Nucleus” is a Latin word meaning Kernel It is the “CONTROL CENTER” of the cell Average diameter of nucleus is 6um, which occupies around 10% of cell volume Nuclear Envelope Nuclear Pores and complex Nuclear lamina Chromosomes & Chromatin Nucleolus Nucleoplasm

1. Ultra structure of
Nucleus
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2.  “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 .
Intorductions

3. Average diameter of nucleus is 6um, which occupies around 10% of
cell volume
 Nuclear Envelope
 Nuclear Pores and complex
 Nuclear lamina
 Chromosomes & Chromatin
 Nucleolus
 Nucleoplasm
Structure

4.  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.
 The membranes of the nuclear envelope serve as a barrier that keeps ions,
solutes ,and macro- molecules from passing freely between the nucleus
and cytoplasm.
Nuclear envelope

6. 0uterMembrane0uterMembrane
 6 nm thick
 Faces cytoplasm and is continuous at certain sites with the RER
 A loosely arranged mesh of intermediate filaments (vimentin)
 Ribosome stud the cytoplasmic surface of the outer nuclear membrane
 Ribosome synthesize proteins that enter the perinuclear cisterna (space
between two membranes 10-50nm wide)

7.  Faces the nuclear material
 Primary site for location of inner nuclear membrane proteins IMP
 Inner membrane proteins – used during formation of nuclear envelope
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.
InnermembraneInnermembrane

9.  Network of intermediate filaments, The filament of the nuclear lamina are
approximately 10 nm in diameter and composed of polypeptides, called
lamins. Composed primarily of lamins A, B1, B2 and C
 Helps in organizing the nuclear envelope and perinuclear chromatin ,Also
plays a role in DNA elongation phase
 Essential during mitotic events where, Phosphorylation of lamins leads to
disassembly, and dephosphorylation results in reassembly of the nuclear
envelope.
 Apoptosis a highly regulated process in which nuclear lamina is disassembled
following proteolytic activity of caspase protein.
NuclearlaminaNuclearlamina

10.  Nuclear pores are aqueous channels through the nuclear envelope
 Composed of multiple proteins called “nucleoporins.”
 Have molecular weight of 125 KD
 Nucleus of a cell has 3000 - 4000 pores
 Pores are formed by fusion of outer and inner nuclear membranes
 Nuclear Apore complex permits passive movement across the nuclear
envelope via 9-11nm channels by simple diffusion
Nuclear poresand complex

11.  Allows free passage of water soluble molecules
 Most proteins, ribosomal subunits and RNA are transported via transport
factors called KARYOPHERINS
a) Importins –that mediate movement into the nucleus
b) Exportins –that mediate movement out of nucleus
 Nuclear pore complex is composed of nearly 100 proteins, arranged in eight-
fold symmetry around the margin of the pore.

12.  NUCLEARPORE
STRUCTURE
 Cytoplasmic ring
Nucleoplasmic ring
Middlering.
Nucleoplasmic side-
Nuclear basket
 Cytoplasmic side-
displaysfibers

13.  Nucleoplasm is the protoplasm within the nuclear envelope.
 Nucleus is filled with a semi-solid granular slightly acidic ground matrix
called as nucleoplasm.
 The chromatin fibres and nucleolus remain suspended in the nucleoplasm.
 Major component of nucleoplasm are nucleoproteins. Both nucleic acids,
RNA and DNA are present in the nucleoplasm that may occur either as
polymers or monomeric nucleotides.
 Basic proteins like nucleoprotamines, histones and acidic proteins (non-
histone proteins).
NucleoplasmNucleoplasm

14. ► Chromatin are coiled elongated thread like fibres visible during the
interphase and can readily take up basic stains like basic fuschin.
► During cell division where these chromatin fibres get thickened to form a
ribbon like structure called “chromosomes”.
► chromatin is a nucleoprotein complex composed of DNA and proteins and
very small quantity of RNA.
► Chromatin are of 2 types:
Heterochromatin and euchromatin.
Chromatin &chromosomeChromatin &chromosome

15. Heterochromatin: The deeply stained and highly condensed region of the
chromatin that occurs around the nucleolus or at the periphery of the
nucleus.
heterochromatin is transcriptionally inactive and metabolically inert.
Euchromatin is the lightly stained and diffused region of the chromatin that
is transcriptionally active.
 Metaphase chromatin- the chromatin becomes more and more condensed
and compact, making the chromosome visible with a classic four arm
structure, having a pair of sister chromatids attached at centromere.
 Humans have 23 pairs of chromosomes- 22 are autosomes & 2 sex
chromosomes.

16.  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 -5.5µm in diameter.
 It is generally detectable when the cell is in interphase
 Synthesis of rRNA and its assembly into ribosome precursors- main
function
 More than one nucleolus can be present in the nucleus
Nucleolus

18. Conclusively cell nucleusisthestorehouseof everything what aConclusively cell nucleusisthestorehouseof everything what a
cell shall do in future, sinceit handlesthegeneexpression andcell shall do in future, sinceit handlesthegeneexpression and
overall metabolism of celloverall metabolism of cell
thuscalledthuscalled
“DIRECTOR OF CELL”“DIRECTOR OF CELL”

19. THANK YOU