Question

Orientation of transmembrane proteins as they are delivered to the plasma membrane.

A. The Golgi apparatus determines their orientation.
B. Chaperone proteins facilitate their correct orientation.
C. The ER signal sequence dictates their orientation.
D. The cytoplasmic environment governs their orientation.

Answer 1

The Golgi apparatus and the cytoplasmic environment determine the orientation of transmembrane proteins as they are delivered to the plasma membrane.

Step-by-step explanation:

The orientation of transmembrane proteins as they are delivered to the plasma membrane is determined by the Golgi apparatus and the cytoplasmic environment.

The Golgi apparatus acts as a sorting and packaging center for proteins. It receives transport vesicles from the endoplasmic reticulum (ER) and modifies the proteins before sending them to their final destinations. The Golgi apparatus recognizes complementary integral membrane proteins embedded in the vesicles and facilitates their correct orientation.

The cytoplasmic environment also plays a role in governing the orientation of transmembrane proteins. Proteins made in the cytoplasm go through post-translational modification and sorting mechanisms before reaching the plasma membrane. Chaperone proteins assist in the proper folding and orientation of these proteins.