How do the rough Endoplasmic Reticulum and the Golgi Apparatus act in the production and releasing of proteins?
The Rough Endoplasmic Reticulum(RER) is involved in the production of proteins. ie., on the membrane of RER, large numbers of ribosomes are attached. The ribosomes are the actual sites for protein synthesis. The ribosomes attached to the RER are involved in the synthesis of proteins that are meant to be transported outside the cell (ie., secreted) like several enzymes.
The ribosomes on RER synthesise the proteins and release them into the lumen of RER. After processing and folding, the proteins are packaged into vesicles called "transition vesicles" which are formed by the RER membrane getting pinched around the cargo. These transition vesicles then move towards the Golgi apparatus.
Once they reach the Golgi body, the transition vesicles enter it through the cis side of Golgi body by merging with the Golgi stacks. Within the Golgi body (or apparatus), the proteins undergo further processing, concentrating and also a tagging. The tag determines the target location and the function of the processed protein. Then the protein gets trafficked through the Golgi stacks and finally gets released at the trans side in the form of a secretory vesicle. The secretory vesicle gets released to the outside of the cell only on receiving stimuli.
Thus the RER and Golgi are involved in the production and release of proteins.
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