AAMC MCAT Guide Bio Passage 1 #2

[TheRealAngeleno]

Hey guys in Passage 1 question #2, I thought that all proteins within the cell are synthesized on ribosomes within the cytosol while proteins bound for the plasma membrane as well as those that are excreted into the environment are synthesized on the rough endoplasmic reticulum. Obviously this is wrong and so I just wanted some clarification. So pretty much proteins within organelles, the membranes of these organelles, the plasma membrane and those destined to be secreted into the environment are synthesized within the rough endoplasmic reticulum? Thanks a lot.

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[PiBond]

Hey guys in Passage 1 question #2, I thought that all proteins within the cell are synthesized on ribosomes within the cytosol while proteins bound for the plasma membrane as well as those that are excreted into the environment are synthesized on the rough endoplasmic reticulum. Obviously this is wrong and so I just wanted some clarification. So pretty much proteins within organelles, the membranes of these organelles, the plasma membrane and those destined to be secreted into the environment are synthesized within the rough endoplasmic reticulum? Thanks a lot.

If the protein is a cytosolic protein (ie glycolytic protein) it begins and ends translation in the cytosol. If the protein is a membrane bound, secreted, ER resident protein, or if it's bound for an organelle like the lysosome it will begin translation in the cytosol but it's signal sequence will cause it to be directed to the rough ER where it will finish translation, then move to the golgi, and then dispatched to its final location from the trans Golgi network. In this case to the lysosome since GBA is a lysosomal protein

 

[TheRealAngeleno]

If the protein is a cytosolic protein (ie glycolytic protein) it begins and ends translation in the cytosol. If the protein is a membrane bound, secreted, ER resident protein, or if it's bound for an organelle like the lysosome it will begin translation in the cytosol but it's signal sequence will cause it to be directed to the rough ER where it will finish translation, then move to the golgi, and then dispatched to its final location from the trans Golgi network. In this case to the lysosome since GBA is a lysosomal protein

Ah nice. Thank you for the clarification!