Final answer:
Collagen synthesis begins on the ribosome and is modified in the endoplasmic reticulum. It is then packaged and modified in the Golgi apparatus before being released extracellularly, where it finally polymerizes into fibers.
Step-by-step explanation:
The polymerization of collagen into large collagen fibers occurs extracellularly. Collagen synthesis begins on the ribosome, where the protein is formed. This nascent protein is then modified in the endoplasmic reticulum (ER); more specifically, it is modified in the rough ER due to the presence of ribosomes. From there, the collagen is packaged into vesicles and further modified as it travels through the Golgi apparatus. Once the collagen precursors are fully processed and ready to form actual fibers, they are transported in secretory vesicles to the plasma membrane, where they are released into the extracellular space. In this space, the collagen molecules undergo polymerization to form the large fibers that provide structural support in tissues.