The cell nucleus is the command center of eukaryotic cells, housing genetic material and regulating gene expression. It features a double-layered nuclear envelope with pores for molecule exchange, a supportive nuclear lamina, and chromatin organization for DNA packaging. The nucleolus and other nuclear bodies perform specialized functions, while nuclear transport relies on pores and karyopherins for selective molecule passage.
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The inner membrane maintains the nucleus's shape and integrity, while the outer membrane participates in protein synthesis
The perinuclear space is continuous with the endoplasmic reticulum's lumen
Nuclear pores are intricate structures that span the envelope, selectively controlling the transport of molecules
The nuclear lamina is a fibrous network beneath the inner nuclear membrane, providing structural support and anchoring chromosomal locations and nuclear pores
Euchromatin and Heterochromatin
Chromatin is present in two states: euchromatin, which is loosely packed and transcriptionally active, and heterochromatin, which is tightly packed and less active
Nuclear Territories
The arrangement of chromosomes within the nucleus is highly organized, with each chromosome occupying a specific territory that can influence gene expression
Components
The nucleolus consists of three main components: fibrillar centers, dense fibrillar components, and granular components, each with specialized roles in rRNA production and processing
Function
The nucleolus is dedicated to the synthesis of ribosomal RNA (rRNA) and the assembly of ribosomes
Types
The nucleus contains various other nuclear bodies, such as Cajal bodies, PML bodies, and speckles, which are involved in functions like RNA splicing, gene regulation, and the cellular response to stress
Selective Gateways
Nuclear transport is orchestrated by nuclear pores that serve as selective gateways, permitting the passive diffusion of small molecules and ions, while larger molecules such as proteins and RNA are transported through a regulated process
Carrier Proteins
Transport is mediated by carrier proteins known as karyopherins, which include importins and exportins
The selective transport system of nuclear pores is essential for preserving the distinct internal environment of the nucleus and for critical processes like gene expression and chromosome maintenance, which depend on the import of regulatory proteins and the export of RNA transcripts
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Nuclear envelope composition
Consists of two lipid bilayers, encases nucleus, protects genetic material.
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Nucleus's role in gene expression regulation
Central to genetic integrity, regulates cellular functions through gene expression.
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Function of nuclear pores
Facilitate selective exchange of molecules between nucleoplasm and cytoplasm.
