Nuclear Envelope Continuity with Rough ER

Steps:

• Recall that rough endoplasmic reticulum (RER) is a network of membranes studded with ribosomes for protein synthesis.
• Note that the RER originates from and connects directly to the nuclear envelope in eukaryotic cells.
• Identify the nuclear envelope as a double membrane surrounding the nucleus, with its outer layer resembling RER.
• Confirm this continuity facilitates the transport of newly synthesized proteins from the nucleus to the cytoplasm.

Why D is correct:

• The outer membrane of the nuclear envelope is continuous with the RER membrane, as defined in eukaryotic cell structure, enabling seamless protein processing and transport.

Why the others are wrong:

• A: The cell surface membrane (plasma membrane) is a distinct boundary lipid bilayer, not connected to the RER.
• B: The Golgi body membrane processes proteins via vesicles from the RER but remains separate, without direct continuity.
• C: The mitochondrion has independent double membranes for energy production, unrelated to RER structure.

Final answer: D