubts

    That's awesome! Now all you have to do is quickly revise the concepts which you got wrong most of the time
  14. I

    biology paper 1 doubts

    I'm guessing you're not 100% confident about the material. I strongly suggest you quickly revise the book. If you can't do that, then at least find some notes online and look at them thoroughly. After that, solve just the last few past papers (2011-2012) and you should be good to go! Good luck :)
  15. I

    biology paper 1 doubts

    Wait, that completely goes against almost everything I've learnt about this subject. In spermatogenesis, you start with a primary spermatocyte which is diploid. After passing through meiosis I and II (which results in halving the chromosome number), then you will have immature spermatids (which...
  16. I

    biology paper 1 doubts

    First of all, I really like your desire to learn more :) As for question 16, you need to know two (very obvious) things: 1) Oxygen is needed for active transport (to break down food for energy) 2) Air contains oxygen With or without oxygen, the rate of uptake of 3-carbon sugar was the same...
  17. I

    biology paper 1 doubts

    The Bohr shift already allows maximum rate of dissociation of oxygen from haemoglobin, so it can't be a limiting factor. However, how quickly RBCs can deliver oxygen is a limiting factor. If the volume of blood flow through the muscles is low per unit time, not enough RBCs can be there to...
  18. I

    biology paper 1 doubts

    The process of PRODUCING the eggs creates variation. They produce eggs through meiosis which involves independent assortment and crossing over (which leads to variation).
  19. I

    biology paper 1 doubts

    A, B, C, and D are four different bases (adenine, guanine, cytosine, and thymine). They want to know which one is adenine. By looking at sample 3, we can know this is a piece of RNA because it has uracil instead of thymine. This also proved to us that choice C is thymine because it is absent in...
  20. I

    Biology 33, how was it?

    It's not about the centre or the country, people in my class for answers between 0.2 and 0.5. And maybe you're right, some people might get different types of seeds! I'm from Jordan.
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