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    (Original post by brodingoson)
    The question asked why doesn't erythrocytes use oxygen when transporting it, so i put...

    oxygen can only dissociate from the iron ions/haemoglobin sub-units when the haemoglobin is in acidic conditions which only occurs when carbon dioxide enters and causes the reactions with water etc. and the H+ ions diffusing back in, alternating the tertiary structure of haemolgobin (due to the low pH) in which oxygen is then released...
    So basically erythrocytes could not even use oxygen in the first place when carrying it due to low co2 and if they could use it, they'd only be able to use it when it disassociates to respiring tissues

    But i dunno, you're right as well but erythrocytes in fact they actually do use a fraction of the oxygen they carry, but very minuscule

    That's the problem with breadth is that you could say loads for the answer in which all answers would be valid, but they won't accept it
    (kinda rambled lol)
    I think I put that erythrocytes don't need to use any ATP since they don't undergo any active processes like exocytosis, active transport etc since they rely on affinity and diffusion to carry out their function properly; hence they don't need any oxygen for aerobic respiration (which produces ATP).
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    Anyone got an unofficial mark scheme?
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    For the zoo question, I said providing medications (ex-situ approach) to prevent the endangered animals from suffering from any illness which may contribute to the death of the species. Is that wrong? That's the first thing that came into my mind when reading it.

    For the question saying ''Referring to the features of blood or whatever, explain why red blood cells needs to take blood to the capillaries'' or something related to that I said capillaries are one cell thick that contains endothelium, meaning that the diffusion distance is reduced. Is that enough for 2 marks?

    For the 2 marker on ''Explain/Give two reasons why species become critically endangered''' I said;
    -They do not become adapted to their environment and overcome selective pressure so the species cannot interbreed and pass on their beneficial characteristics to their offspring, and also they do not have sufficient features, such as their size, which places them into a disadvantage. Do you think I'll get 2 marks?

    For the question that said ''Explain an advantage of binomial classification'' I said it is universal, so scientists abroad can communicate worldwide to avoid confusion when classifying organisms

    The 3 marker about DNA; I said ''The complementary base pairs (Adenine attaching to thymine, cytosine attaches to guanine, form a double helix which are attracted together by hydrogen bonding, hence they are anti-parallel in which they are attracted in opposite direction of 5' and 3'

    Joining molecules was condensation reaction, but what was the chemical where two nucleotides attach together? I said RNA/nucleic acid? Maybe that's wrong?

    For the advantage/ disadvantage of red blood cells I put:
    Advantage; No nucleus means more space/ larger surface area for the red blood cell to transport oxygen, reducing diffusion distance
    Disadvantage; Cannot control/transmit information? Maybe that's too vague?
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    (Original post by melissa-23)
    what did everyone say for the question that was like 'why don't erythrocytes make oxygen' something like that
    eythrocytes have no organelles therefore no mitchondria so no respiration takes place so no oxygen is needed
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    (Original post by Simbak6)
    eythrocytes have no organelles therefore no mitchondria so no respiration takes place so no oxygen is needed
    I put that too
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    what did you all put for the very last question?
    about translocation i think because some people from my class talked about sucrose loading some talked about source and sink and a few talked about pressure gradient
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    (Original post by maxross)
    Was this the 'why don't erythrocytes use the oxygen they carry question?'
    I didn't really have a clue about it, but put something about they undergo very little metabolic processes and therefore don't require any energy, don't need to aerobically respire, so don't need oxygen.

    May be well off though! Anyone else got more of an idea?
    I think that's right. The Breadth paper don't tend to ask incredibly in depth questions so I can't see them wanting anything more than just that.
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    (Original post by oni176)
    For the zoo question, I said providing medications (ex-situ approach) to prevent the endangered animals from suffering from any illness which may contribute to the death of the species. Is that wrong? That's the first thing that came into my mind when reading it.

    For the question saying ''Referring to the features of blood or whatever, explain why red blood cells needs to take blood to the capillaries'' or something related to that I said capillaries are one cell thick that contains endothelium, meaning that the diffusion distance is reduced. Is that enough for 2 marks?

    For the 2 marker on ''Explain/Give two reasons why species become critically endangered''' I said;
    -They do not become adapted to their environment and overcome selective pressure so the species cannot interbreed and pass on their beneficial characteristics to their offspring, and also they do not have sufficient features, such as their size, which places them into a disadvantage. Do you think I'll get 2 marks?

    For the question that said ''Explain an advantage of binomial classification'' I said it is universal, so scientists abroad can communicate worldwide to avoid confusion when classifying organisms

    The 3 marker about DNA; I said ''The complementary base pairs (Adenine attaching to thymine, cytosine attaches to guanine, form a double helix which are attracted together by hydrogen bonding, hence they are anti-parallel in which they are attracted in opposite direction of 5' and 3'

    Joining molecules was condensation reaction, but what was the chemical where two nucleotides attach together? I said RNA/nucleic acid? Maybe that's wrong?

    For the advantage/ disadvantage of red blood cells I put:
    Advantage; No nucleus means more space/ larger surface area for the red blood cell to transport oxygen, reducing diffusion distance
    Disadvantage; Cannot control/transmit information? Maybe that's too vague?
    For the question saying ''Referring to the features of blood or whatever, explain why red blood cells needs to take blood to the capillaries'' or something related to that I said capillaries are one cell thick that contains endothelium, meaning that the diffusion distance is reduced. Is that enough for 2 marks?

    is this the question that talked about why blood dosent leave vessels until it gets to capillaries if so i put that capillary walls are are only made of endothelium with gaps (fenestrations) between the cells and that arteries and arterioles have outer layers
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    I tried to relate that question to the pO2 as at the capillary bed where the tissues are respiring more it is much less than when travelling through the major vessels..no clue if that's credit worthy though
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    (Original post by oni176)

    Joining molecules was condensation reaction, but what was the chemical where two nucleotides attach together? I said RNA/nucleic acid? Maybe that's wrong?
    I think that was just water after the condensation reaction
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    (Original post by SolomonP)
    I tried to relate that question to the pO2 as at the capillary bed where the tissues are respiring more it is much less than when travelling through the major vessels..no clue if that's credit worthy though
    which question did you relate to pO2
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    The one on why rbcs don't unload until at capillaries
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    (Original post by SolomonP)
    I think that was just water after the condensation reaction
    yeah pretty much for AS biology all condensation reactions lose a water molecule particularly for biological reactions
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    Does anyone have the locked specimen papers for depth in biology?

    Also, for evolution, how much of a focus should be put on Wallace?
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    (Original post by medicapplicant)
    For the question saying ''Referring to the features of blood or whatever, explain why red blood cells needs to take blood to the capillaries'' or something related to that I said capillaries are one cell thick that contains endothelium, meaning that the diffusion distance is reduced. Is that enough for 2 marks?

    is this the question that talked about why blood dosent leave vessels until it gets to capillaries if so i put that capillary walls are are only made of endothelium with gaps (fenestrations) between the cells and that arteries and arterioles have outer layers
    Yeah that was the question. It said ''by referring to blood vessels' functions'' or something like that so I just described capillaries and explained its function by stating they reduce the diffusion distance. It sound appropriate though but I am not sure what examiners will be looking for.
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    (Original post by SGHD26716)
    Does anyone have the locked specimen papers for depth in biology?

    Also, for evolution, how much of a focus should be put on Wallace?
    i think i put might have them ill have a look and pm them if i do and not much focus in the ocr book it just mentions that wallace independently came up with the same conclusion to darwin and that they released joint papers on evolution by natural selection.
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    (Original post by Jitesh)
    yeah pretty much for AS biology all condensation reactions lose a water molecule particularly for biological reactions
    I know condensation reaction releases water
    I said it ATP instead of water
    Am i wrong?
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    (Original post by brodingoson)
    I know condensation reaction releases water
    I said it ATP instead of water
    Am i wrong?
    Unfortunately I think so
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    (Original post by SolomonP)
    Unfortunately I think so
    Water is wrong as well, looked up the question...
    "however, the molecule that is released is not water but pyrophosphate"

    Knew it was something like pyrophosphate :/

    If people don't know what Q i'm referring to; pyrophosphate is a stable molecule released when 2 polynucleotides condensate
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    See for yourself: https://teaching.ncl.ac.uk/bms/wiki/...hodiester_bond
 
 
 
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