Endocytosis vs Exocytosis
A cell is enveloped with cell membrane as a barrier to external things. So, having such membrane, cells need some kind of transportation mechanism to connect with the external environment. As an example; cells need to obtain nutrients and excrete waste from the cell. For that purpose, cells have four basic mechanisms of transportation. Diffusion, osmosis, active transport, and bulk transport are them. Diffusion and osmosis are passive processes, whereas active transport and bulk transport are active processes that consume energy. Endocytosis and exocytosis are bulk transportation mechanisms, which transport big particles through the plasma membrane either from cell to the external environment or from the external environment to the cell. Both these mechanisms form membrane bound vesicles in the mean of transportation.
What is Endocytosis?
Endocytosis is transport of macromolecules, large particles, and polar substances that cannot enter through the non-polar membrane into cells. The extension of plasma membrane or in folding the membrane in to the cell vesicle is formed, in the process of endocytosis. After it has entered to the cytoplasm this vesicle binds with another membrane-bound organelle such as vacuole or Endoplasmic Reticulum (ER).
There are four types of endocytosis. Clathrin–mediated endocytosis, caveolae, macropinocytosis, and phagocytosis are them (Mark, 2001). Endocytosis results in immune response, in signal transduction, neural function and in pathological conditions (Mark, 2001). This is harder in plant cell than animal cell, since the plant cell is surrounded by a cell wall. With the turgor pressure, plasma membrane of a plant cell is pressed against the plant cell wall, restricting in folding into the cytoplasm.
What is Exocytosis?
This is opposite of endocytosis process. Waste materials, which are needed to be removed from the cell such as solid, undigested remains, or useful materials that are needed to produce the cell wall are transported outside of the cell through the Exocytosis (Taylor et al, 1998). In the cytoplasm, these materials are packed in to vesicle and directed to the plasma membrane. When the vesicle comes in contact with the plasma membrane, it fuses with the plasma membrane and release those wastes into the external environment. Vesicle becomes part of the plasma membrane (Bolsover et al, 2004).
Exocytosis is important in making the cell wall after the nuclear division of the cell. Polysaccharides and proteins are transported to the cell wall by exocytosis. In plants, nectar is released to attract pollinators by this mechanism. Oil emitted by mustard plants to irritate the herbivores, enzymes released in carnivorous plants, and release of root exudates due to environmental stress occur through the exocytosis.
What is the difference between Endocytosis and Exocytosis?
• Endocytosis is transport of macromolecules, large particles, and polar substances that cannot enter through the non-polar membrane into a cell, whereas exocytosis is transport of molecules or particles outside of the cell.
• Endocytosis involves with the up taking nutrients into the cell, but exocytosis involves in removing waste from the cell.
• Exocytosis involve in the making of the cell wall, but not endocytosis.
• In endocytosis, at the end of the process vesicle bounds with the cellular membrane bound organelles, while in exocytosis vesicle is bound with cellular membrane at the end of the process.
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