NUCLEUS

NUCLEUS

DISCOVERY
Nucleus was for the first time described by the English Robert Brown in 1831.
OCCUERENCE AND DISTRIBUTION
Nucleus is present in all eukaryotic cells. The nucleus is centrally located and roughly spherical cellular component which controls all the vital activities of the cytoplasm and carries the heredity material the DNA in it.
CELL WITH NO NUCLEUS:
Prokaryotic have no nucleus. Mammalian erythrocytes (red blood cells) lose their nuclei when they mature.
SIZE
It is typically 10 um in diameter.
IMPORTANCE
It is one of the most important organelle because it controls all the metabolic activities and his the genetic information in the form of chromosomes and DNA.

STRUCTURE OF NUCLEUS
Nucleus consist of
1) Nuclear envelop
2) Nucleolus
3) Nucleoplasm and
4) Chromosomes
NUCLEAR ENVELOP:
The nucleus is bounded by two membranes, which together called nuclear envelope.
The outer membrane of the nuclear envelope is continuous with the endoplasmic reticulum.
NUCLEAR PORES:
Over the surface of the nuclear envelope, are shallow depressions called nuclear pores. These pores helps in the transport of the proteins into the nucleus and mRNA from nucleus into the cytoplasm.
NUMBER OF NUCLEAR PORES:
Egg cells have maximum number of pores, while minimum in RBCs.
NUCLEOLUS:
It is a granular body with in the nucleus and is not bounded by a membrane. There may be one or more nucleoli in the nucleus.
REGIONS OF NUCLEOLUS:
It is composed of two regions; the peripheral granular area composed of precursor which helps in synthesis of ribosomal sub units, and the central febrile area consisting large RNA and DNA.
NUCLEOPLASM:
The space between the nuclear envelope and the nucleolus is filled by a transparent, semi- solid granular ground substance or the matrix known as the nucleoplasm
It is a colloidal mixture of organic and inorganic salts and ions.
FUNCTION OF NUCLEOPLASM:
Nucleoplasm houses nuclear content. It also serves as storage place for enzymes, raw material needed for DNA replication and synthesis of RNA.
ROLE OF NUCLEUS:
RNA SYNTHESIS:
RNA is synthesized and stored in the nucleolus.
FORMATION OF RIBOSOMES:
Proteins imported from the cytoplasm are assembled with RNA forming ribosomal sub units. These sib units then exit the nucleus through the nuclear pores to the cytoplasm, where a large and a small sub units can assembled into a ribosome.