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[Biology Form 4] How to Synthesis Extracellular Protein?


  • Extracellular protein is the protein that is destined for export from a cell such as digestive enzyme that is made by pancreas cell.

  • The organelles that involved in the process are nucleus, ribosome, RER,Golgi apparatus and mitochondria.

  • Flow chart shows how the internal membrane system of a cell packages a protein for export.


  • 1. Instructions for making protein are transcribed from DNA by RNA in the nucleus.
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    2. RNA leaves the nucleus through nuclear pore and proceeds to a ribosome located on the RER.
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    3. Ribosome synthesis the correct sequence of amino acids for synthesizing that particular protein as instructed.
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    4. When protein synthesis is complete, the protein travels through the RER and is then encapsulated in a transport vesicle.
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    5. The transport vesicle fuses with a Golgi apparatus, releasing the protein.
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    6. In the Golgi apparatusthe protein is further modified and is then shunted to the ends of Golgi apparatus or cisternae. There, the protein waits for a secretory vesicle.
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    7. The secretory vesicle will carry the protein to the plasma membrane of the cell and fuses with it. Then, the protein is released outside the cell.