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Multiple Choice
A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized __________.
A
in the ribosomes of the mitochondria
B
on free cytoplasmic ribosomes
C
in the smooth endoplasmic reticulum
D
in the plasma membrane
E
in the rough endoplasmic reticulum
Verified step by step guidance
1
Understand the role of the rough endoplasmic reticulum (RER) in protein synthesis. The RER is studded with ribosomes, which are the sites of protein synthesis, particularly for proteins that are to be secreted, incorporated into the plasma membrane, or sent to an organelle.
Recognize that proteins destined for the plasma membrane are typically synthesized in the RER. This is because the RER is involved in the initial stages of protein processing and modification, which are crucial for membrane proteins.
Consider the pathway of a protein synthesized in the RER. After synthesis, these proteins are transported to the Golgi apparatus for further modification and sorting.
After processing in the Golgi apparatus, the proteins are packaged into vesicles that transport them to the plasma membrane.
Conclude that the synthesis of a protein that functions in the plasma membrane is most likely initiated in the rough endoplasmic reticulum, as this organelle is specialized for the synthesis of membrane-bound and secretory proteins.