Question

Part c - protein targeting pathways 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: phosphofructokinase (pfk) is an enzyme that functions in the cytoplasm during glycolysis. 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.)

Answer 1

This question lack some options you can search in the search engine to get full question but I also attached the options in the end of this answer.

Answer:

The sequence of events that occur are as follow:

PFK (protein)

cytoplasm only Insulin protein (targeting pathway)

ER > Golgi > outside cell

Explanation:

In eukaryotic cells there are two major pathways targeting for proteins encoded by nucleus.

Production site of proteins

PFK protein function in cytoplasm are translated particularly on the free ribosomes found in cytoplasm and released on the same site (cytoplasm).

Insulin Protein are the part of major compartments in endomembrane system. It is directly secreted by cell therefore it is translated on endoplasmic reticulum bounded ribosomes. These proteins can be found in two places as end-product of translation.

storage sites of proteins

Firstly, if protein is targeted to endomembrane system’s membrane it can be found in endoplasmic reticulum.

Secondly, if the protein is targeted to inside or outside of the endomembrane system’s organelle it can be found in lumen of rough endoplasmic reticulum.

Traveling pathway of proteins

From rough endoplasmic reticulum either from lumen or membrane these non-cytoplasmic proteins reach (move) to (in) Golgi apparatus for sorting and packaging before being delivered to their final site of action.

Missing 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 --> cytoplasm

Protein Targeting Pathway

PFK _______________

Insulin _______________

Answer 2

For PFK protein, the targeting pathway is CYTOPLASM ONLY.
For insulin protein, the targeting pathway is: ENDOPLASMIC RETICULUM TO THE GOLGI BODY TO THE OUTSIDE OF THE CELL.
There are basically two general targeting pathways for proteins in the eukaryotic cells. Proteins that function in the cytoplasm are released directly into the cytoplasm while other proteins are translated on ribosomes that are bound to rough endoplasmic reticulum.