Question

The fact that the outer membrane of the nuclear envelope has bound ribosomes allows one to most reliably conclude that

A) at least some of the proteins that function in the nuclear envelope are made by the ribosomes on the nuclear envelope.
B) the nuclear envelope is not part of the endomembrane system.
C) the nuclear envelope is physically separated from the endoplasmic reticulum.
D) small vesicles from the Golgi fuse with the nuclear envelope.
E) nuclear pore complexes contain proteins.

Answer 1

The bound ribosomes on the nuclear envelope's outer membrane suggest that proteins for the nuclear envelope are synthesized there, confirming that it is part of the endomembrane system.

Step-by-step explanation:

The presence of bound ribosomes on the outer membrane of the nuclear envelope is a key indicator that the nuclear envelope is indeed part of the endomembrane system. Since the nuclear envelope's outer membrane is contiguous with the rough endoplasmic reticulum (RER), we can deduce that some of the proteins that function within the nuclear envelope are synthesized by these ribosomes. This is confirmed by understanding the role of the endomembrane system, which includes the nuclear envelope, ER, Golgi apparatus, lysosomes, vesicles, as well as the plasma membrane. These components work together to modify, package, tag, and transport proteins and lipids that form the membranes.

Therefore, the correct answer to the question is A) at least some of the proteins that function in the nuclear envelope are made by the ribosomes on the nuclear envelope. This is because the nuclear envelope's inner and outer membranes are distinct yet connected, and the outer membrane is continuous with the RER, where ribosomes are bound and engage in protein synthesis.