Dr. M.M. Khan sir (H.O.D.)
Dr. Indu Ma’am
Dr. Pushpalata Ma’am
Dr. Rashmi Ma’am
Dr. Samreen Ma’am
Dr. Majid Sir
Dr. Sanjeev Sir
Vesicular transport is the special category of Active Transport, But is Independent of
concentration gradient across the cell membrane.
The substances are transported across but NOT THROUGH the Cell membrane in the form
CATEGORIES OF VESICULAR TRANSPORT :
It is defined as the transport mechanism by which the MACROMOLECULES enters the cell.
Macromolecules are very large and thus can’t pass through the cell membrane either by
Active or Passive Transport.
Such substances are transported into the cell by Endocytosis.
TYPES OF ENDOCYTOSIS :
3- Receptor-mediated endocytosis.
It is a process by which Macromolecules are taken into the cell.
It is also called Cell Drinking, because macromolecules are taken along with the
droplets of extracellular fluid in the vesicle.
Events involved in pinocytosis
Macromolecules attach to the surface of cell
Now the cell membrane evaginates around the droplets
and engulf the droplets.
The engulfed droplets are converted to vesicles or
vacuoles called endosomes.
Endosome travel into the interior of cell.
Primary lysosome in the cytoplasm fuses with the
endosome to form secondary lysosome.
Now the Hydrolytic enzymes in secondary lysosome
active resulting in the digestion and degradation of
It is the process in which, particles larger than Macromolecules like Bacteria or
Antigen, are engulf into the cell.
It is also called ‘CELL EATING’.
Only few cells like Neutrophils, monocytes ( WBCs) and Tissue Macrophages
HOW WHITE BLOOD CELLS PERFORM PHAGOCYTOSIS?
White blood cells, Neutrophils and Monocytes are the first line of Defense Mechanism of
the body when any Infection occurs.
So, during any Infection or injury to the tissue, these cells shows the following steps :
1. DIAPEDESIS: leukocytes squeeze out through the narrow blood vessels to reach the
site of infection.
2. AMOEBOID MOVEMENT: Cells shows amoebic movement by bulging out of the
cytoplasm and change in shape.
3. CHEMOTAXIS: It is the attraction of these cells towards the injured tissue by the
chemical substances released at the site of injury.
4. PHAGOCYTOSIS: Neutrophils and monocytes engulf the foreign bodies by means of
EVENTS INVOLVED IN PHAGOCYTOSIS
When a microbe enters the body, first the phagocytic
cell send cytoplasmic extension (pseudopodium) around
Then, these particles are engulfed and are converted
into large Endosome called vacuoles or PHAGOSOMES.
Phagosomes travel into the interior of the cell.
Primary lysosome fuses with phagosome to form
Hydrolytic enzymes in the secondary lysosomes are
activated resulting in the digestion of phagosomal
3. RECEPTOR-MEDIATED ENDOCYTOSIS
It is a transport of macromolecules with the help of a receptor protein.
Surface of the cell membrane has some pits which contain a receptor protein
Each pit with receptor protein called receptor coated pits.
Some receptor protein in cell membrane other than Clathrin are Caveolin which
are concerned with the transport of Vitamins into the cell.
Events involved in receptor-mediated endocytosis
Ligand molecule bind with receptor to form ligand-
Ligand-receptor complex get aggregated in the clathrin
This whole pit detached from the cell membrane and
become coated vesicle (Endosome) in the cytoplasm.
Later, receptor protein detached from the endosome
Endosome fuses with the Primary lysosome to form
Hydrolytic enzymes in the secondary lysosome
activated resulting in the release of Ligand in
It is the process by which substance are expelled from the cell by
means of secretory vesicle.
This is the reverse of endocytosis.
Mechanism of Exocytosis
Secretory substances are stored in the form of secretory vesicle in the cytoplasm.
When required, the vesicle approaches the cell membrane and get fused with it.
Later, the content released out of the cell.
ROLE OF CALCIUM IONS IN EXOCYTOSIS:
Calcium ions play an important role in transmission of impulse at Neuromuscular
When the action potential reaches the axon terminal, the voltage gated calcium
channels open, and calcium enter from synaptic cleft into the axonal bulb
This cause the exocytosis of synaptic vesicle and release of Acetyl choline
(neurotransmitter) into the synaptic cleft.
It is a transport in which extracellular
substance enters the cell through one side
and leaves the cell through the other.
It involves the mechanisms of Receptor-
mediated endocytosis and exocytosis.
But here the protein involve is Caveolin and
EXAMPLE: Movement of protein from
capillary blood into interstitial fluid across the