Final answer:
After a protein reaches its destination, it can either fuse with lysosomes or be exported to the plasma membrane. These final steps in protein trafficking reflect the protein's incorporation into cellular machinery or release external to the cell.
Step-by-step explanation:
Possibilities After Protein Targeting
Once a protein has reached its destination, the targeting signal has several possibilities.
However, when considering the life cycle of proteins within a cell and how they are sorted and directed to their appropriate locations, we can narrow down the possibilities considerably.
After proteins are packaged in the endoplasmic reticulum (ER), they may undergo a sequence of modifications and sorting processes.
The Golgi apparatus plays a significant role in post-translational modification of these proteins.
Based on your question, the two main possibilities for a protein after reaching its destination are as follows:
- Fusion with lysosomes; where the protein is delivered to a lysosome for degradation or use within that organelle.
- Export to the plasma membrane; where the protein is involved in the cell's interaction with its environment, including cell signaling, or it could be secreted from the cell.
The correct answer to the given question is 'C) Fusion with lysosomes; export to the plasma membrane'.
This reflects the final steps of a protein's journey, as previously synthesized proteins can either be incorporated into the cellular mechanism via lysosomes, or be exported out of the cell to fulfill their function.