Cell Wall and Endoplasmic Recticulum

1. Submited to – Submitted by -
Dr. K. K. Panigrahi Kaushal Kumar
Assistant Prof. PBG 2nd yr. B. Sc. (Ag)
Adm no – 01C/15

2. Cell Wall
Introduction:-
 In plants (including bacteria) a cell is always
surrounded by a cell wall lined throughout with
plasma lemma.
 The cell wall is found in plants and is absent in
animals.
 Cell wall is the outermost part of the cell and is
always non-living, though produced and
maintained by living protoplasm.

3.  It originates from the
phragmoplast (phragma =
fence, separation).
 Endoplasmic reticulum, golgi
complex, mitochondria and
microtubules play an
important role in the
formation of the cell wall.
 It is mainly composed of
cellulose. However it may
also contain hemicellulose,
pectin, chitin, cutin and
lignins.

4. The cell wall is complex in
nature and is differentiated into
middle lamella, primary cell
wall and secondary cell wall.
1. Middle lamella: It is the
outmost layer of plant cell
wall and connects the two
adjacent cells. It is
composed of calcium and
magnesium pectate and
does not contain any
cellulose.

5. 2. Primary cell wall: It is thin, elastic and
lies between middle lamella and secondary
cell wall. It is mainly composed of cellulose.
It develops after middle lamella by
deposition of hemicellulose, cellulose and
pectin substances.
3. Secondary cell wall: It is the inner most
layer of cell wall and lies between primary
cell wall and plasma membrane. It is
relatively thick and is primarily composed of
microfibrils of cellulose.

6. Functions:-
1. It determines the shape and size of a cell.
2. It provides protection to the inner parts of a cell
from the attack by pathogens.
3. It provides mechanical support to the tissues
and act as a skeletal framework of plants.
4. It helps in transport of substances between two
cells.

7. Endoplasmic Reticulum (ER):
 The endoplasmic reticulum was first observed by
Porter in 1945 in liver cells of rats.
 Cytoplasmic matrix is transversed by vast
reticulum or network of interconnecting tubules
and vesicles known as endoplasmic reticulum.
 The membrane of endoplasmic reticulum may be
either smooth when they do not have attached
ribosomes or rough when they have ribosomes
attached with it.
 The membrane of endoplasmic reticulum is found
to be continuous with the nuclear membrane and
plasma membrane.

8. The three principle forms
of endoplasmic reticulum
are :
1. Cisternae: Long, flattened,
sac like, unbranched tubules
arranged paralelly in bundles
40-50 mμ in diameter.
2. Vesicles: Oval, membrane
bound, vacular structures, 25-
230 mμ in diameter.
3. Tubules : Branched
structures forming reticulum
system along with cisternae
and vesicles 50-190 mμ in
diameter.

9. Functions:
1. The endoplasmic reticulum forms the ultra
structural skeletal frame work of cytoplasmic
matrix and it provides mechanical support to it.
2. It also acts as an intracellular circulatory
system and it circulates various substances into
and out of the cell by the membrane flow
mechanisms.
3. The endoplasmic reticulum acts as a storage
and synthetic organ. For example: It synthesizes
lipids, glycogen,cholesterol,glyserides, hormones
etc.

10. 4. It acts as a source of nuclear membrane’s
material during cell division.
5. It protects cell from toxic effects by de -
toxification.
6. In certain cases, it transmits impulses
intracellularly. In such cases it is known as
sarcoplasmic reticulum.
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