Cell nuclei

Cell Nuclei

The cell nucleus is a membrane-bound organelle found in eukaryotic cells. It contains most of the cell's genetic material, organized as multiple long linear DNA molecules in complex with a large variety of proteins, such as histones, to form chromosomes. The function of the nucleus is to maintain the integrity of these genes and to control the activities of the cell by regulating gene expression.

Structure

The nucleus is surrounded by a double membrane called the nuclear envelope, which separates the contents of the nucleus from the cytoplasm. The nuclear envelope is perforated with nuclear pores that allow the transport of molecules across the nuclear envelope. The interior of the nucleus is filled with a gel-like substance called the nucleoplasm, which contains the chromatin and the nucleolus.

Nuclear Envelope

The nuclear envelope consists of two lipid bilayer membranes: an inner and an outer membrane. The outer membrane is continuous with the endoplasmic reticulum. The space between the two membranes is called the perinuclear space.

Nuclear Pores

Nuclear pores are large protein complexes that cross the nuclear envelope. They allow the transport of molecules such as RNA and ribosomal proteins from the nucleus to the cytoplasm, and the import of proteins, carbohydrates, and lipids into the nucleus.

Chromatin

Chromatin is the complex of DNA and protein found in the nucleus. It is divided into heterochromatin, which is densely packed and transcriptionally inactive, and euchromatin, which is less dense and transcriptionally active.

Nucleolus

The nucleolus is a non-membrane bound structure composed of proteins and nucleic acids found within the nucleus. It is the site of ribosomal RNA (rRNA) synthesis and ribosome assembly.

Function

The primary functions of the nucleus are to:

• Store the cell's hereditary material, or DNA, and coordinate the cell's activities, which include growth, intermediary metabolism, protein synthesis, and reproduction (cell division).
• Regulate gene expression by controlling the transcription of DNA into RNA.
• Facilitate DNA replication during the cell cycle.

Importance in Medicine

Understanding the structure and function of the cell nucleus is crucial in the field of medicine, particularly in the study of genetic disorders, cancer, and cellular aging. Abnormalities in nuclear structure and function can lead to diseases such as progeria, Hutchinson-Gilford syndrome, and various forms of cancer.

Also see

• Eukaryotic cell
• DNA replication
• Gene expression
• Chromosome
• Nucleolus

Cell biology