2. What is Endoplasmic Reticulum?
Endoplasmic - “within the
cytoplasm” .Reticulum - Latin for
a “a little net”.
•extensive network of folded
membranes that extends from
the nuclear envelope to which it
is connected, throughout the
cytoplasm. It is present in both,
animal and plant cells.
• divided into two sub-
compartments,
1) Rough Endoplasmic Reticulum
2) Smooth Endoplasmic
Reticulum
3. Discovery of Endoplasmic Reticulum
• discovered by Belgian
biologist Albert Claude
(1899-1983).
• used the newly developed
electron microscope to explore
the interior of cells and along
with his associate Keith Porter
in 1945 observed the presence
of a “lace-work structure.”
4. Structure Of Endoplasmic Reticulum
• Physical Structure:
The Endoplasmic Reticulum is 3-dimensional network
of intracellular. It is formed of three types of element:
1-Cisternae
2-Tubules
3-Vesicles
Cisternae:
- These are flattened , unbranched, sac-like element.
- They lie in stacks parallel to one another.
- They bear ribosomes on the surface
5. Tubules:
-These are irregular branching element
which form a network along with other
element.
-These are often free of ribosomes.
Vesicles:
-These are oval and rounded ,vacuole like
element.
- These are also free of ribosomes.
6.
7. • Molecular structure:
The membrane of ER are composed of two
layers of phospholipids molecules
sandwiched by two layers of proteins
molecules like other membrane in the cell
wall.
• Endoplasmic Matrix:
The space inside the tubules and vesicles is
filled with a watery medium that is different
from the fluid in the cytosol outside the ER.
8. Location of Endoplasmic Reticulum
• There is no specific base or point in a cell,
as it extends a network of membranes,
tubules, vesicles, and sacs throughout the
cell.
• Endoplasmic Reticulum membranes are
folded and stacked on top of each other
and connected to the nucleus.
9. Types of Endoplasmic Reticulum:
• There are two sub- compartments of
Endoplasmic Reticulum on the basis of
Ribosome, their specific functions and their
specific appearance:
- Smooth Endoplasmic Reticulum:
Ribosomes are ABSENT.
- Rough Endoplasmic Reticulum: Ribosomes
are PRESENT.
10. Rough Endoplasmic Reticulum:
• Rough ER- is termed rough
because it is studded with
ribosomes (the molecules where
proteins are made).
• This is an extensive organelle
composed of a greatly convoluted
but flattish sealed sac (cisternae)
that is continuous with the nuclear
membrane.
• In Rough Endoplasmic Reticulum
site of synthesis of proteins is
destined for secretion.
11. Functions of Rough Endoplasmic
Reticulum:
• The rough endoplasmic reticulum
manufactures membranes and
secretory proteins .
• In certain leukocytes (white blood
cells), the rough ER produces
antibodies .
• In pancreatic cells, the rough ER
produces insulin.
12. • The rough and smooth ER
are usually interconnected and
the proteins and membranes
made by the rough ER move
into the smooth ER to be
transferred to other locations.
•
Ribosomes on the rough
endoplasmic reticulum are
called ‘membrane bound’
and are responsible for the
assembly of many proteins.
This process is called
translation.
13. • The membrane of the rough endoplasmic
reticulum forms large double membrane
sheets that are located near, and
continuous with, the outer layer of the
nuclear envelope.
• It helps in protein translocation, Protein
translocation is the process by which
peptides are transported across a
membrane bilayer.
14. • Rough Endoplasmic Reticulum is the
starting point of the biosynthetic pathways
of:
proteins
carbohydrate chains
phospholipids
that journey through the membranous
compartments of the cell.
15. Smooth Endoplasmic Reticulum
• Smooth ER is more
tubular than rough ER.
• Forms a separate sealed
interconnecting network.
• It is found fairly evenly
distributed throughout the
cytoplasm.
• It is not studded with
ribosomes hence ‘smooth
ER’.
16. Functions of Smooth Endoplasmic
Reticulum:
• The network of SER allows increased surface
area for the action or storage of key enzymes
and the products of these enzymes.
• The agranular endoplasmic reticulum is the
site of lipid synthesis (including oils,
phospholipids and steroids)
• It helps in metabolizing of carbohydrates.
17. • It maintains regulation of calcium
concentration.
• In brain cells it synthesizes male and
female hormones.
• In skeletal and cardiac muscle, smooth ER
is modified to form sarcoplasmic reticulum
i.e. in muscle cells SER stores Ca ions
and is known as sarcoplasmic reticulum.
18. • SER also help in the biogenesis of Golgi
complex n lysosomes.
• Moreover, it helps in detoxification of
drugs and poisons. Which is an important
function.
• It serves as a transitional area for vesicles
that transport Endoplasmic Reticulum
products to various destinations.
19. • The network of smooth endoplasmic
reticulum allows for an increased surface area
to be devoted to the action or storage of key
enzymes and the products of these enzymes
• It helps in muscle contraction mechanism.
21. Diseases caused by malfunctioning
of Endoplasmic Reticulum:
ENDOPLASMIC RETICULUM STRESS:
The endoplasmic reticulum (ER) is a
multifunctional organelle required for lipid
biosynthesis, calcium storage, and protein
folding and processing. A number of
physiological and pathological conditions, as
well as a variety of pharmacological agents, are
able to disturb proper ER function and thereby
cause ER stress, which severely impairs
protein folding and therefore poses the risk of
proteotoxicity.
22. Proteotoxicity in Endoplasmic Reticulum
can cause following diseases in organisms:
- Obesity
- Diabetes
- Oestiogenisis
- Aging
