PLEASE HELP -- Imagine protein X, destined to span the plasma membrane. Assume that the mRNA carrying the genetic message for protein X has already been translated by ribosomes in a cell culture. If you fractionate the cells, in which fraction would you find protein X? Explain by describing its transit through the cell.

Protein X would be ultimately present in the subcellular fraction containing membrane fragments

Explanation:

It is possible to trace the synthesis and transport of a membrane protein by the following steps:

1- The amino acids of the membrane protein are joined together in the ribosome to form a polypeptide chain (in this case, the protein X).

2- A signal sequence of the growing polypeptide produces the binding of the ribosome to the membrane of the endoplasmic reticulum (ER) and the insertion of this polypeptide chain into the ER.

3-The protein is released into a vesicle from the ER to be exported to the Golgi complex.

4- The membrane protein is transported by the Golgi complex to the cell membrane by the formation of a secretory vesicle that fuses with the plasma membrane, thus being finally embedded in the lipid bilayer.

ysosomes are membrane-bound vesicles that contain digestive enzymes, such as glycosidases, proteases and sulfatases. lysosomal enzymes are synthesized in the endoplasmic reticulum (er), are transported to the golgi apparatus, and are tagged for lysosomes by the addition of mannose-6-phosphate label.

explanation:

the answer is d (apex) good luck : ))