Its all about endoplasmic reticulum..Chapter:-Cell structure and function

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