Question

Which of the following will not be co-translationally translocated into the ER?
A. A channel protein on the plasma membrane.

B. A secreted protein.

C. A mitochondrial protein.

D. A Golgi protein.

E. A lysosomal protein.

Answer 1

Option C, mitochondrial protein .

Protein follow two main pathway during sorting process

1) RER pathway also known as secretory pathway

Here protein during translation enter in to ER known as co translation translation. Means as translation occur side by side proteins are inserted in to ER lumen .

. Follow the path ER- golgi- vesicles-- either to lysosome or can be secterd out side or can be a part of membrane.

2) cytosolic pathway

Here protein are synthesized on free ribosome. So after synthesis of protein based on target sequence , translocsted to destination. Most of the protein transporters to cellular organelles follow this pathway.

Eg nucleus, mitochondria, peroxisomes

So in the question only mitochondria protein show cytosolic patway not show co translational ER translation