This is the most poorly drawn cell diagram. I see zero ribosomes, so I figured F was the smooth endoplasmic reticulum. However, now I can see that the curved organelle is the golgi apparatus and F must represent the whole endoplasmic reticulum.
I believe plasma membrane proteins are synthesized in the rough endoplasmic reticulum.
FA2020 p46 Rough endoplasmic reticulum Site of synthesis of secretory (exported) proteins and of N-linked oligosaccharide addition to lysosomal and other proteins.
Free ribosomes—unattached to any membrane; site of synthesis of cytosolic, peroxisomal, and mitochondrial proteins.
Smooth endoplasmic reticulum Site of steroid synthesis and detoxification of drugs and poisons. Lacks surface ribosomes. Location of glucose-6-phosphatase (last step of glycogenolysis).