Final answer:
In a pulse-chase experiment, a longer chase period allows radiolabeled proteins to move farther along in their intracellular journey, often ending up in the plasma membrane or secreted outside the cell.
Step-by-step explanation:
In a pulse-chase procedure, radiolabeled proteins will initially be found in the site of their synthesis, such as ribosomes or the endoplasmic reticulum. As the chase period extends, these proteins are processed, modified, and then trafficked to their target destinations inside the cell, such as the Golgi apparatus, lysosomes, the plasma membrane, or they may even be secreted outside the cell. A longer chase period allows further movement and hence, after a more extended chase, radiolabeled proteins could likely be found in cellular locations farther downstream in the secretory pathway such as in the plasma membrane or in the extracellular space, depending on the nature of the proteins and their final destinations within the cell.
For example, autoradiography can show that over time, the radioactive label appears first in organelles like the endoplasmic reticulum and then in the Golgi apparatus, moving through this secretory pathway. If the chase is prolonged, the label will be found in structures that are involved in storing, recycling, or secreting proteins, depending on the protein's function.