Which organelle is described as a network of canals within the cytoplasm where large proteins are made from smaller pieces (anabolism)?

• A. Nucleus
• B. Mitochondria
• C. Endoplasmic Reticulum
• D. Ribosomes

Answer: (C)

Proteins are built by ribosomes and then processed and transported through a continuous membrane system that forms a network of canals in the cytoplasm: the Endoplasmic Reticulum. This organelle provides a vast, interconnected surface where ribosomes on the rough ER synthesize polypeptide chains (the large proteins built from smaller amino-acid chains) and where those nascent proteins are folded, modified, and packaged for delivery to the Golgi or other destinations. The rough ER specifically hosts ribosomes and is key for synthesizing proteins destined for secretion or membranes, while the smooth ER handles lipid synthesis and other functions. The other options don’t describe a membrane network in the cytoplasm, whereas the Endoplasmic Reticulum uniquely fits both the canal-like network and its central role in protein synthesis and processing.