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    For the question regarding enzymes "S" and "T" or something. And they asked what their roles/function was....

    For that I was saying that these were the enzymes : Integrase and Reverse transcriptase. I was talking about their roles, how Reverse transcriptase reverses transcription, and changes Viral RNA into Viral DNA, and how integrase integrates the Viral DNA in the host's cell.

    Is this what we were supposed to do, or have I wrote BS?
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    (Original post by blue21)
    That sounds like a pretty good answer, it was just suggest so I'm hoping if we talked about any part of the cell membrane we will get the mark, I started rambling on about the phospholipid bi layer!

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    Yeah, they might allow for a range of answers, as long they make sense?
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    (Original post by Lgambo)
    Oh and why can't virus survive a cut in the skin?
    Inflammation
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    (Original post by SKK94)
    I said that too.
    I also mentioned that maybe the pH of the skin causes the protein coat to deform, hence the virus becomes inactive?
    Yeah, Good answer.
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    (Original post by Taylor Swift)
    Inflammation
    Surely it has to get past the skin for any inflammation to occur ?
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    Grade boundaries on this paper??? I think it was WAY harder than others ...
    I think I did really badly -.- (silly mistakes), need to really do well in unit 5! LOL
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    (Original post by C94)
    Surely it has to get past the skin for any inflammation to occur ?
    The first part was the skin has keratin protein which is hard, and this is seen as a physical barrier.

    The second part of why it can't enter cells was inflmmation.
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    (Original post by C94)
    Surely it has to get past the skin for any inflammation to occur ?
    There were two questions,
    Something like- why does the skin act as a barrier?
    And- if a virus was to get into a cut, why wouldn't the body be infected?
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    (Original post by Taylor Swift)
    The first part was the skin has keratin protein which is hard, and this is seen as a physical barrier.

    The second part of why it can't enter cells was inflmmation.
    Yes that part would be correct
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    (Original post by Lgambo)
    There were two questions,
    Something like- why does the skin act as a barrier?
    And- if a virus was to get into a cut, why wouldn't the body be infected?
    It was keratin/protein ... Hard skin - Physical barrier
    This was a question I saw from a past paper before!
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    (Original post by Taylor Swift)
    It was keratin/protein ... Hard skin - Physical barrier
    This was a question I saw from a past paper before!
    I also put that the skin flora would prevent the colonization of bacteria and viruses.
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    (Original post by SKK94)
    I said that too.
    I also mentioned that maybe the pH of the skin causes the protein coat to deform, hence the virus becomes inactive?
    :rolleyes: The skin acts as a physical barrier to the inside of the body, and skin flora (healthy bacteria on the skin) take up any space that otherwise pathogens would and the skin flora outcompete them.

    Also the common cold virus won't infect any cells inside the blood stream because 1) it binds to a specific protein receptor in cells in the nose - these receptors might not be present in the blood stream or surrounding tissues so the virus can't infect any cells, and 2) any macrophages present will recognise the virus particles as foreign and ingest them through phagocytosis.


    Honestly, I thought that was the easiest Biology 4 paper I've done out of the past papers. Definitely easier than January also. In recent years the grade boundaries have been highest of 67 for A*, but I can see it being 69-71 for an A* for this paper.

    I probably dropped 5 marks on virus question, as I was confused about S, T and U, but hopefully I picked up 1 or 2 marks each on these questions. On the other questions I probably dropped the odd 1 or 2 marks, I'm expecting 75+ on raw marks.

    Several of the questions seemed to be literally copied from other papers, e.g. the 'how cellulose is produced from the Calvin Cycle' question - I was revising that exact question the evening beforehand in a past paper. The question about reproductive isolation due to the behavioral differences of the chiffchaffs and worblers and their different mating songs - that was another question I've seen before.

    I was also suprised at the fact they missed out a lot of key topics. Photosynthesis wasn't covered in too much detail, there was nothing on succession if I remember correctly, or entomology, I can't remember that either. Couldn't believe the fact there was no 3-4 mark data analysis questions as well!

    Edit: Negging me? Because I found it easy? I'm allowed to find it easy, I wasn't being cocky or arrogant about it though! This was one of the easier papers in my opinion, sorry about that.
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    (Original post by C94)
    For the question regarding enzymes "S" and "T" or something. And they asked what their roles/function was....

    For that I was saying that these were the enzymes : Integrase and Reverse transcriptase. I was talking about their roles, how Reverse transcriptase reverses transcription, and changes Viral RNA into Viral DNA, and how integrase integrates the Viral DNA in the host's cell.

    Is this what we were supposed to do, or have I wrote BS?
    I'm also certain that S and T weren't reverse transcriptase and integrase. In the question it said that the RNA strand is inserted from the virus and it travels straight to the ribosome for translation - therefore reverse transcriptase and integrase wouldn't be required as they are only need for transcription of the viral DNA/RNA.

    Also the question before that said to compare the differences between the way HIV infects cells and copies it's RNA, compared to how the common cold virus did. The main difference was the fact that HIV, and not the common cold, required the use of reverse transcriptase and integrase.
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    (Original post by Qwob)
    I'm also certain that S and T weren't reverse transcriptase and integrase. In the question it said that the RNA strand is inserted from the virus and it travels straight to the ribosome for translation - therefore reverse transcriptase and integrase wouldn't be required as they are only need for transcription of the viral DNA/RNA.

    Also the question before that said to compare the differences between the way HIV infects cells and copies it's RNA, compared to how the common cold virus did. The main difference was the fact that HIV, and not the common cold, required the use of reverse transcriptase and integrase.
    If the enzymes were not reverse transcriptase and integrase, what could they have been then?
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    (Original post by C94)
    If the enzymes were not reverse transcriptase and integrase, what could they have been then?
    This is what confused me. I took a guess and made us some BS saying that it might be RNA polymerase to help synthesise more RNA strands, and said another enzyme might be help make the capsid, or proteins on the capsid. These were both guesses though, most likely incorrect, but there was no need for the virus to have reverse transcriptase or integrase. I've looked through my textbook as well and I can't find any mention of any other specific enzymes that a virus might produce.
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    (Original post by Qwob)
    This is what confused me. I took a guess and made us some BS saying that it might be RNA polymerase to help synthesise more RNA strands, and said another enzyme might be help make the capsid, or proteins on the capsid. These were both guesses though, most likely incorrect, but there was no need for the virus to have reverse transcriptase or integrase. I've looked through my textbook as well and I can't find any mention of any other specific enzymes that a virus might produce.
    Well, from what you are saying, RNA polymerase would be right.

    But I am pretty sure that the examiners were trying to make us think of Reverse Transcriptase and Integrase. Unless it was a trick question :/

    Anyone else got any input on this question??
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    (Original post by C94)
    I put about skin being impenetrable, and that the skin was made of skin.
    It formed a tough barrier.

    No idea if it is right though.
    Yh that's what I said and that its made of keratin? I've no idea...
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    (Original post by HQazi)
    Yh that's what I said and that its made of keratin? I've no idea...
    Lol just noticed, that I have said that the "skin was made of skin". I meant keratin.
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    Well sh*t, that was a weird paper
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    For the skin one I wrote about the physical barrier of epithelial cells and the glands of sebum and other fatty acids on the skin which destroy bacteria. Hoping this is right :/
 
 
 
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