1. CELL : THE UNIT OF
LIFE PART 3
BY AISHA…
GULF ASIAN ENGLISH SCHOOL..

2. TOPICS COVERED: CELL WALL
 ENDOMEMBRANE SYSTEM
 ENDOPLASMIC RETICULUM
 GOLGI APPARATUS
 LYSOSOMES
 VACUOLES
 MITOCHONDRIA
 PLASTIDS
 CHLOROPLASTS.

3. CELL WALL
Present only in plants and fungi.
 Consist of primary wall, secondary
wall, middle lamella with calcium
pectate.
FUNCTIONS:
- gives shape and protects the cell from
mechanical damage.
- cell to cell interaction
-barrier to undesirable macromolecules.
 Cell wall of algae consist of cellulose,
galactants, mannans, minerals like
calcium carbonate.
 Cell wall of other plants consist of
cellulose, hemicellulose, pectins and
protiens.
PRIMARY CELL WALL:
-Capable of growth.
- diminishes as the cell matures.

4. Endomembrane system
contains only those
organelles whose
functions are
coordinated.
It consists of:
 Endoplasmic
reticulum(ER)
 Golgi complex
 lysosomes
 Vacuoles

5. Discovered by porter and thompson.
 ER are a network of tiny tubular structures
scattered in the cytoplasm.
 consists of 30-40% of endomembrane system
 ER divides into 2 compartments.
1. luminal(inside ER)
2. extra luminal(cytoplasm)
FUNCTIONS:
1. Mechanical support
2. Conduction of information
3. Intercellular transport
4. Localization of enzyme
5. Large surface area.

6.  ER are of two types:
*Rough ER
 bear
ribosomes
 they are extensive and
continuous
 performs protein
synthesis and secretion
 attached to nuclear
membrane.
*Smooth ER
 does not bear ribosomes
 performs synthesis of
lipid
 In animal cells lipid like
steroidal hormones are
synthesized in SER.
 storage

7.  discovered by Camillo Golgi in 1898.
 found in eukaryotic cells (except mammalian
erythrocytes).
 they are reticular structures near the nucleus.
 consist of cisternae which are flat, disc-shaped
sacs parallel to each other.
 2 faces:- 1. convex cis or the forming face.
2. concave trans or the maturing face.
 FUNCTIONS:1. Packaging materials to be delivered to the
intercellular targets or secreted outside.
2. Protein synthesized by ribosomes are modified
in the cisternae.
3. important site for formation of glycoproteins
and glycolipids.

8. ...
Lysosomes
Lysosomes..
These are membrane bound
vesicular structures.
.
.
 Formed by packaging of golgi
apparatus
 rich in hydrolytic enzymes
 Active at acidic pH
 these enzymes are capable of
digesting carbohydrates, proteins,
lipids and nucleic acids.
 Popularly called “sucide bags “.

9. …VACUOLES…
They are membrane bound
space found in cytoplasm
Contains water, sap, excretory
product and other materials not
useful for plants.
The vacuole is bounded by a
single membrane called
tonoplast.
In Amoeba, contractile
vacuole and in protista food
vacuole.

10.  Sausage-
shaped or cylindrical having diameter of
0.2- 1.o μm and length 1.0 – 4.1 μm.
 They are double membrane-bound structures with
the outer and inner membrane.
 Outer membrane forms continuous limiting
boundary of the
organelle.
 Inner membrane forms infoldings called cristae to
increase surface area.
 They are the sites for aerobic respiration.
 Produce cellular energy in the form of ATP
molecules.

11. Known as powerhouses of the cell.
Divide by fission.
The membranes divide the lumen into 2
aqueous compartments, namely:
1.outer compartment
2.inner compartment called matrix.

12. …Plastids…
Found in plants and euglenoids.
They are large
They contain pigments, imparting colors and storage products.
Plastids can be classified into:
*CHLOROPLAST
*CHROMOPLAST
*LEUCOPLAST
•Contains chlorophyll
•Contains fat soluble •Colorless plastids
and carotenoid
carotenoid pigments •Various shapes and
pigments.
like carotene,
sizes with stored
•Found mainly in
xanthrophylls and
nutrients
mesophyll of leaves .
others are present. •LEUCOPLAST can be
•These are lens
•Found in yellow,
divided into 3:shaped, oval shaped,
orange, red.
1.Amyloplasts –
spherical, discoid or
store carbohydrates
even ribbon-like
2.Elaioplasts –
organelles.
store oils and fats
3. Aleuroplasts –
store proteins.

13.  CHLOROPLAST
Double membrane bound
Inner membrane is less permeable
The space limited by inner
membrane is called stroma
Flattened membranous sacs called
thylakoids are present in the stroma
Thylakoids are arranged in stacks
like piles of coins called grana or
intergranal thylakoids
Flat membranous tubules called the
stroma lamellae
The membrane of thylakoids
enclose a space called lumen.
Stroma contains enzymes required
for the synthesis of carbohydrates
and proteins.
It also contains DNA molecules and
smaller ribosomes.