Deepak yadavm.sc-iii

University of allahabadGuided by:-prf.G K SRIVASTAVA

DISCOVERY

OF

NUCLEUS

Oldest known depiction of cells and

their nuclei by Antonie van

Leeuwenhoek, 1719.

Robert Brown

- introduced the word areola or

nucleus, in the cells of the flower's outer

layer.

Matthias Schleiden

-name "Cytoblast" (cell builder).

Robert Remak and Rudolf Virchow

propagated the new paradigm that cells

are generated solely by cells ("Omnis

cellula e cellula").

The function of the nucleus clear only

later, after mitosis discovered and the

Mendelian rules 20th century).

CELL

NUCLEUS

CELL NUCLEUS

• Latin nucleus or

nuculeus,

meaning kernel.

• The control center of the

cell.

• It contains most of the

cell's genetic material.

PRIMARY FUNCTIONS:

• Repository of genetic information

• Enables synthesis of nearly all proteins

• Houses the nucleolus

• Responsible for production of

ribosomes.

• Selective transportation of regulatory

factors and energy.

COMPOSITION

NUCLEAR ENVELOPE

separates the cell's genetic material from

surrounding cytoplasm.

serve as a barrier between nucleoplasm

and the cytoplasm.

Also known as the nuclear membrane, nucleolemma, or karyotheca.

is the double lipid bilayer membrane which surrounds the genetic material and nucleolus in

eukaryotic cells.

2 lipid bilayer membranes:

•Punctured nuclear pores connect the two membranes.

•Different in protein composition

•Separated by perinuclear space

Inner membrane – associated with nuclear lamina

Outer membrane – continuous with endoplasmic reticulum

Inner Membrane

The inner nuclear membrane encloses the nucleoplasm, and is covered

by the nuclear lamina,

It is connected to the outer membrane by nuclear

pores which penetrate the membranes.

Outer membrane

The outer nuclear membrane is also contiguous with the

endoplasmic reticulum.

While it is physically linked, the outer nuclear membrane

contains various proteins found in far higher concentrations than the endoplasmic

reticulum.

NUCLEOPLASM

made up of water and other

dissolved substances.

act as a suspension for organelles

maintains the shape of the nucleus.

NUCLEAR PORE

composed of multiple proteins

allows the passage of molecules

from inappropriate entering or

exiting the nucleus.

•Large compared to other proteins.

•Octagonal symmetry.

•Mass approx. 125 megaDaltons in vertebrates.

•Cytoplasmic fibrils (tentacle-like)

•Nuclear meshwork

NUCLEAR PORES

The nuclear membrane is punctured by

thousands of nuclear pore complexes

They link the inner and outer nuclear membranes.

Passive diffusion of low molecular weight solutes

Regulated transport of macromolecules larger than 40 kDa

Nuclear import signal: NLS

Nuclear export sequence: NES

Importins: cytoplasm to nucleoplasm

Exportins: nucleoplasm to cytoplasm

GTPase Ran controls interactions of cargo and karyopherin

Function of the nuclear pore

NUCLEAR LAMINA

• structural support for the nuclear

envelope

• anchoring sites for chromosomes

and nuclear pores.

•Intermediate filaments & membrane associated proteins

(Lamins & nuclear lamin-associated membrane proteins)

•Lamin types: A, B1, B2, & C

•Mechanical support

•Regulates cellular events

PROGERIA

• Defective Lamina

protein makes the

nucleus unstable. That

nuclear instability

appears to lead to the

process of premature

aging in Progeria.

CHROMOSOMES

Multiple linear DNA molecules.

During most of the cell cycle

these are organized into chromatin

During cell division the chromatin can

be seen to form the well-defined

chromosomes.

NUCLEOLUS

synthesize rRna and assemble

ribosomes.

HAVE

YOU LEARNED?

Which of the following parts of

nucleus is responsible for the

formation of the ribosomes?

nucleoplasm

nucleolus

nuclear

envelope

chromosomes

A

B nucleolus

C

D

In the nucleus of eukaryotic cells, the genetic material is complexed with protein and organized into linear structures called:

centrioles

plasmidshistones

chromosomesA

B

C chromosomes

D

Provide structural support for the nuclear envelope and anchoring sites for chromosomes and nuclear pores.

Nucleoplasm

Cytosol

Nuclear Lamina

Nuclear MembraneB

CA

D

Nuclear Lamina

The space between the membranes is called:

perinuclearspace

internuclearspace

nuclear space

none of these

A

B

C

D

perinuclearspace

It prevents larger molecules, such as

nucleic acids and larger proteins, from

inappropriately entering or exiting the

nucleus.

nuleolus

nuclear envelope

nuclear lamina

nuclear pores

A

B

C

D nuclear pores

It serves as a barrier that prevent macromolecules from diffusing freely between the nucleoplasm and cytoplasm.

nuleolus

nuclear envelope

nuclear lamina

nuclear pores

A

B

C

Dnuclear envelope