Question

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.)
Options:
a. Cytoplasm only, ER --> cytoplasm,
b. ER --> Golgi --> outside cell,
c. cytoplasm --> ER --> outside cell,
d. Golgi --> ER --> outside cell,
e. cytoplasm --> Golgi --> outside cell,
f. nucleus --> cytoplasm,
g. ER --> Golgi --> cytoplasm

Answer 1

PFK: cytoplasm

insulin: ER--> Golgi--> outside cell

Step-by-step explanation:

As described in the question, the enzyme phosphofructokinase (PFK) functions is a cells cytoplasm. Enzymes are proteins and proteins are made in the ribosomes of a cell. As ribosomes are present in the cytoplasm, hence PFK once made in the ribosomes will be released into the cytoplasm.

As for insulin, it will be made in the ribosomes. from there, it will move to the Endoplasmic Reticulum for packaging. Then to the Golgi complex for modifications and further packaging. Only after these stages, it will be ready to move out from where it is produces to areas where it has to be used.