Final answer:
Integral membrane proteins are synthesized on ribosomes attached to the ER where they are inserted into the membrane and undergo initial modifications. The modified form of cotranslational import for these proteins specifically involves the ER.
Step-by-step explanation:
The synthesis of integral membrane proteins involves the endoplasmic reticulum (ER). An N-terminal signal sequence guides ribosomes translating integral membrane proteins to the rough endoplasmic reticulum (RER). Here the protein is inserted into the membrane, and stop-transfer sequences prevent it from passing completely through the membrane, resulting in the protein being anchored in the lipid bilayer. After synthesis and initial modifications in the RER, the proteins are moved to the Golgi apparatus where further modifications, such as glycosylation, may occur. Finally, the proteins are sorted in the Golgi and packaged into vesicles which then fuse with the plasma membrane or the membranes of other organelles, incorporating the integral membrane protein into the membrane.
Therefore, integral membrane proteins go through a modified form of cotranslational import that involves the ER, as this is where they are initially synthesized and inserted into the membrane.