cell biology topic transport across cell membrane. transport of important structures accross plasma mebrane of different types of cell in humans. structure and function of cell membane

1. TRANSPORT ACROSS CELL
MEMBRANE
By Shlok Mathur

2. ABOUT CELL MEMBRANE..
•All cells have a semipermeable membrane bounding the cytoplasm
and the organelles.
•This semipermeable membrane is called cell membrane.
•Functions :
1. It controls what enters and exits the cell body and maintains an
internal balance called Homeostasis.
2. Provides protection and support for the cell.

3. STRUCTURE OF CELL MEMBRANE..
oThe cell membrane has 2 layers of
phospholipids. This layer is
combined and called as a lipid
bilayer. It contains the following
features :
1. Phosphate group is polar or
Hydrophilic.
2. Fatty acid tails is non-polar or
Hydrophobic.
oCell membrane has pores in it which
makes the membrane
semipermeable.
oThe membrane is embedded with
various proteins which help in
transport of substances or
molecules across the cell membrane.

4. TRANSPORT MECHANISM ACROSS
MEMBRANE..
Active process ..
1. Primary Transport
2. Secondary Transport
Passive process ..
1. Simple Diffusion
2. Facilitaded Diffusion
3. Osmosis
4. Bulk flow
5. Filteration

5. DIFFUSION..
• Simple Diffusion : Passive flow of
solute from higher to lower
concentration. It is limited by Thermal
Agitation, Concentration Gradient, and
Solubility.
• Facilitated Diffusion : passive transport
of fluid from higher to lower
concentration mediated by specific
transporter and ion channels.
The transport mediators maybe
Specific Proteins
The transport maybe :
1. Uniport
2. Symport
3. Co-transport

6. OSMOSIS..
o Osmosis is a process of moving of
water across a semipermeable
membrane towards ion or solute rich
region in a solution.
o The pressure that can prevent the
movement of water from another
region which is partitioned by the
permeable membrane is called osmotic
pressure.

7. BULK FLOW..
The movement of large number of ions, molecules or particles
dissolved or carried in a medium such as a fluid or air is called Bulk
Flow.
Rate of bulk flow is determined by the difference of the hydrostatic
pressure of air.
Example :
1. Flow of blood within vessels.
2. Movement of air into and out of the lungs.

8. PRIMARY ACTIVE TRANSPORT.
oPrimary active transport is the
transport of substance uphill
using energy.
oIt causes a conformational
changes that results in transport
of the molecules through the
proteins.
oExamples : Na – K ATPase Pump
Functions :
1. It helps in maintaining high
k+ and low Na+ concentration
inside the cell.
2. It maintains intracellular
negativity.
3. Maintains red blood cell
volume.
4. Activate the carrier proteins.

9. WORKING OF NA –
K ATPASE PUMP..
 The cell membrane contains various Ion Gated
protein channels that help in movement of
Sodium and Potassium ions to move out and
inside of the cell respectively.
 Firstly 3 sodium ions from the cytoplasm attach
to the ion gated sodium channels and use ATP to
close the gate and open on the outside to
release the sodium ions in the extracellular
matrix.
 Then 2 potassium ion attach to the potassium
gated ion channels and use ATP to help in
releasing the ion in the intracellular matrix.
 This process helps in maintain the slight
negativity of the cell.
 Similar to the Na – K pump there are various
other pump such as Ca – H pump , H – K pump ,
etc.

10. SECONDARY ACTIVE TRANSPORT..
oThe transport of substance across cell membrane against
concentration graidient involoving energy to establish a gradient the
membrane, utilize the gradient to transport a molecule of interest up
its concentration gradient.
oThe transport maybe :
1. In the same direction ( Symport )
2. In opposite direction ( Antiport )

11. SYMPORT/ ANTIPORT/ UNIPORT

12. CO – TRANSPORT..
oTransport of two substances using the energy produced by
concentration difference developed by primary active transport.
oSubstances are moving in the same direction.
oExample : transport of glucose, amino acides, transport inside the
actin and myosin filament is also an example of Co – transport.

13. THANK YOU.. Doubt ?