[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 apparatus, the 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.