What does the nuclear envelope consist of?

The nuclear envelope consists of two membranes, which are the inner and outer nuclear membranes. This double membrane structure surrounds the nucleus of eukaryotic cells and serves several critical functions. The outer membrane is continuous with the endoplasmic reticulum, allowing for communication and material exchange between the nucleus and the cytoplasm. The space between the two membranes is known as the perinuclear space.

Additionally, the nuclear envelope plays a crucial role in protecting the genetic material stored within the nucleus while regulating what enters and exits, such as RNA and proteins. It is vital for maintaining the integrity of the nucleus and thus supports essential cellular activities such as gene expression and DNA replication. The presence of two membranes, and their associated nuclear pore complexes, is essential for these functions, making the selection of the option referring to two membranes accurate.