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  1. I

    A level Biology: Post your doubts here!

    To summarize the entire point: Insulin is a protein made up of two polypeptides/chains (A and B) joined by disulphide bonds and doesn't contain methionine (a specific amino acid). Each polypeptide is synthesized from one gene, so there are two genes which code for insulin (one for each...
  2. I

    A level Biology: Post your doubts here!

    1) Thick waxy and waterproof cuticle - reduces water loss and heat absorption (since it reflects off some sunlight) 2) Motor cells which allow it to curl - minimizes water potential gradient --> reduces transpiration rate --> saves water 3) Long branching roots - allow it to absorb as much water...
  3. I

    A level Biology: Post your doubts here!

    Sorry! I misread your question. Anyways, the lumen is approximately 8 units wide (from 1.35 - 9.25) on the eyepiece graticule. 8 units on the eyepiece graticule (from 0 - 8) is approximately 9 units on the ruler (from 2.0 - 2.9) (on the second picture) 9 units on the ruler is 0.9 mm (since each...
  4. I

    A level Biology: Post your doubts here!

    I don't think we're asked to draw any random cell. But you may be asked to draw the structure of ATP, mitochondria, chloroplasts, plant adaptations (drawing a plant with a thick cuticle, long branching roots, C4 plant structures etc...) and probably human reproductive organs.
  5. I

    A level Biology: Post your doubts here!

    Just draw the three layers. Ignore the details outside the artery. It must be large and proportional (it must be like an oval, not a circle). The mark scheme provides a good example of a drawing.
  6. I

    S1, how was it? My answers, please put yours to compare.

    The IQR stays, the same. Sorry for the confusion :(
  7. I

    S1, post your doubts here....

    The mean, median, quartiles, and the interquarile range will ALL decrease by 5 minutes The standard deviation will stay the same I'm pretty sure about my answer. And yes, k = 1/5 = 0.2; remember that they gave you the cumulative frequency table, not a normal p.d.f
  8. I

    S1, how was it? My answers, please put yours to compare.

    The mean, median, quartiles and the interquartile range will ALL decrease by 5 minutes The standard deviation will stay the same. I'm pretty sure of my answer.
  9. I

    S1, post your doubts here....

    Yes, I got a very similar answer. But the slope is -0.015 (you missed a zero) and the y-intercept was 24.16 (difference of 0.02, doesn't matter anyways)
  10. I

    S1, post your doubts here....

    It's made up of three circles that don't meet, and the "bus" circle which joins them all. EDIT: for F: 9 in the F box, and 1 in the intersection between F and B H: 77 in the H box, and 33 in the intersection between H and B C: 64 in the C box, and 16 in the intersection between C and B
  11. I

    S1, how was it? My answers, please put yours to compare.

    I got the same results for 1 a and b. For d), I got t = 24.16 - 0.015h I got the same answers for question 2 Can't remember 3a and b, but I got the same answers for c, d, and e I got the same answers for 4a, can't remember the rest Q5:a) a = 0.1, b = 0.2 can't remember the rest of the question...
  12. I

    A level Biology: Post your doubts here!

    In short, vertical transmission is the transmission of genetic material from parents to offspring. So if a bacterium has, for example, an antibiotic-resistance gene, it can transfer this allele to its offspring by vertical transmission (or asexual reproduction) Horizontal transmission is when...
  13. I

    A level Biology: Post your doubts here!

    I don't take A2 Biology, I'm only sitting for the exams. Our school offers AP Biology, which is far more advanced then the A2 standard.
  14. I

    A level Biology: Post your doubts here!

    Divergence pretty much means the deviation from the original (i.e. how different the DNA is from the original sample). If a mutation is harmful, then it would shorten the lifespan of the organism, so he will not give the trait to his offspring. But if a mutation is harmless, then it wouldn't...
  15. I

    A level Biology: Post your doubts here!

    Non-cyclic photophosphorylation involves both light-harvesting clusters called photosystems (PS I and PS II). Light is first absorbed by the accessory pigments which transfer the energy to the reaction centre/primary pigment which is made from chlorophyll a. This excites electrons from PS II and...
  16. I

    'Physics Unit 6B: Experimental Physics' help needed for the written paper

    It really doesn't matter. But you must make sure that the numerator and denominator are BOTH in either millimeters OR micrometers (you can't have one in millimeters and the other in micrometers) So you will get a 66.7% uncertainty, which makes sense. I mean, you're measuring a 15 micrometer item...
  17. I

    A level Biology: Post your doubts here!

    They asked for a drawing, not a plan diagram, so you should draw as much as you can.
  18. I

    A level Biology: Post your doubts here!

    I would say that this is a very good drawing. The lines are generally drawn in an accurate way, but there is one striking error: Don't draw one line for two cell membranes. That is, each cell must have its own cell membrane border; don't use the same border and 'build up' on it to draw the...
  19. I

    A level Biology: Post your doubts here!

    I just had a look at the mark scheme. Quoting: "(0.3)7.5 and (0.2) 5 and (0.1)2.5" So I guess this means that 0.3% corresponds to 7.5 ml of R, and 0.2 --> 5, and 0.1--->2.5
  20. I

    A level Biology: Post your doubts here!

    According to the question: "You will need to make dilutions of the 0.4% solution of R, so that the concentration of R is reduced by 0.1% between each successive dilution. You will need 10 cm^3 of each concentration." So you will need to prepare 5 solutions of the following concentrations: 0.4%...
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