The nuclear envelope differs from the plasma membrane in that it
- A. is made of protein only
- B. has no pores of any kind
- C. consists of two membranes perforated by pores
- D. is freely permeable to all molecules
Explanation
Two membranes enclose the nucleus, and the pores that pierce them at intervals let mRNA and ribosomal subunits out and let nucleotides, enzymes and regulatory proteins in, while keeping the chromosomes separate from the cytoplasm. The outer membrane is continuous with the rough endoplasmic reticulum. Free permeability would defeat the whole purpose of enclosing the genetic material.
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