Eukaryotic Cell: Structure of the Nucleus

Overview of the Nucleus

• Function: Contains the genetic material (DNA) of the cell.
• Structure: Surrounded by two membranes (outer and inner).
• Separation: These membranes isolate the nucleus from the cytoplasm.

Membranes

• Outer and Inner Membranes: Separate nucleus from the cytoplasm.
  • Cytoplasm: Liquid-filled space in the cell.
  • Nucleoplasm: Fluid inside the nucleus.
• Transport: Not continuous between nucleoplasm and cytoplasm.

Nuclear Pore Complex

• Function: Mediates transport between the nucleus and cytoplasm.
• Structure: Spans both outer and inner membranes.
• Selectivity: Only allows transport of proteins with special signals.
• Transport Activities:
  • MRNA: Produced in the nucleus, travels to cytoplasm for translation.
  • Proteins: Enter nucleus for functions like DNA transcription.

Nucleolus

• Location: Center of the nucleus.
• Function: Site of ribosome assembly.
  • Ribosomal RNA: Produced here, not messenger RNA.
• Composition: Densely packed with DNA regions for ribosomal RNA.
• Ribosome Assembly: Combines ribosomal RNA with proteins.
  • Ribosome Trafficking: Assembled ribosomes move out to cytoplasm.
  • Protein Movement: Proteins produced in cytoplasm move into nucleus for assembly.

Endoplasmic Reticulum Association

• Connection: Outer membrane of nucleus is continuous with the membranes of the endoplasmic reticulum.
• Topological Feature: Interior space of ER is linked with space between outer and inner nuclear membranes.

Nuclear Envelope

• Definition: Combination of inner and outer membranes with nuclear pores.
• Role: Encloses the nucleus, maintaining compartmentalization from the rest of the cell.