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    Hi, the syllabse says
    "understand the need for the detection of external stimuli; the
    concept of sensory receptors, illustrated by the detection of light
    in flowering plants by phytochrome pigments and in animals by
    the retinal pigments in the mammalian eye
    ."

    So do we just need to know about idoposin and rhodopsin etc, and not the structure of the eye, i.e knowing how to label the eye and fuctions and compostion of the layers of the eye?

    thanks :tsr:
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    Yep I think its just the pigments and rods & cones. In the NAS book the structure of the eye is in the 'background' section so I would say we don't need to know the eye structure.
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    kool, thanks a lot, that saves me a lot of time.
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    hi but ive seen in one of the unit 4 past paper that they ask question about where the eye pigments are found in the eye, so basically you need to know something about fovia and the fluids in the eye, aqueous and humor fluids.
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    What like this stuff..

    two types of receptor cells:

    a) the rods - these are sensitive to light intensity and black and white these are evenly distributed throughout the retina except the fovea.

    b) the cones - these are sensitive to wavelength ie. colour. These are greatest concentrated in the fovea where the cells are longer and thinner meaning you can get a higher concetration per unit cell.
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    The rods.

    The outer segment is the photo sensitive region, consists of a large number of disc shaped membrane vesicles called lamellae which contain the photo sensitive pigment Rhodopsin

    the Rhodopsin consists of Opsin - a protein and Retine - derivation of vitamin A.

    This consists in two isomers Cis and Trans

    When light strikes it is converted from Cis to Trans. This causes it to split and is known as bleaching.
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    i think i've doen a past question where we had to label parts of the eye...but it was abit ancient so maybe it was pre 2000
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    I do human biology so I dont know if what i learn is differant from the biologist. But unit 4 in January for me had an extended prose which was describe the roles of pigments in the mammalian eye.
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    yeh you have to know about the rod cells and cone cells but im saying is one of the question ive seen on a past unit 4 paper had an eye structure which has questions underneath asking about what 2 fluids are found in the eye, plus there are question of phytochromes even for human biologist about the pf pfr. Also need to know something about bipolar or sharing or same ganglieon by rod cells which has converging pathways where as cone cells has its own ganglieon and one cone cell conducts 1 impulse unlike rod cells where several conducts 1 impulse.
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    photochrome is that blue-green pigment in plants right?

    Where is can be either P660 which absorbs red light or
    P730 which absorbs far red light

    And if each absorbs light it is converted to the other.

    Fluids in the eye?!
    what fluids are these?
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    it the aqueous humor and vitreous humor both found in the eye. well just keep it in mind it might pop up in the exam or it might not, but its always better to know it. good luck
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    Ah! I know those two now lol

    I hope the eye dont pop up id rather neurones do.

    Good luck on your exams too and i hope you havent got to many left.
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    u know i would play it safe and learn everything.
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    ive still got A2 BIOLOGY 4,5 AND CHEMISTRY 4,5,6 LEFT SO HOPEFULLY WILL DO ALRIGHT IN IT. THANKS
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    the eye structure is easy anyway, we have been doing it from lower years so it doesn't waste any time to learn,well for me anyway.
    And the syllabus is just rough guideline, they might put stuff in questions which is not exactly mentioned on syllabus, i've learnt this in past bio exams
 
 
 
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