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    Okay guys, let's go through the spec. now.

    Structure and function of chloroplast in photosynthesis. Stroma contains enzymes for calvin cycle, thylakoid membranes contain chlorophyll, photosystems and electron carriers. They are folded into grana which give them a high surface area for maximum absorption of light. What else?
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    Outer & Inner membrane keep reactants near reaction sites, different variations of chlorophyll that absorb at different parts of the spectrum so + light can be used, large SA is also useful for enzyme controlled reactions ...
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    (Original post by Nereis)
    Me too Hate how it can be synoptic. Atleast I resat unit 2 so have some synoptic knowledge, but don't stand a chance if it's unit 1 stuff.



    ???
    Oh, don't worry about it! Cell mediated immune response is just the name of the process that T Killer cells are involved in. In this response, ACTUAL INFECTED CELLS are killed by T Killers hence the name CELL mediated.

    In humoral response, FLUIDS are involved [the term 'humoral' is related to 'fluids'. B Cells, plasma cells/B effector cells are involved in this. It's when immunoglobulins/antibodies are made. The anitbodies are in the plasma and it's 'fluid'. Nothing too specific or new, so don't worry.
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    Are you all learning equations for photlysis?

    The best one for me is: H20 ---> 2e- + 2H+ + 1/2O2

    I don't really remember the OH splitting at all.
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    OHH okay I feel better now

    Thylakoids are made up of membranes, contains pigment/chlorophyll - was worth a mark in Jan paper.
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    Hydroxide ions are the source of electron (& O2)
    2OH ---> 2OH + 2e-
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    But how do you explain H+ ions and O2 formation with that equation?

    H2O -> 2e- + 2H+ + 1/2O2 is kinda better?
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    You can't that why its better to give the equation you've stated (because it shows the source of electrons, hydrogen ions & oxygen is water). But DO state that the real source of electron & oxygen is OH (just in case)!
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    4OH- --> 4OH + 4e-

    4OH --> 2H2O + O2

    That's the only other way I know lol.
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    T-Killer cells attack infected body cells, B cells bind with the actual bacteria, is this correct? Do B lymphocytes work in the same way against virus cells?
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    Yea, viruses have antigens and B Cells can bind to them I guess and make antibodies. But viruses usually infect body cells and in this way, B Cells cannot fight the virus. T Killer cells can though.
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    @ Doughboy :eek: it would be easier to use the water eqn (but nice manipulation of the two equations :yes:)

    @ Nereis
    T killer cell attach to antigens on a pathogen infected cells & kill the cell.
    B (plasma cells) - secrete antibodies specific to the antigen.
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    T-Killer cells attack infected body cells, B cells bind with the actual bacteria, is this correct? Do B lymphocytes work in the same way against virus cells?


    B cells engulf bacteria by endocytosis and absorbe the antigens becoming APCs.
    The T helper cell then binds to the B cell and releases cytochromes (I think) causing the B cell to clone and then differentiate into plasma cells and release antibodies...

    With viruses...
    A body cell engulfs a virus and becomes an APC itself.
    A T killer cell with CD4 receptors binds onto the body cell and releases enzymes to destroy the cell..

    Probably forgot something or went wrong somewhere..
    Damn exam..

    Though on a side note.. anyone else think C3 went really really well today?


    EDIT: Seems this has already been answered ¬_¬
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    Perfect, thankyou for your help.

    I think post-transcriptional changes could come up, not mentioned in Jan exam and a small part of the book. We all know how edexcel like to ask us about tiny parts of the book.
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    B Cells can still make antibodies specific to the virus I think.

    EDIT:

    Post-Transcriptional Modification of mRNA:

    DNA/genes contain both non-coding and coding sections. The non-coding sections are called introns and are known as 'junk DNA' and do not code for any amino acids. The coding sections are called exons and these code for amino acids.

    When mRNA is transcribed from DNA, both exons and introns are copied. This is called pre-mRNA

    [NOTE: Does post-trans. changes occur in nucleus or cytoplasm? I vaguely remember cytoplasm?]

    Anyway, the mRNA containing both exons and introns leave the nucleus through the nuclear pore and undergoes post-trans. changes. The mRNA is spliced using enzymes and introns are removed from the mRNA. Mature mRNA is formed and this now contains strictly exons which code for an amino acid sequence. Before the enzymes join together the spliced mRNA pieces, the exons can be rearranged in a variety of ways. In this way, different sequences of amino acids/bases can obtained and so one gene can give rise to several proteins.

    LOL
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    (Original post by Doughboy)
    B Cells can still make antibodies specific to the virus I think.
    You're probably right..

    But also remember interferons (non-specific) against viruses!

    Can someone give me the major steps of the using antibodies against bacteria practical.. Can't find it..

    Thanks
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    Interferons interrupt protein synthesis in viruses, yes? So can't do anything to bacteria?

    Also, there's a fair bit about how HIV damages CD4 sells eg. glycoproteins bind with cd4 receptors on t-lymphocytes, viral rna enters cells, uses reverse transcriptase etc. Is there much about how the tb virus affects cells?
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    (Original post by Doughboy)

    [NOTE: Does post-trans. changes occur in nucleus or cytoplasm? I vaguely remember cytoplasm?]

    I do believe in the nucleus.. Think of it like this..
    Exons: Exit nucleus.
    Introns: Stay in nucleus.
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    Antibiotics practical:
    1) mention a nutrietn agar plate
    2) mention spreading a lawn of bacteria onto the plate using an innoculation loop
    3) mention the antibiotic solutions, maybe a range of concentrations?
    4) paper discs or wells placed onto the lawn of bacteria
    5) sealed plate/dish
    6) incubate below 30 degree or at 30 degrees I can't remember. But it has to be below body temperature
    7) mention some safety aspect or antiseptic technique or a control

    Antiseptic techniques include sterilizing equipment using Bunsen flame and ethanol.

    ==

    Interferons are also involved in promoting other immune responses (including non-specific such as inflammation and specific).

    ==

    Guys, what is the evidence for an evolutionary race? What are the adaptations of HIV and Mycobacterium to evade immune system?
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    (Original post by HyperNova)
    You're probably right..

    But also remember interferons (non-specific) against viruses!

    Can someone give me the major steps of the using antibodies against bacteria practical.. Can't find it..

    Thanks
    Assuming you mean testing antibiotics? Seem to be certain key things to be included when I've looked at markschemes:

    Antibiotic should be placed on an agar plate seeded with bacteria/agar with bacteria lawn/eq., using filter discs or in wells, etc.
    Use aseptic technique eg. sterilise equipment, do not fully seal the petri dish
    Incubate at 25C
    For 24 hourse
    Examine agar for inhibition zones - clear area
    Clear areas mean that antibiotic prevented bacteria growth, bigger the area, better the antibiotic (apparently we have to state the obvious)
    Compare to a control - no antibiotic


    Wantttt this question to come up. Nice easy 5 marks.
 
 
 
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