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  1. 6

    A level Biology: Post your doubts here!

    probe to determine position agarose for seperation and median
  2. 6

    Total Resistance ??

    uhm if you redraw the circuit its basically 3 resistors in parallel
  3. 6

    Total Resistance ??

    6/11? Havent done these in so long
  4. 6

    A level Biology: Post your doubts here!

    T-lymphocytes is the only one that reacts to organ transplants, and they flow freely around the body. so D correct C is wrong because T cells do not release antibodies, even T helper cells only aid B cells on antibody production B is wrong because T cells do not release antibodies. A is wrong...
  5. 6

    A level Biology: Post your doubts here!

    you measure the closest distance from the inner alveolar wall to the membrane of the red blood cell, which is roughly 6-8mm depending on where you measure magnification is x2500 so 6mm or 8mm divide by 2500 = 2.4 or 3.2 micrometers so answer is B and solute potential of cells in phloem sieve...
  6. 6

    you measure the closest distance from the inner alveolar wall to the membrane of the red blood...

    you measure the closest distance from the inner alveolar wall to the membrane of the red blood cell, which is roughly 6-8mm depending on where you measure magnification is x2500 so 6mm or 8mm divide by 2500 = 2.4 or 3.2 micrometers so answer is B
  7. 6

    A level Biology: Post your doubts here!

    1. is correct because limited nitrogen compound = limited number of producers = limited number of energy available to consumers 2. is wrong, it's never good to change an ecosystem with external factors. If you add excess nitrate compounds, this will cause eutrophication causing algae bloom...
  8. 6

    AS Biology P1 MCQs Preparation Thread

    DNA is semi conservative replication, DNA has 2 strands at the start it is all made of 15N. so 15N - 15N DNA it grows replicate under 14N so all 15N will pair with a 14N so 15N-14N DNA with a overall weight of 14.5, this is lighter so this is at Y after centrifuge. and for next generation...
  9. 6

    A level Biology: Post your doubts here!

    #12 #12 change in pH changes H+ ion concentration H+ ion concentration only affects ionic and hydrogen bonds. alpha helix secondary structure is held by hydrgoen bonds so all correct except fact 1 #13 3 is wrong because warm water does not dissolve more oxygen this is A2 chem so you kinda...
  10. 6

    A level Biology: Post your doubts here!

    its a niche, because all of these applies to the roles of the tree. yeah this is ******* stupid, but from my definition its a niche. I'll give you a direct quote from the 2013 CIE endorsed textbook. I'll colour label the same facts textbook: The niche of an organism is its role in the...
  11. 6

    A level Biology: Post your doubts here!

    that is very weird, I just double checked with CIE endorsed textbook 2013 third edition as well as the encyclopedia nitrogen fixation in soil requires supply of hydrogen, supply of ATP, anaerobic conditions ONLY nitrogen fixation in the atmosphere which is caused by lightning which directly...
  12. 6

    A level Biology: Post your doubts here!

    #27 uhm you kind of have to read this yourself, specify your question abit more and I might be able to help you. #32 haemoglobin only binds with O2, CO, H+, does not bind with HCO3-, so #4 is immediately wrong. the affinity is CO>H+>O2. so CO and H+ will displace O2 from oxyhaemoglobin. #33...
  13. 6

    A level Biology: Post your doubts here!

    do you want me to explain why each one is the answer or why the other options are wrong?
  14. 6

    A level Biology: Post your doubts here!

    the only method for a plant to produce energy is photosynthesis, so energy for growth, respiratory heat loss, other life process all came from photosynthesis, hence you add all of them. same goes for next question, the 27000 is energy plant can provide to herbivore (energy used in growth), the...
  15. 6

    AS Biology P1 MCQs Preparation Thread

    no, at prophase the chromosomes coil up and at the end of telophase they uncoil to get ready to be replicated via semi conservative replication in interphase (which is not part of mitotic cycle)
  16. 6

    AS Biology P1 MCQs Preparation Thread

    firstly question states its either anaphase or metaphase metaphase is when the chromosomes line up at equator ie. not separated anaphase is when its separated to chromatids in the picture they're not separated so it must be metaphase
  17. 6

    AS Biology P1 MCQs Preparation Thread

    its 3.14*125*125=4.9*10^4 the radius is 50 small divisions and we know that 40 small divisions = 0.1mm or 100micrometers each small division is therefore 100/40 = 2.5 micrometers radius is thus 50x2.5= 125 micrometers area = pi x ( radius squared)
  18. 6

    AS Biology P1 MCQs Preparation Thread

    #18 answer is A because mitosis is a form of asexual reproduction characteristics: daughter cell and parent cells are identical ie. same jobs, DNA unchanged so B,C,D is all correct and semi conservative replication occurs before mitosis during interphase so A is wrong #40 we find the energy...
  19. 6

    A level Biology: Post your doubts here!

    yes there are lots of flaws in the multiple choice paper, you just have to pick the most appropriate answer or rely on your own practical experiences. In most cells and in general, mitochondria should not be seen, and lysosome is never seen. I'll do a short summary for you, basicaly from the...
  20. 6

    A level Biology: Post your doubts here!

    #21 definition of gene is a sequence of DNA on a section of chromosome that has some function ie. making polypeptide chains via mRNA production B is a description of DNA or a segment of chromosome not gene #23 A is correct because they showed that both CUG and UUA code for the same amino acid...
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