This presentation consists of the fluid mosaic model, tight junction and cytoskeleton

1. FLUID MOSAIC MODEL OF CELL MEMBRANE
TIGHT JUNCTION
CYTOSKELETON
BY – ARUSHI PAL
*

2. *The fluid mosaic model was first proposed by S. J
SINGER and GARTH L. NICLSON in 1972 to explain
the structure of the plasma membrane
.
*WHAT IS FLUID MOSAIC MODEL ?
The fluid mosaic model describe the cell membrane as
a tapestry of several types of molecules ( phospholipid ,
cholesterol , and protein) that are constantly moving .
This movement helps the cell membrane maintain its role
as a barrier between the inside and outside of cell
membrane.

3. *Points regarding on FMM :
*The study of fluid mosaic model is clearly
studied after electron microscope .
*It composed of lipid bilayer, lipid are fatty
acid

4. Hydrophobic tail – present inside
Hydrophilic head – present outside , because
to prevent hydrophobic tail from aqueous
enviroment
lipid component mainly consist of
phosphoglyceride
they also contain protein and
carbohydrate.
RBC 52% protein and 40% lipids
there are two types of protein

5. *Integral protein
*Peripheral protein
*Integral protein – protein are on the buried
area.
*Peripheral protein – protein are on the surface
area.

7. *
*TRANSPORT
PASSIVE OSMOSIS
ACTIVE
1- PASSIVE- If any molecule from this lipid
bilayer, transport or travel without any energy
called passive transport. Means no ATP is
required.

8. *2 – ACTIVE
if any molecules from this lipid bilayer transport
or travel with energy called active transport
means ATP is required.
Polar molecules like Na and K
3 – OSMOSIS
Movement of water from high concentration to
low concentration

9. *
*Phospholipid molecules shows two types of
movement :
Transition Flip flop
movement movement
1- Transition movement : movement of
phospholipid molecules in same direction .
2 - Flip flop movement : movement of phospholipid
movement between two layers.

10. TIGHTJUNCTION

11. *
*Tight junction are areas where the membrane of two
adjacent cell join together to form a barrier .
* The cell membrane are connected by strands of
transmembrane protein such as claudins and
occludin.
*Tight junction binds cell together , prevent molecules
from passing in between cell and also helps to
maintain the polarity of cells. They are only found in
vertebrate , animals with a backbone and skeleton

12. *

13. *
*To help cells from a barrier that prevent
molecules from getting through and to stop
protein in the cell membrane from moving around
.
*Tight junction are often found at epithelial cells (
which are cells that line the surface of the body
and line body cavities .)
* not only epithelial cell do separate the body from
the surrounding environment , they also separate
surface with in the body , therefore it is very
important that the permeability of molecules
through layer of epithelial cell is tightly controlled.

14. *if molecules are blocked by tight junction and physically
unable to pass through the space in between cells , they
must enter through other methods that involve entering
the cells themselves.
*They could pass through special protein in the celll
membrane or be engulfed by the cell through
endocytosis.
*Using this method , the cell has greater control over what
material it take in and allow to pass through epithelial cell
, certain protein must be kept on certain sides of the cells.

15. the apical or outside layer of the sheets of cells contains
protein that only let certain substances pass through .
The basal layer or inside layer is where cells let molecules
pass through them by expelling them from their membrane
in a process called exocytosis .
the tight junction keep the correct proteins on the correct
sides of the cells in order to function this also help
maintain the polarity of cell.
Another function is simply to hold cell together . The
branching protein strands of tight junction link adjacent cell
together tightly so that they from a sheet.

16. *
*Tight junction are a branching network of
protein strands on the surface of a cell that link
with each other through out the surface of the
membrane . The strands formed by trans
membrane protein on the surface of the cell
membrane that are adjacent to each other.
* there are about 40 different protein at tight these
protein can be grouped into four main types.
* 1 – trans membrane protein – are wedged in the
middle of the cell membrane and are responsible
for adhesion and permeability

17. *2 – scaffolding proteins – organize transmembrane protein
*3- signaling proteins – are responsible for forming the tight
junction and regulating the barrier
*4 – regulation proteins – regulate what protein are brought to
the cell membrane in vesicle.
*Claudins and occludin – are the two main types of protein
present at tight junction and they are both transmembrane
protein
*
* claudins – are important in forming tight junction
*Occludin – play more of a role in keeping the tight junction
stable and maintaining the barrier between cell that’s keeps
unwanted molecules out .

18. *Other cell junction :
*Other cell junction are gap junction and anchoring junction
*1 – gap junction – are channels in cells that let adjacent cell
communicate with one another without having to send
molecules through ECF surrounding the cell.
*2 - anchoring junction – hold cell together with anchoring
protein such as catenins and cadherins . The cell cytoskeleton is
tethered to proteins that link adjacent cell.
*
* a type of cell junction in which cells are connected by a mass
of protein ( anchoring junction )
* a types of cell junction that allows adjacent cell to exchange
molecule ( gap junction )

20. *
*The cytoskeleton is responsible for cell shape ,
motility ( movement ) of the cell as a whole and
motility of organelles with in a cells .
*There are the three types of filaments in the
cytoplasm of most vertebrate cells:
* 1- microfilaments
* 2 – microtubules
* 3 – intermediate filaments

21. *
*The thickest are the microtubules ( 20 nm in a
diameter ) which consist primarily of tubulin protein
.
*Each tubulin subunit is a made of one alpha and one
beta tubulin that are attached to each other , so
technically tubulin is a heterodimer not a monomer .
*Since it looks like tube , it is named as microtubule
*It is pipe like structure .
*In a microtubules structure tubulin monomers are
linked both at their ends along their sides ( laterally )
. This means that microtubules have distinct ends ,
called the positive and negative ends

23. *
*Transportation of water , ions or small molecules
.
*Cytoplasmic streaming .
*Formation of fibers or aster of the mitotic or
meiotic spindle during cell division .
*Formation of structural unit of the centrioles
basal granules , cilia and flagella
*

24. *
*Tough and flexible
*The thinnest are the microfilaments ( 7nm in a diameter ) which
are solid and are principally made of two strands of a globular
proteins called actin .
*For this reason , microfilaments are known as actin filaments.

26. *Actin is powered by ATP to assemble filaments from , which
serves as a track for movements of a motor protein called
myosin .
*FUNCTION:
1- they maintain the shape of the cell .
2- From contractile component of cell mainly of the muscles
cell.
3- WBC can move to the site of an infection and engulf the
pathogen due to microfilaments.

27. *
*The of the middle order are called intermediate
filaments 10nm in a diameter .
* they have been classified according to their
constitute proteins such as desmin filaments ,
keratin filaments , neurofilaments and glial
filaments .
*FUNCTION :
* it contribute to cellular structural elements and
are often crucial in holding together tissue like
skin .

29. *
*The cytoskeleton is responsible for lots of
important cellular function :
* providing cell shape .
*It allows cells to move .
*Engulf particles .
*Transport vesicles through cytosol.
*Separate chromosome during cell division.
*It allow our muscles to contract.