The endoplasmic reticulum is a network of folded membranes found throughout the cytoplasm of eukaryotic cells. It was first observed in 1945 by Albert Claude using an electron microscope. The endoplasmic reticulum is divided into two subcompartments: the rough endoplasmic reticulum, which is studded with ribosomes, and the smooth endoplasmic reticulum, which lacks ribosomes. The rough endoplasmic reticulum is the site of protein synthesis and transports proteins throughout the cell, while the smooth endoplasmic reticulum is involved in lipid and steroid metabolism.

1. DONE BY :-
S.Durgashree
IX-A
KENDRIYA VIDYALAYA
KARAIKUDI

2. 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.”

3. Rough ER appears as lumpy sheets of folded
membranes. The lumps are the ribosome. They
are not permanently attached, adhering only
when there is protein manufacturing work to
be done.
Smooth ER which isn't coated with ribosome's
looks like smooth tubes.

4. No specific base or point in a cell, as it extends
a network of membranes, tubules vesicles, and
sacs throughout the cell.
 ER membranes are folded and stacked on top
of each other and connected to the nucleus.
Rough ER with ribosomes attached is closest
to the nucleus.

5. Endoplasmic - “within the cytoplasm”.
Reticulum - Latin for “a little net”.
-> Extensive network of folded membranes that
extends from the nuclear envelope to which it
is connected, throughout the cytoplasm.
-> Divided into two sub-compartments, rough
ER and smooth ER.

6. -> Defined by the presence of ribosomes bound
to its cytosolic surface.
-> Typically composed of a network of flattened
sacs (cisternae).

7. ->Continuous with the outer
membrane of the nuclear
envelope, which also bears
ribosomes on its cytosolic
surface.

8.  Secrete large quantities of proteins, such as
the :
(a) Acinar cells of the pancreas

9. (b) Mucus secreting cells of the lining of the
digestive tract.

10. Rough ER is the starting point of the
biosynthetic pathways of:
 Proteins
 Carbohydrate chains
 Phospholipids
that journey through the membranous
compartments of the cell.

11. Lacks associated ribosomes.
Membranous elements are highly curved and
tubular, forming an interconnecting system of
pipelines curving through the cytoplasm.

12. Extensively developed in a number of cell
types, including those of skeletal muscle,
kidney tubules, and steroid-producing
endocrine glands
FIGURE 1. The smooth ER (SER). Electron micrograph of a Leydig cell from
the testis showing the extensive smooth ER where steroid hormones are
synthesized.

13. Synthesis of fatty acids and steroid hormones,
such as estrogens and testosterone.
Detoxification in the liver of a wide variety of
organic compounds, including barbiturates and
ethanol.
Sequestering calcium ions within the
cytoplasm of cells.

14. Ribosomes on its
outer surface.
Not associated with
ribosomes.
Site of synthesis of
proteins destined for
secretion .
Involved in lipid
metabolism.

15.  ON MEMBRANE - BOUND RIBOSOMES:
 a. Secreted proteins
 b. Integral membrane proteins
 c. Soluble proteins in ER, Golgi complex, lysosomes,
endosomes, vesicles and plant vacuoles
 ON FREE RIBOSOMES:
 a. Cytosolic proteins
 b. Peripheral proteins
 c. Proteins transported to the nucleus
 d. Proteins to be incorporated in peroxisomes,
chloroplasts and mitochondria

16. As each protein is synthesized
in the rough ER, it becomes
inserted into the lipid bilayer
in a predictable orientation
determined by its amino acid
sequence. This orientation is
maintained throughout its
travels in the endomembrane
system, as illustrated in this
figure.

17. I hope that you would
have gained knowledge
from this power point
presentation….