Golgi apparatus plant cell

SG, secretion granule V, vacuole Nu, nucleolus G, Golgi apparatus CW, cell wall (of a plant)... 

Moore, P.J., Swords (1991) Spatial organization of the assembly pathways of glycoproteins and complex polysaccharides in the golgi apparatus of plants. J.Cell Biol. 112 589-602. 

Key Words Plant cell-wall Pectin biosynthesis Methylester Golgi apparatus. 

Most organelle membranes, such as the tonoplast (6) and the Golgi apparatus (7), can be separated by density gradient ultracentrifugation of plant cell homogenates. However, other effective methods for the isolation of the plasma membrane (8,9) have been described. Moreover, another method that uses an aqueous two-phase system for the isolation of ER is also described (10). Those interested in these details for these methods should consult the original articles. 

In spite of the variety of appearances of eukaryotic cells, their intracellular structures are essentially the same. Because of their extensive internal membrane structure, however, the problem of precise protein sorting for eukaryotic cells becomes much more difficult than that for bacteria. Figure 4 schematically illustrates this situation. There are various membrane-bound compartments within the cell. Such compartments are called organelles. Besides the plasma membrane, a typical animal cell has the nucleus, the mitochondrion (which has two membranes see Fig. 6), the peroxisome, the ER, the Golgi apparatus, the lysosome, and the endosome, among others. As for the Golgi apparatus, there are more precise distinctions between the cis, medial, and trans cisternae, and the TGN trans Golgi network) (see Fig. 8). In typical plant cells, the chloroplast (which has three membranes see Fig. 7) and the cell wall are added, and the lysosome is replaced with the vacuole. 

The most important membranes in animal cells are the plasma membrane, the inner and outer nuclear membranes, the membranes of the endoplasmic reticulum (ER) and the Golgi apparatus, and the inner and outer mitochondrial membranes. Lysosomes, peroxisomes, and various vesicles are also separated from the cytoplasm by membranes. In plants, additional membranes are seen in the plastids and vacuoles. All membranes show polarity—e., there is a difference in the composition of the inner layer (facing toward the cytoplasm) and the outer layer (facing away from it). 

Pagny, S., Cabanes-Macheteau, M., Gilikin, J.W., Leborgne-Castel, N., Lerouge, R, Boston, R.S., Faye, L., and Gomord, V. (2000). Protein recycling from the Golgi apparatus to the endoplasmic reticulum in plants and its minor contribution to calreticulin retention. Plant Cell 12 739-755. 

Brown, R. M., Herth, W., Franke, W. W., Romanovicz, D. The role of the Golgi apparatus in the biosynthesis and secretion of a cellulosic glycoprotein in Pleurochrysis a model system for the synthesis of structural polysaccharides. In Biogenesis of plant cell wall polysaccharides, pp. 207. Loewus, F. (ed.). New York Academic Press 1973... 

These secretion granules move to the surface and are released from the cell. In this process of exocytosis the membranes surrounding the granules fuse with the outer cell membrane. The rough ER appears to contribute membrane material to the smooth ER and Golgi apparatus, while material from Golgi membranes can become incorporated into the outer cell membrane and into lysosomes. Outer mitochondrial membranes and membranes around vacuoles in plant cells may also be derived directly from the ER. Outer membrane materials are probably "recycled" by endocytosis. 

In the past few years, some impressive observations have been made by microscopists studying cells actively engaged in cellulose synthesis. It is now generally accepted by most workers that, in the bacterium A. xylinum, in most algae, and in all of the higher plants, cellulose is synthesized at the cell surface by an enzyme system localized in the plasma membrane. The notable exception to this conclusion concerns those algae which synthesize a cell wall composed of cellulosic scales such scales are synthesized intracellularly by way of the Golgi apparatus (see Ref. 57 and references cited therein). 

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