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i need some help with an as level biology (OCR) text book question watch

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    some scientists wanted to study the structure and functions of chloroplasts, they macerated some spinach leaves in a food blender, adding two percent sucrose solution and kept the mixture cold. they filtered the mixture to remove debris and then spun the mixture in a centrifuge, which speeds up the separation of the mixture and, after a short spin, the cell nuclei are pulled to the bottom of the tube, forming a sediment
    the supernatant liquid is then removed from the tube, placed in a nother centrifuge tube and spun again at a higher speed, the chloroplasts were seen at the bottom of the tube as a greed sediment.
    after decanting off the supernatant liquid, the chloroplasts were re-suspended in ice cold two percent sucrose solution before being used for investigations.
    a) suggest why the first organelles to sediment out during centrifugation were the nuclei
    b) suggest why chloroplasts were the second type of organelles to sediment out by centrifugation
    c) explain why leaves were used as a source of chloroplasts
    d) suggest why, prior to their use, the isolated chloroplasts were:
    (i) suspended in two percent sucrose solution
    (ii) kept ice cold
    e) name the substance which gives the chloroplasts their green colour
    f) briefly outline the function of the chloroplasts
    sorry about how long the question is guys im really struggling, thank you to everyone that replies! x
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    (Original post by yasemin1999)
    some scientists wanted to study the structure and functions of chloroplasts, they macerated some spinach leaves in a food blender, adding two percent sucrose solution and kept the mixture cold. they filtered the mixture to remove debris and then spun the mixture in a centrifuge, which speeds up the separation of the mixture and, after a short spin, the cell nuclei are pulled to the bottom of the tube, forming a sediment
    the supernatant liquid is then removed from the tube, placed in a nother centrifuge tube and spun again at a higher speed, the chloroplasts were seen at the bottom of the tube as a greed sediment.
    after decanting off the supernatant liquid, the chloroplasts were re-suspended in ice cold two percent sucrose solution before being used for investigations.
    a) suggest why the first organelles to sediment out during centrifugation were the nuclei
    b) suggest why chloroplasts were the second type of organelles to sediment out by centrifugation
    c) explain why leaves were used as a source of chloroplasts
    d) suggest why, prior to their use, the isolated chloroplasts were:
    (i) suspended in two percent sucrose solution
    (ii) kept ice cold
    e) name the substance which gives the chloroplasts their green colour
    f) briefly outline the function of the chloroplasts
    sorry about how long the question is guys im really struggling, thank you to everyone that replies! x
    a) Since the nuclei are the heaviest organelles.
    b) Since chloroplasts are the next heaviest organelles
    c) Chloroplasts are used to convert light energy into sugars in plants. Therefore, leaves are sure to contain them.
    d) I think that is to prevent the liquid from mixing together, meaning you end up with everything that is denser (like the nuclei), at the bottom.
    ii) It is kept ice cold to reduce kinetic energy and the rate at which enzymes break down organelles.
    e) The green pigment chlorophyll.
    f) Chloroplasts work to convert light energy of the Sun into sugars that can be used by cells. The entire process is called photosynthesis and it all depends on the little green chlorophyll molecules in each chloroplast.

    I hope this helps
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    thank you so so so so much!! :')
 
 
 
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