Nucleus: Justify the presence of pores in the nuclear membrane

Nucleus: Justify the presence of pores in the nuclear membrane.

Nuclear pores regulate material exchange between the nucleus and cytoplasm while maintaining nuclear integrity.

• Transport: Controls movement of RNA, proteins, and molecules.

• mRNA Export: Allows mRNA to exit for protein synthesis.

• Waste Removal: Expels non-functional RNA and waste.

Thus, nuclear pores ensure controlled exchange and protection, vital for cell function.

Structure of Nuclear Pores

Nuclear pores are large protein complexes embedded in the nuclear envelope, regulating the exchange of materials between the nucleus and cytoplasm.

Key Structural Features:

🔹 Nuclear Pore Complex (NPC) – A massive, basket-like structure made of ~30 different nucleoporins (Nups).

1. Central Framework (Core Scaffold)

• Forms the main structural ring spanning the nuclear envelope.
• Composed of Y-complex nucleoporins, providing stability.

2. Cytoplasmic Ring & Cytoplasmic Filaments

• Faces the cytoplasm.
• Filaments extend outward, helping in cargo recognition and transport.

3. Nuclear Ring & Nuclear Basket

• Faces the nucleus.
• Basket-like structure assists in the export of RNAs and proteins.

4. Transport Channel (Central Pore)

• FG-Nucleoporins (rich in Phenylalanine-Glycine repeats) line the channel.
• Creates a selective barrier allowing small molecules to diffuse and large molecules (like RNA & proteins) to pass via active transport.

Function:

Regulates RNA, ribosomal subunits, and proteins transport.
Maintains nuclear compartment integrity.
Controls signal-dependent transport via importins/exportins.