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  1. Z

    Biology P4 random notes

    First of all, both of them are steroid hormones. Both of them help increase the thickness of the endometrium and maintain the endometrium for embryo implntation However, estrogen is secreted by granulosa cells of a follicle while progesterone is secreted by luteal cells of the corpus luteum...
  2. Z

    Chemistry paper 42 may/june 11

    okay guys, lemme try to give a ridiculous explanation. Suppose E value is how accurately you can kick a ball into the goal post. Concentration is how many people there are who want to kick the ball. If there are many people to kick to the ball, despite your highest accuracy in kicking the ball...
  3. Z

    Biology P4 random notes

    Role of genetic counsellor: (from mark scheme) The goals of genetic counseling are to increase understanding of genetic diseases, discuss disease management options, and explain the risks and benefits of testing. Counseling sessions focus on giving vital, unbiased information and non-directive...
  4. Z

    Biology P4 random notes

    Plant growth regulators are basically plant hormones. We need to know about three plant hormones: (i) Auxin (specifically IAA) (ii) Gibberellic acid (GA) (iii) Abscissic acid (very confusing spelling) (i) Auxin There are several chemicals known as auxins, in our case it is IAA. Auxins are...
  5. Z

    Biology A2 Paper 4 Thread (1st June 2011)

    Also, for the Khan academy folks, why is the electrotonic potential slower than the action potential?? Please explain the reasons put forward by Sal
  6. Z

    Biology P4 random notes

    VNTRs: -Although the introns may seem useless, it has been found that they contain repeated sequences of base pairs. These sequences, called VNTRs, can contain anywhere from twenty to one hundred base pairs -A given persons VNTR comes from the genetic information donated by his or her parents...
  7. Z

    Biology P4 random notes

    Current treatment for CF: -Physiotherapy to dislodge mucus from the lungs -Antibiotics to fight infection -DNAse drug to loosen the mucus -Enzymes to help food digestion -Heart-lung transplant Importantly, all of these treatments address the symptoms, not the cause!
  8. Z

    Biology A2 Paper 4 Thread (1st June 2011)

    Isn't an ion channel not supposed to use ATP in transportation?? I thought only carrier proteins used ATP! But on reading that CFTR is a chloride channel that actively transports Cl- ions, I am not sure any longer! Please address my confusion guys!
  9. Z

    Biology P4 random notes

    Promoters: In prokaryotes, base sequences called promoters are situated just before each gene. These identify the point at which transcription should begin. In order for the transcription to take place, the enzyme that synthesizes RNA, RNA polymerase, must ATTACH TO THE DNA NEAR THE GENE...
  10. Z

    Biology P4 random notes

    Awesome! Had been looking for the ecological role for some time!
  11. Z

    Chemistry paper 42 may/june 11

    One problem of PCR is having a pure enough sample of DNA to start with. Any unnecessary fragment will also will also be amplified if we carried out PCR first. By the way, can't we increase the amount of DNA after we have obtained the required fragment?
  12. Z

    Chemistry paper 42 may/june 11

    This thing is debatable I guess. If we amplified the whole of the DNA sample, you would be amplifying the unnecessary fragments as well. If we then obtained restriction fragments using restriction enzymes, the extraction would be a headache I guess. I think it would be better, as the...
  13. Z

    Biology P4 random notes

    DNA probes: -A DNA probe is a small fragment of nucleic acid that is labelled with an enzyme or a radioactive tag or a fluorescent dye tag -It allows the identification of a specific sequence of nucleotides called the target DNA -The probe will bind to a complementary DNA sequence by base...
  14. Z

    Biology P4 random notes

    Botanic gardens: -Endangered plant species can be grown in botanic gardens -SEEDS or CUTTINGS collected (not the whole plant itself, lol) from species in the wild and then used to build up a population of plants Advantages: -Possible to create ideal growing conditions-either outdoors or in...
  15. Z

    Biology A2 Paper 4 Thread (1st June 2011)

    what is the ECOLOGICAL importance of biodiversity? Need some explanation of nutrient cycling in this context
  16. Z

    Biology A2 Paper 4 Thread (1st June 2011)

    I too am not sure if we do not require DCT. Preparing notes would be the safer thing I guess. About glomerulus, the diagram did help a bit. However, do you have a diagram that shows the podocytes, endothelial cells of the capillaries, epithelial cells of the capsule TOGETHER ?? That would...
  17. Z

    Biology A2 Paper 4 Thread (1st June 2011)

    Also, for the Khan academy folks, why is the electrotonic potential slower than the action potential?? Please explain the reasons put forward by Sal
  18. Z

    Biology P4 random notes

    Sympatric speciation, not many questions about this in exams yet, so wanted to explore it: It is due to reproductive isolation Some barrier of gene flow occurs between individuals in the same geographical area resulting from different behaviours. The members of the same species may occupy...
  19. Z

    Biology A2 Paper 4 Thread (1st June 2011)

    The book is what confused me. As I have understood it, the capillary and basement membrane surrounded by podocytes are themselves surrounded by a renal lumen. The renal capsule encloses the lumen. So, if the podocytes form the wall as well, we would require another layer of that.
  20. Z

    Biology A2 Paper 4 Thread (1st June 2011)

    how many layers of podocytes are there?? From what I understand , podocytes wrap around the basement memabrane surrounding the capillaries of the glomerulus. But now I read that podocytes form the wall of the renal capsule too. So, are there two layers of basement membrane and two layers of...
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