3 For each alternative ending to the following sentence indi

3. For each alternative ending to the following sentence, indicate why the ending is false: 4 pts

“Proteins destined to enter the rough endoplasmic reticulum _______”

a. are transported into the ER after their synthesis is complete.

b. are synthesized on free ribosomes in the cytosol.

c. cross the membrane in a folded state.

d. must be proteins that will be secreted from the cell.

Solution

Answer:

Proteins destined to enter the rough endoplasmic reticulum are transported into the ER after their synthesis is complete. This statement is false because, replication (synthesis or amplification of DNA) and transcription (synthesis of m-RNA) takes place in the nucleus whereas; translation (synthesis of proteins) takes place in the cytoplasm. The m-RNA which is synthesized is transported to cytoplasm with the help of ribosomes present on the surface of endoplasmic reticulum. Hence, the proteins do not enter the rough endoplasmic reticulum after the synthesis is completed.

Proteins destined to enter the rough endoplasmic reticulum are synthesized ion free ribosomes in the cytosol. This statement is False because, the proteins are synthesized in the cytosol with the help of ribosomes but they are not synthesized on free ribosomes in the cytosol.

Proteins destined to enter the rough endoplasmic reticulum cross the membrane in a folded state. This statement is also false because, they are not crossed the membrane in a folded state. They are transported in the nascent form with the form of unfolded state.

Proteins destined to enter the rough endoplasmic reticulum must be proteins that will be secreted from the cell. This statement is also false because, proteins are release from the cell after their final process done in Trans-Golgi, but whatever releases from there is not a protein.