It encloses a brief understanding of transportation, its models and different processes likewise, Active and passive transport and their respective mechanisms, i.e. diffusion, osmosis, exocytosis, aquaporins etc.

1. TRANSPORT MECHANISM AND THEIR
MODELS
Presented By : -
Pragati ( 191512 )
M.Sc. ( Biotech. )
Department of Biotechnology

2. INTRODUCTION
TO CELL
MEMBRANE : -
 The cell membrane( also called plasma
membrane or plasmalemma ) is a biological
membrane separating the interior of a cell from
the outside environment.
 It appears in thin sections with the electron
microscope as a triple- layered structure about
7.5-10 nm thick.
 Term coined by C. Naegeli and C. Cramer in
1855' and plasmalemma coined by J.Q. Plowe in
1931.
Chemical composition of cell membrane : -
 Lipids.
 Proteins.
 Carbohydrates.
 Phospholipids.
 Membrane cholesterol.

3. DIFFERENT
BONDS
INVOLVED
IN CELL
MEMBRANE
: -
 Covalent bond.
 Peptide bonds.
 Disulfide bonds.
 Non- covalent bond.
 Hydrogen bond.
 Hydrophobic interactions.
 Electrostatic / ionic bond.
 Vander Waal's interactions.

4. FUNCTIONS
OF PLASMA
MEMBRANE :
-
 Keeps a cell intact.
 Protective barrier.
 Regulate transport in and out of cell ( selectively
permeable ).
 Provide anchoring sites for filaments of
cytoskeleton.
 Provide a binding site for enzymes.
 Interlocking surfaces bind cells together (
junctions).
 Contains the cytoplasm ( fluid in cell ).
 Small lipid soluble molecules e.g.; O2 and CO2 can
pass easily.
 Water can freely across the membrane.
 Ions and large molecules cannot across without
assistance.
 Allow cell recognition.

5. TRANSPORT MECHANISM : -
 Transport across cell membrane is classified into 4 ways : -
 Diffusion ( Passive Transport ).
 Osmosis.
 Active Transport.
 Vesicular Transport.
 It is the net movement of a substance ( liquid or gas ) from an area of higher concentration to lower
concentration without expenditure of energy is called diffusion.
 Diffusion can be further as followed : -
 Simple diffusion.
 Facilitated diffusion.

6. SIMPLE DIFFUSION :
-
 This means that kinetic movement of molecules or
ions occurs through a membrane opening or
through intermolecular spaces without any
interaction with carrier proteins in the membrane.
 Simple diffusion of lipid soluble substances can take
place through the lipid bilayer, its rate dependent
on how highly lipid soluble it is ( e.g. oxygen,
carbon dioxide, nitrogen, alcohol ).
 The protein channels involved in simple diffusion
are distinguished by 2 important characteristics;
 They are often selectively permeable to certain
substances.
 Many of the channels can be opened or closed by
gates.

7. FACILITATED
DIFFUSION : -
 It is also called carrier mediated diffusion.
 Highly charged or big molecules which cannot pass
through protein channels require carrier protein which
facilitates the diffusion.
 The carrier protein is selective for that particular
substance.
 When a substance to be transported binds to a carrier
protein on one side there is conformational change in the
shape of the protein which carries the substance to the
interior of the cell by opening to other side of membrane.
 It also obeys the law of diffusion ( higher to lower
concentration).
 e.g. glucose transporters ( GLUT ) and amino acid
transporters.

8. OSMOSIS : -
 Each compound obeys the law of
diffusion.
 Diffusion of water from high
concentration of water to low
concentration of water.
 Across a semi- permeable membrane.
 However, some compounds are unable
to across the cell membrane (glucose,
electrolytes... )
 Water can cross will enter or exit the cell
depending on its concentration gradient.

9. AQUAPORINS :-
• The aquaporins are a family of
small membrane- spanning
proteins ( monomer size ~30 kDa )
that are expressed at plasma
membranes in many cells types
involved in fluid transport.
• Aquaporins appear to assemble in
membranes as homo tetramers in
which each monomer, consisting of
six- membrane spanning alpha-
helical domains with
cytoplasmically oriented amino and
carboxy termini.

10. ACTIVE TRANSPORT :
-
o When a substance moves across the cell membrane
against concentration or electrical gradient( uphill ) with
the expenditure of energy it is called active transport. The
energy is obtained from the breakdown of high energy
compounds like ATP.
o The transporter involved here is also carrier protein. Here
the carrier protein is capable of imparting energy to the
transported substance to move against gradient.
 Primary Active Transport : -
• In the primary active transport, the energy is liberated
directly from the breakdown of ATP and the carrier
protein involved here is called as pump. The enzymes
which catalyze the hydrolysis of ATP are called ATPases.
• e.g. NA+/ K+ pump present especially in all excitable cells.

11. SECONDARY ACTIVE
TRANSPORT : -
• When energy is derive secondarily from energy that has been
stored in the form of ionic concentration differences of
secondary molecular or ionic substances between two sides of a
cell membrane, created originally by primary active transport.
• It is of two types : -
 Uniport Transport : -
• It refers to the process which allows the movement of one type
of molecules in only one direction, e.g. glucose uptake in
erythrocytes.
 Cotransport : -
• It refers to the process where transfer of one solute depends on
the simultaneous transfer of the other.
• Two type of molecules when move in the same direction, it is
called as SYMPORT, e.g. the Na+/glucose transport.
• Two types of molecule when move in the opposite direction, e.g.
the Na+/K+ transporter.

12. VESICULAR
TRANSPORT : -
 It is a mode of transport by which large particles
are transported between the ECF and the ICF by
being wrapped in a membrane – enclosed
vesicle. It is of two types : -
1. Endocytosis : - involves the entry into the cell of
materials that are too large to get in by the mere
diffusion.
o It is of two types : -
 Phagocytosis : - it is the process by which a cell
engulf or takes in solid particles that are too
large to enter the cell by diffusion.
 Pinocytosis : - is the process of taking in fluids by
cells.

13. EXOCYTOSIS : -
• It is the reverse of endocytosis, is the
process by which a cell expels large
molecules, such as proteins and
polysaccharides.
• This is where a cell discharges the contents
of a vesicle exterior to the cell.
• Suffering may be wastes product such as
proteins, hormones, etc. For secretion.
• Demands for energy.
• Example : vesicles from the Golgi fuse with
the plasma membrane and the proteins are
discharged exterior to the cell.

14. CONCLUSION : -
 Cell membrane is the separation of the cellular components between
outside and inside.
 There are different bonds are present into the cell membrane which
stabilizes this membrane.
 Cell membrane have different functions like protection, provide flexibility
etc. For transport of the materials from one cell to another. Cell have
many transport mechanism like; diffusion, osmosis, active transport and
vesicular transport.

15. REFERENCES : -
 https://www.studyread.com/cell-membrane-transport-types
 https://www.slideshare.net/Kalavanisathishr/transport-mechanism
 https://en.wikipedia.org/wiki/membrane_transport
 Life.nthu.edu.tw/~b830473/transmechanism.html

16. THANK YOU