Structure and Function of the Nucleus in Eukaryotic Cells

Overview

• The nucleus is one of the most important organelles in a eukaryotic cell.
• Primary function: Contains the genetic material (DNA) of the cell.

Structure of the Nucleus

Membranes

• The nucleus is surrounded by two separate membranes:
  • Outer membrane
  • Inner membrane
• These membranes separate the nucleus from the cytoplasm.
• Nucleoplasm: Fluid inside the nucleus, not continuous with the cytoplasm.

Transport Between Nucleus and Cytoplasm

• Nuclear pore complexes: Allow for selective transport between the nucleoplasm and the cytoplasm.
  • Transport substances like mRNA (out to cytoplasm) and proteins (into the nucleus).
  • Highly selective, recognizes specific signals on proteins.

Nucleolus

• The dense, compact region within the nucleus.
• Primary function: Site of ribosome assembly.
  • Produces ribosomal RNA (rRNA).
  • rRNA is assembled with proteins to form ribosomes, which are then transported to the cytoplasm.

Association with Endoplasmic Reticulum (ER)

• The outer nuclear membrane is continuous with the membranes of the endoplasmic reticulum.
  • Endoplasmic Reticulum (ER): An important site for protein and lipid synthesis.
  • The space inside the ER is continuous with the space between the inner and outer nuclear membranes.

Nuclear Envelope

• Composed of:
  • Inner membrane
  • Outer membrane
  • Nuclear pores
• Encloses the nucleus, maintaining its structure and function.