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OCR Biology F212 Revision [3rd June 2013] (Now Closed) Watch

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    (Original post by YaprakDokumu)
    For the question about the pathogen, didn't you have to talk about lymphocytes because they also help destroy the pathogen (killer T cells). I wrote nothing about the process of phagocytosis, but wrote about antigen presenting and clonal expansion and differentiation and what they all do and so on........ please anyone??
    The question asked how pathogens are destroyed after binding to the phagocyte.

    As I've said previously in the thread, I think the majority of the marks are for phagocytosis. But then again you're correct in saying T-killer cells and antibodies do help destroy pathogens.

    Perhaps a mixture of the two would be correct, but not sure you'd get all of the marks for just talking about lymphocytes.
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    (Original post by Saif95)
    NOOO!

    How many decimal places was it?
    4
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    (Original post by Kayess67)
    The differentiation of T-killer cells and lymphocytes does destroy pathogens and does happen after the pathogen has bound to the phagocyte. I can't remember the exact question, but I included phagocytosis and lymphocytes etc. I hope both are creditworthy!!

    i hope so, because logically, it should get us marks because they do destroy the pathogen
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    For the collagen question, the 6 marker I included;
    3 polypeptide chains
    triple helix
    Hydrogen bonds
    every 3rd amino acid = glycine = small so strands lie close together
    lysine of R group bonds with adjacent chains

    How many would I get for this?
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    (Original post by Saif95)
    NOOO!

    How many decimal places was it?
    Personally I just used the same amount of decimal places as the answer that was already in the table. Believe this was 4 decimal places.

    When it came to my calculations I don't think I came across a number with more than four decimal places. And for those that were less I just added zeros on the end.
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    (Original post by krishkmistry)
    Haha well I've just checked it and they accepted it so il be fine


    Posted from TSR Mobile
    i said droplets and exchange of fliuds?
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    For the question on how phylogeny is related to classification

    -Phylogeny is the study of the evolutionary history of an organism. This allows us to know how closely different species are related and if they have a common ancestor. This allows us to group organisms with a common ancestor into the same groups.

    How many marks out of 3 is this answer?
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    What did everyone get for the Simpsons Index of Diversity one?
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    (Original post by MarkProbio)
    The question asked how pathogens are destroyed after binding to the phagocyte.

    As I've said previously in the thread, I think the majority of the marks are for phagocytosis. But then again you're correct in saying T-killer cells and antibodies do help destroy pathogens.

    Perhaps a mixture of the two would be correct, but not sure you'd get all of the marks for just talking about lymphocytes.

    ok thanks, I kind of mentioned about the phagocytes engulfing and digesting the pathogen
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    (Original post by 24hoursmiles)
    For the collagen question, the 6 marker I included;
    3 polypeptide chains
    triple helix
    Hydrogen bonds
    every 3rd amino acid = glycine = small so strands lie close together
    lysine of R group bonds with adjacent chains

    How many would I get for this?
    i think you get marks for saying the bonds such as hydrogen aa mark for covalent then a mark for 3 polypeptide chains then about how they are twisted(helix) but i dont know what else
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    (Original post by 24hoursmiles)
    What did everyone get for the Simpsons Index of Diversity one?
    0.6366 i think :P
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    (Original post by 24hoursmiles)
    What did everyone get for the Simpsons Index of Diversity one?
    For the figure or the explanation of a low Index? For the figure I got something like 0.6343, can't remember the exact figure.

    For the low Index, I put that it means the habitat has low biodiversity and any small changes may have a large impact on the whole habitat. The ecosystem may be dominated by one or a few organisms, hence any change will impact the entire food chain.
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    (Original post by Munrot07)
    0.6366 i think :P
    i got 0.6364
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    (Original post by MarkProbio)
    For the figure or the explanation of a low Index? For the figure I got something like 0.6343, can't remember the exact figure.

    For the low Index, I put that it means the habitat has low biodiversity and any small changes may have a large impact on the whole habitat. The ecosystem may be dominated by one or a few organisms, hence any change will impact the entire food chain.
    i said impact on food web,not enough food to or good conditions for the population to survive well,basicaly what you said all rounded up :P
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    (Original post by jackitsme)
    i got 0.6364
    did you round at any point?
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    (Original post by jackitsme)
    i got 0.6364

    i got 0.6366 :/
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    (Original post by Munrot07)
    0.6366 i think :P
    Me too
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    I got 0.6366

    Showed all my calculations then put to 3 sig figs so my answer was 0.637
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    So here's my interpretation of the paper for anyone who wants to read (maybe TLDR :P)

    Q1
    Name given to sequence of amino acids (1)
    I put primary structure

    Draw the structure of an amino acid (3)
    H2NCRHCOOH (drawn out)

    Why collagen is good for arteries (1)
    I put strong/tough to withstand high blood pressure, but i'm uncertain, flexibility probably would have been better.

    Describe the structure of collagen molecule (6)
    3 coiled polypeptide chains (quarternary structure) to form a rope
    Left hand helix shape
    Glycine is 1 in every 3 amino acids (smallest R group, close packing)
    Hydrogen bonds between polypeptides
    (now I'm not sure the next is right as it says the collagen molecule but I mentioned lysine's and covalent cross links
    I also said insoluble but I'm not sure thats part of structure,

    Q2
    Type of biological molecule (1)
    Enzyme

    Why can it catalyse both (3)
    I talked about enzyme active site specificity complimentary to substrate. Both molecules have similar shapes/bonds, basically same except 2 less Hydrogen and 1 Oxygen in the DHP (or w/e it was called) So ESC forms.

    Why high ethanol concentration decreases toxicity (3)
    I said they both compete for the active site, where ethanol is present it will enter and stop DHP from entering. So less DHP can be broken down in the same amount of time, so toxic products formed slower, so body can remove these before concentration increases too much.

    Q3
    Infective agent of TB (1)
    Mycobacterium tuberculosis

    How its transmitted (2)
    Exhaled droplets of moisture by infected person inhaled by uninfected people, through coughing, sneezing, laughing, talking (I think you could also mention cattle meat for M.Bovis)

    Describe the data between 2000 and 2008 (3)
    I said low income and middle low stay the same (figures)
    Medium upper increases I think it was and upper decreases
    Both years low is highest incidence, upper is lowest incidence]

    Why low income have greater incidence (3)
    More likely to have malnutrition
    Unable to afford vaccines/antibiotics or take antibiotics when needed
    Overcrowding and sleeping as cannot afford to buy separate houses

    Q4.
    Which cells are phagocytes? (1)
    I put just C although apparently B is too but it looks just as similar to a lymphocyte and a monocyte in my opinion so there should hopefully be allowance in the MS.

    Why "secondary"? (1)
    After primary defence breached, part of immune response to antigens

    Why "non-specific"? (1)
    Can attach to any foreign antigens

    What happens after pathogen attaches to phagocyte? (7)
    Engulfed, membrane infolds, phagocytosis, endocytosis
    Phagosome formed
    Lysosomes move towards and fuse with phagosome
    secrete hydrolytic enzymens/lysins
    break down/digest pathogen
    Into soluble products (e.g. amino acids)
    absorbed into cytoplasm
    waste excreted
    macrophages can become APC's

    Q5.

    Calculate SI of Diversity (3)
    I got 0.6 something

    Species richness (1)
    Number of species present in an area

    Species evenness (1)
    Relative numbers of individuals of each species present in an area

    Low SI Index (2)
    Low biodiversity suggests dominated by few species
    If environmental change, habitat cannot adapt, dependence on that species

    Improve accuracy of sampling (2)
    use random sampling, random coordinates generated by calculator
    Repeat at different times of month/year (I was thinking about selecting suitable quadrate size but chose the other)

    Q6.
    There's a 1 mark question here I can't quite remember, something about genetic variation I think (1)

    Why crop yield varies (2)
    I put insecticides used to stop disease spread, resistance to insecticides, use of fertilisers, climate change (temp/rainfall)

    How genetic variation arises (1)
    Mutation (i wondered if you could put sexual reproduction also)

    Selective breeding short term + long term (7)
    I said this is artificial selection
    Select wild varieties with resistance and cross breed
    prevent asexual reproduction
    Select offspring with resistance and highest yield
    Cross breed again
    repeated for many generations - this is all short term
    Then long term - mutations can cause pathogens to change
    Conserve wild plants, botanic gardens, seed banks, potential of alleles to other diseases
    Multiple alleles to provide better protection
    I also mentioned gene marking somewhere

    I have to admit this question threw me a bit though

    Q7.
    define biodiversity (2)
    Variety of life, range of living species, habitats and communities and the ecosystems of which they form a part
    Genetic variation within and between species

    Why conservation methods needed for the specific area (2)
    Important part of food chains
    Tourism, aesthetically pleasing ( I wonder if you could also put gene pool etc.)

    Suggest why people against culling (1)
    I said morally wrong, inhumane to trap and kill just to keep population down

    Why red squirrel population may be higher than counted (2)
    Grey squirrels not intimidated by humans, red hiding, not seen
    red have better camouflage for red trees, not seen (not sure this is right)

    EIA criteria (3) (did not like this one)
    Effect on biodiversity, environmental sensitivity due to noise pollution (wind turbines)
    whether there are any endangered species (e.g. red squirrel)
    Method to reduce impact (e.g. translocation of red squirrels)

    Q8.
    Components of DNA (2)
    Nitrogenous organic base (I put cytosine as well because it was next to G)
    Nucleotide

    Complete gaps (2)
    Polypeptide
    Ribosome

    How RNA would be different to DNA (2)
    RNA would be single stranded
    RNA would have U instead of T

    Why it is "semi-conservative" (2)
    2 DNA molecules produced, each has one old strand and 1 new strand forms by new nucleotides.

    Why complementary base-pairing is important (2)
    identical molecules of DNA are produced
    so exact protein is made
    purine to pyramidine
    Different base would be mutation, different protein

    Draw in the R1 and R2 (2)
    For R1 I did a line between the N15 line and the N14 line
    For R2 I did half a line at the same position as R1 and the other half at N14

    3 precaution in centrifugation (3)
    Same concentration of sugar solution
    Same volume of sugar solution
    Same time for centrifugation

    Q9
    Fill space (5)
    Whatever the genus was
    I think I got order
    I think I got phylum
    Kingdom = Animalia
    Domain = Eukaroyta

    Phylogeny (3)
    Study of evolutionary relationships, involves ancestral trees
    Classification, placing organisms in groups based on similarities (biochem/anatomy)
    Phlyogeny shows how recent is the common ancestor, more recent = more similarities
    therefore organism placed in similar groups
    less time for mutation/variations to arise

    Why water bear was undiscovered (2)
    Too small to be seen
    Microscopes were not available
    Also talked about speciation because it did say
    why were they not discovered "before 300 years" I think.

    Anyway, these are may answers, they may not necessarily be correct, just for people to make comparisons.
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    (Original post by niceguy95)
    I got 0.6366

    Showed all my calculations then put to 3 sig figs so my answer was 0.637
    ahh crap wait.....i got that! i got 0.3 something ending with 4 to get 0.6366
 
 
 
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