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CELL NUCLEUS

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INTRODUCTION

HISTORICAL PERSPECTIVE

STRUCTURE

MORPHOLOGY

FUNCTION

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“Nucleus” is a Latin word meaning Kernel

It is the “CONTROL CENTER” of the cell

It was First cell organelle to be discovered

It is membrane bound organelle found in eukaryotic cells

Main functions are

- to maintain the integrity of genes

- to control the activities of the cell by regulating gene expression

INTRODUCTION

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NUCLEUS

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Also known as perinuclear envelope, nuclear membrane or

karyotheca

Encloses the nucleus and separates the cell's genetic material

from the surrounding cytoplasm

It is a lipid bilayer

Consists two cellular membranes, an inner & outer membrane,

arranged parallel to one another and separated by 10-50(nm)

of space

NUCLEAR ENVELOPE

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NUCLEUS

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OUTER MEMBRANE 6 nm thick

Faces cytoplasm and is continuous at certain sites with the

RER

A loosely arranged mesh of intermediate filaments (vimentin)

Ribosomes stud the cytoplasmic surface of the outer nuclear

membrane

Ribosomes synthesize proteins that enter the perinuclear

cisterna (space between two membranes 20-40nm wide)

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Faces the nuclear material

Primary site for location of inner nuclear membrane proteins IMP

Inner membrane proteins – LAP2, SUN1, EMERIN, MAN1, LBR

(used during formation of NE during mitosis as well as some role

in transcriptional activity)

Outer and inner membranes are fused at the nuclear pore

complex sites

Inner Membrane is supported underneath by Nuclear lamina

INNER MEMBRANE

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Nucleolus is the discrete densely

stained structure found in nucleus

It is a nuclear inclusion that is not

surrounded by a membrane

Present in cells that are actively

synthesizing proteins

Its size depends on metabolic

activity of cell

Average size .5-5um in dia

NUCLEOLUS

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It is generally detectable when the

cell is in interphase

Synthesis of RNA and its assembly

into ribosome precursors- main

function

More than one nucleolus can be

present in the nucleus 3nucleoli , nucleus of the

spinosum cell layer of skin

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Anucleated cells- which contain no nuclei, thus has no capacity to divide eg.

RBC Platelets

Polynucleated cells- With multiple nuclei eg. Species of protozoa Some fungi Intestinal parasites like giardia Giant cells in inflammation

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