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  1. R

    AS Biology P1 MCQs Preparation Thread

    phospholipids make the membrane less fluid or more fluid, but cholestrol regulates the fluidity and makes the membrane more flexible. Saturated or unsaturated hydrocarbon tails of the phospholipids determine the fluidity of the membrane, whereas cholestrols control that fluidity (prevent too...
  2. R

    AS Biology P1 MCQs Preparation Thread

    The mark scheme is for physics! biology is 9700, not 9702 (the mark scheme) :)
  3. R

    AS Biology P1 MCQs Preparation Thread

    Its xylem. The element is vessel and tissue it belongs to is xylem so the correct option is D. This can be deduced from the absence of any cross/end walls in the element and the presence of spots which indicate pits (that are only found in xylem.) For 22) one can clearly identify 2 as phosphate...
  4. R

    AS Biology P1 MCQs Preparation Thread

    For the 1st question the answer is C (144). The working is: 12^2 = 144. Here 12 is the no. of different amino acids and 2 is the no. of amino acids in the chain (its a dipeptide so, 2 amino acids). For question 4 the answer is C. Lysosomes contain most of the hydrolytic enzymes as it is their...
  5. R

    Bio p22 and 52

    have been going through my notes and revising all the topics from Marry Jones :)
  6. R

    AS Biology P1 MCQs Preparation Thread

    there are 20 common amino acids, and since each type of tRNA molecules carries/binds to, only a specific amino acid, 20 tRNA molecules are needed (for 20 amino acids).
  7. R

    Bio p22 and 52

    with protein active was active transport and passive was facilitated diffusion. Without protein active was endocytosis or exocytosis and passive was simple diffusion (or possibly osmosis).
  8. R

    AS Biology P1 MCQs Preparation Thread

    RER have ribosomes as protein synthesis takes place in RER, hence they have mRNA (required for translation). Ribosomes and DNA are also present within mitochondria and chloroplasts so both transcription and translation takes place in these two organelles.
  9. R

    AS Biology P1 MCQs Preparation Thread

    both mitochondria and chloroplasts contain 70S ribosomes for protein synthesis, and since mRNA is required for translation so.... I am not sure about chloroplasts, but mitochondria also contain DNA and transcription (formation of mRNA) takes place in mitochondria.
  10. R

    AS Biology P1 MCQs Preparation Thread

    All 4 of them do
  11. R

    AS Biology P1 MCQs Preparation Thread

    You don't carry out any division, u simply add the time between 1 and 2, and the time between 3 and 4. This sum is approximately equal to 0.07 s
  12. R

    AS Biology P1 MCQs Preparation Thread

    For Q1. options A, B and C are easily eliminated since they are not complementary to the DNA codes for valine. Both option D and E are complementary to the DNA codes for valine, but since the question asks about mutation in which single nucleotide/base has been substituted (from CTT of glutamic...
  13. R

    AS Biology P1 MCQs Preparation Thread

    0 kPa is the water potential of pure water, whereas water in xylem contains dissolved mineral ions so it has a lower (less than o) water potential. :) The question asks about salty water which is unsuitable for growth. Water moves from the xylem to the soil water (which is why it is unsuitable...
  14. R

    AS Biology P1 MCQs Preparation Thread

    Elimination can be employed here. Option D is factually incorrect whereas options A, B and C are factually correct. However, the conclusions in options A and C cannot be drawn from the results/graph. Only the statement in option B can be drawn as a conclusion from the results/graph. This is...
  15. R

    AS Biology P1 MCQs Preparation Thread

    Xylem transports water and mineral ions so the sucrose concentration in xylem is insignificant (some surcrose may entered xylem by diffusion.) The graph/lines of phloem and leaves are identical indicating the active loading of sucrose from leaves to phloem. From 0 00 to 06 00 no photosynthesis...
  16. R

    Bio p22 and 52

    Yes, it was difficult to distinguish it as either RER or SER, but it was RER since they had asked about the structure's importance to specific role of plasma cells. RER is required for synthesis of proteins and hence antibodies, since antibodies are (glyco)proteins. SER has no importance to the...
  17. R

    AS Biology P1 MCQs Preparation Thread

    For question no. 30 its option D because aerobic respiration requires both glucose and oxygen, both of which are brought to the muscles via the blood, so an increase in volume of blood flow would mean that more glucose and oxygen are provided to muscles and more waste products are carried away...
  18. R

    AS Biology P1 MCQs Preparation Thread

    For no. 15 the correct answer is B, because as sucrose concentration increases water potential decreases and becomes more negative. As the water potential decreases less water moves into the plant tissue via osmosis, so there is less turgidity. For no. 24 movement of sucrose from leaf cell to...
  19. R

    AS Biology P1 MCQs Preparation Thread

    Basically the numerical value of resolution increases, but resolution itself decreases. Light microscope has a resolution of 200nm while electron microscope has a higher resolution of 0.5 nm, However the numerical value is higher for light microscope (200). Basically the numerical value tells us...
  20. R

    Bio p22 and 52

    I thought so too, i found this from google images, although there were many photomicrographs of plasma cells, I immediately recognized this one as the one given in our paper. :)
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