Nucleus- Definition , Structure, Characteristics and Functions – Class 9

Nucleus – Definition

Nucleus is the largest cell organelle which contains genes and it controls the activities of the cell. It is also called the brain of a cell.

Structure of Nucleus 

• Nucleus  is composed of a double layered covering called a head nuclear membrane. It has numerous pores called nuclear pores. They transfer the materials from inside the nucleus to cytoplasm
• The nucleus contains chromosomes. When they are visible as rod-shaped structures only when the cell is about to divide. 
• Nucleus encloses a liquid ground substance called nucleoplasm. It contains nucleolus and chromatin material.

Also Check – Cell membrane (Plasma Membrane )- Structure, Composition, Characteristics and 6 Important Functions

5 Important Characteristics of Nucleus

1. Nucleus is Membrane enclosed cell organelle found in Eukaryotic cell
2. Nucleus is the largest cell organelle which is mostly spherical and dense. 
3. Nuclear membrane has pores to allow substances to enter and leave.
4. Nucleus contains a network of thread-like structures called chromatin fibers which contain DNA.
5. Nucleus also contains RNA that directs protein synthesis.

Functions of Nucleus

1. Nucleus regulates cell functions.
2. If Nucleus is removed, the cell dies.
3. Nucleus contains chromosomes (bearers of genes that control hereditary characters). Read more…

Also check – 5 Important Functions of Nucleus