Question

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)

Answer 1

Answer/Explanation:

First, the polypeptides are synthesised and folded in the endoplasmic reticulum, which is a series of folded membranes.

Then, the polypeptide is packaged into vesicles and moved into the Golgi apparatus, which are stacks of flattened sacs. At the Golgi apparatus, the polypeptide is modified, forming the final structure of the protein. The proteins are then packaged in to vesicles to be transported to their final destination outside of the cell.

The proteins are delivered outside the cell in vesicles via a process called exocytosis. The vesicles reach the membrane, fuse with the membrane, and are then delivered outside the cell.