A question regarding the Jameison/Paladae experiment over the secretory pathway in a cell.
They exposed pancreatic cells to a pulse of radioactive methionine and then used EM autoradiography to track the movement of secreted proteins through the cell, from the beginning of translation until they reached their destination.
Data curves shows that protein levels do not drop 0% in ER or Golgi, and the curve regarding secretory vesicles will not reach 100%, even if we wait a long time. Why is this?
Select all that are correct.
Not all membrane proteins are secreted after synthesis; some remain as resident proteins of other organelles.
The half-life of the radioactive sulfur is pretty short, some of it has already decayed by 120'.
Some secreted, radioactive proteins have been taken back up by the cell, through endocytosis.
There is reverse traffic of proteins between organelle type B and types A and C.