Cellular Organelles - NUCLEUS AND DNA

nucleus features

• largest organelle

• stores genetic information

• contains chromatin and nucleolus

• double membraned

• nuclear pores - connect with nucleoplasm

which type of cells dont have a nucleus

enterocytes - red blood cell

why they dont live very long

nucleoplasm

• cytoplasm of the nucleus

• contains nuclear structures like chromosomes and nuclear matrix

• gel-like substance

• surrounded by nuclear membrane

  • Nuclear Lamina

    • Nuclear matrix

Nuclear matrix

• found in the nucleoplasm

• dense network of fibres

  • provides support (like cytoskeleton)

nuclear lamina

• dense fibrillar network - intermediate filaments

• also found in nucleoplasm

• provides mechanical support

• keeps spherical shape of nucleus

• regulates DNA replication and cell division

nucleolus

• largest dark staining part of nucleus

• synthesis of rRNA

nuclear envelope

• membrane around the nucleus

• made up of 2 phospholipid bilayers

  • inner nuclear membrane

  • outer nuclear membrane

Perinuclear space

• space between inner and outer nuclear membrane

• function of which is still being studied

nuclear pores

• channel found in the nuclear envelope where two membranes fuse tg

• allows for transport of molecules

• cytoplasmic and nuclear face

• communication between nucleus and cytoplasm

what molecules does the nuclear pore transport

• proteins; for nuclear lamina or catalyze nuclear activities

• RNA and RNA-protein complexes formed in the nucleus and exported to cytoplasm

chromatin

• double-stranded helical DNA molecule

• wound around globular proteins (histones) - form nucleosomes

• many nucleosomes are packed tightly to form chromatin

• located in nucleoplasm

forms of chromatin

heterochromatin and euchromatin

heterochromatin

• darkly staining and irregularily scattered

• genetically inactive

• DNA protection, gene regulation, chromosome stability

• it stays inactive to keep certain genes turned off

euchromatin

• dispersed and not readily stainable

• loosely coiled → accessed often

• genetically active

  • carry genes for protein synthesis

chromosomes

• formed during cell division

• tightly coiled chromatin

• Store and organize genetic information