The DNA in a cell’s nucleus encodes proteins that are eventually targeted to every membrane and compartment in the cell, as well as proteins that are targeted for secretion from the cell. For example, consider these two proteins:
1. Phosphofructokinase (PFK) is an enzyme that functions in the cytoplasm during glycolysis.
2. Insulin, a protein that regulates blood sugar levels, is secreted from specialized pancreatic cells.
Assume that you can track the cellular locations of these two proteins from the time that translation is complete until the proteins reach their final destinations.
For each protein, identify its targeting pathway: the sequence of cellular locations in which the protein is found from when translation is complete until it reaches its final (functional) destination. (Note that if an organelle is listed in a pathway, the location implied is inside the organelle, not in the membrane that surrounds the organelle.)
Options:Cytoplasm only, ER --> cytoplasm, ER --> Golgi --> outside cell, cytoplasm --> ER --> outside cell, Golgi --> ER --> outside cell, cytoplasm --> Golgi --> outside cell, nucleus --> cytoplasm, ER --> Golgi --> cytoplasmProtein Targeting Pathwaya. PFK _b. Insulin _

There are some proteins which are made inside a cell and have to function inside the same cell whereas there are other proteins which are made inside one cell and have to be transported to another cell where they perform their functions.

The proteins which have to function in the same cell like the PFK are made in the ribosomes and released into the cells cytoplasm to perform their functions.

The proteins which need to be transported like insulin are modified and packaged. These proteins are formed in the ribosomes which are attached to the rough Endoplasmic Reticulum. From there, these proteins are transferred to the Golgi complex where they are modified and packaged. From the Golgi complex, these proteins are transported outside the cells via vesicles.