NUCLEUS:- (Nucleus or kernal means central thing) It is the main organ in a eukaryotic cell that controls functions of all other organelles.
Location :- In animals cells it is present in the center, while in plant cells it is present at a side due to large vacuole.
Occurrence:- a prominent nucleus present in eukaryotic cells.in prokaryotes nucleus is not present. Only nuclear materials DNA or Chromosomes are present.
Shape:- nucleus may be round, oval, crescent or of other shaped.
Structure:- Nucleus is bounded by double membrane called nuclear envelope or nuclear membrane. Nuclear membrane contain small pores called nuclear pores that make it semi permeable. Inside nuclear envelope a fluid called nucleoplasm is present. The nucleoplasm contain one or more nucleoli (singular is nucleolus). It is a dense spot where ribosomal RNA is formed and assembled to Ribosome. Chromosomes are visible in nucleus during interphase of cell division. In prokaryotes chromosome is only condensed form of DNA, while in eukaryotes chromosome is the combination of DNA and histone proteins. Each organism has a fixed number of chromosomes.
Functions :- It controls functions of all other organelles. It means it is control center for all activities of the cell.