Final answer:
Ribosomes are the organelles that synthesize proteins and are often referred to as the "protein factory" of the cell. They are located on the rough endoplasmic reticulum or in the cytoplasm. The endoplasmic reticulum, specifically the rough endoplasmic reticulum, is the correct answer for the organelle involved in protein synthesis.
Step-by-step explanation:
The organelle that is involved in the synthesis of proteins and is often referred to as the "protein factory" of the cell is the ribosome. Ribosomes are either located on the surface of the rough endoplasmic reticulum or floating freely in the cytoplasm of both eukaryotic and prokaryotic cells. In eukaryotic cells, the nucleus directs the synthesis of proteins by providing the RNA blueprint, which ribosomes use to assemble amino acids into proteins. The proteins made on the ribosomes attached to the rough endoplasmic reticulum enter the ER lumen, where they may undergo modifications. Then these proteins are packaged into vesicles and sent to the Golgi apparatus for further modification, sorting, and shipment to their final destinations.
To answer the multiple-choice question provided, the correct option from the list is B) Endoplasmic reticulum, specifically the rough endoplasmic reticulum segment that holds ribosomes for protein synthesis.