1. CELL : THE UNIT OF
LIFE PART 2
BY ASHNI..
GULF ASIAN ENGLISH SCHOOL..

2. PROKARYOTIC CELLS
The word :
Prokaryotes
• PRO means NOT WELL
DEFINED
KARYO means NUCLEUS
• These cells DO NOT have a well
DEFINED NUCLEUS

3. EXAMPLES :

4. DIFFERENCE IN SHAPES

5. …THE CELL…
• The cell is filled with fluid matrix
called
• CYTOPLASM
• The genetic material is not
enveloped by any nuclear membrane, therefore it is
said to be Naked.
• In addition to genomic DNA , bacteria contains small
round DNA’s called
• PLASMIDS.

6. CELL ENVELOP
Cell envelop is very complex in
bacterial cells.
Glycocalyx (outermost)
-Plasma membrane
- Cell wall
Although they perform different
functions , they together are known
e are mainly three layers
- as SINGLE PROTECTIVE UNIT

7. Bacteria on the basis of response to
staining procedure developed by Gram
viz , can be divided into :
- Gram positive
Bacteria which take up the gram stain.
- Gram negative
Bacteria which do not take up the
gram stain.

8. Different Layers

9. Mesosome

10. What are the Advantages Of
Mesosme ??
- Formation
of cell wall
- Replication of DBA
- Distribution of Daughter cells
- Respiration & Secretion
- Increase surface Area of Plasma
Membrane

11. Prokaryotes such as Cyanobacteria has
membranous extensions into cytoplasm called
CHROMATOPHORES which contain pigments.
Bacterias can be Motile or Non motile ,
depending on the presence of Flagella , Pili
PILI
Flagella
FLAGEL
LA

12. Flagella ?!
- These are the filamentous extensions from cell
wall and has mainly 3 parts :
- Hook – Basal Body – Filament
Pili ?!
- These are elongated tubular made of proteins
Fimbria ?!
- Small bristle like fibres sprooting out of the cell

13. Ribosomes and Inclusion Bodies
In prokaryotes , ribosomes are associated
with plasma membrane.
The size ranges from 15nm to 20nm ,
and has two subunits – 50S and 30S units
which together form 70S.

14. Ribosomes are the site for the synthesis of
proteins.
Several Ribosomes may attach to a single
Mrna and form a chain called
POLYRIBOSOMES or POLYSOME
-- translate the Mrna into proteins.

15. Inclusion Bodies
Reserve material in prokaryotic cells are
stored in the form of INCLUSION
BODIES.
These are not bounded by any membrane
system and lie free in cytoplasm.
Gas vacuoles are found in blue green and
purple and green photosynthetic
bacteria.

16. Eukaryotic Cells
These organisms have an organised
nucleus with a nuclear envelop.
It has organelles and is filled with fluid
called CYTOPLASM
In addition, they hve a variety of complex
locomotory & cytoskeleton structures.
Genetic materials are organised into
CHROMOSOMES

17. EXAMPLES

18. PLANT CELL & ANIMAL CELL

19. CELL MEMBRANE
PROTIENS CARBOHYDRATE
CHAINS
LIPID
BILAY
ER
PHOSPHOLIPIDS

20. Cell Membrane
It is composed of lipids that are arranged in a
bilayer.
The lipids are arranged within the membrane with
the polar head towards the outer sides and the
hydrophobic tails towards the inner part.
This ensures that the nonpolar tail of saturated
hydrocarbons is protected from the aqueous
environment.
The lipid component of the membrane mainly
consist of
PHOSPHOGLYCERIDES

21. The cell membrane also consist of protein
and carbohydrate.
The ratio of protein and lipid varies
considerably in different cell types.
In human being, the membrane of
erythrocyte has approximately 52% protein
and 40% lipids.
Depending on the ease of extraction,
membrane proteins can be classified as
integral or peripheral.
Peripheral proteins lie on the surface of
membrane while the integral proteins are
partially or totally buried in the membrane.

22. Fluid Mosaic Model

23. According to this , the quasi fluid
nature of lipid enables lateral
movement of proteins within the
overall bilayer.
The fluid nature of the membrane is
also important from the point of
functions like
Cellular growth
Formation of intercellular junctions
Secretion, endocytosis , cell division
etc.

24. Functions of Plasma Membrane
The membrane is selectively permeable to some
molecules present on either side of it.
Many molecules can move breifly across the
membrane without any requirement of energy
Passive transport.
Neutral solutes may move across the membrane
by the process of simple diffusion along the
concentration gradient , i.e , from higher
concentration to lower.
Water may also move across this membrane from
higher to lower concentration .

25. Movement of water by diffusion is
called
Osmosis
A few ions or molecules are
transported across the membrane
against the concentration gradient ,
i.e frm the lower to higher
concentration , such a transport is
an energy dependent process , in
which ATP is utilised and is called
Active transport.