In an experiment investigating the mechanism of protein secretion, researchers tracked the movement of radioactively labeled polypeptides in pancreatic cells. At
various times after the labeling, samples of the cells were observed using an electron
microscope to determine the location of the radioactively labeled polypeptides.
Figure 1 summarizes the results at 5 minutes, 15 minutes, and 30 minutes. The dark
dots in the figure represent the radioactively labeled polypeptides.
Nucleus
Golgi
Secretory
Vesicles
Time
5 min
ER
15 min
30 min
Figure 1. Radioactively labeled polypeptides
Using the experimental results, describe the pathway that secretory proteins take
from their synthesis to their release from the cell. (3 Points)