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Biology for Advanced Level Secondary Schools

           cellular membranes. It occurs in all cells,  flattened, plate-like,  compartments  or
           except  in  the  prokaryotic  cells  and  in  cisternae  (Figure  1.16).  It  is  a  modified
           cells of certain eukaryotes, such as fungi   smooth endoplasmic  reticulum.  The
           and bryophytes. It also does not occur     Golgi apparatus is associated with small,
           in cells of mature sieve tubes of plants,   spherical sac-like structures called Golgi
           spermatozoa, and in red blood cells.       vesicles. These contain various secretions
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                                                      such as hormones, mucus or enzymes, and
           Structure of the Golgi bodies              they are future lysosomes.
           It is disc-shaped;  consisting of central,







                             Incoming
                       transport vesicle


                             Cisternae





                               Lumen
                     Secretory vesicle


                        Newly forming
                               vesicle


                                       Figure 1.16: Structure of the Golgi apparatus

           Functions of the Golgi bodies              Cytoskeleton
           The functions of Golgi bodies include the   A cytoskeleton is a complex network of
           following:                                 protein filaments and microtubules which
            (a)  They form lysosomes.                 exist in the cytoplasm of eukaryotic cells.
            (b)  They concentrate and pack
                secretions, such as enzymes.          It anchors proteins  or organelles,  such
            (c)  They are involved in transformation   as nucleus  to their  fixed  location.  The
                of spermatids into mature             cytoskeleton  consists  of microtubules,
                spermatozoa.                          microfilaments and intermediate filaments
            (d)  They are involved in formation of    (Figure 1.17).
                primary cell walls in plants.








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