Which structure is present in the nuclear membrane (envelope) that is not found in the cell membrane?

• A. Nuclear pores
• B. Cholesterol molecules
• C. Phospholipid bilayer
• D. Glycoproteins

Answer: (A)

Verified step by step guidance

1. Understand the structure and function of the nuclear membrane (envelope) and the cell membrane. Both membranes are composed of a phospholipid bilayer, but they have distinct features.
2. Identify the unique components of the nuclear membrane. The nuclear membrane contains nuclear pores, which are large protein complexes that span the nuclear envelope, allowing the transport of molecules between the nucleus and the cytoplasm.
3. Compare the components of the nuclear membrane with those of the cell membrane. The cell membrane also contains a phospholipid bilayer, cholesterol molecules, and glycoproteins, but it does not have nuclear pores.
4. Recognize that nuclear pores are specific to the nuclear membrane and are not found in the cell membrane. This is a key distinguishing feature.
5. Conclude that the structure present in the nuclear membrane but not in the cell membrane is the nuclear pores, which facilitate selective transport between the nucleus and the cytoplasm.