Description of the process of bulk transport, different types of receptors etc.

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SEMINAR PRESENTATION ON
BULK TRANSPORT: RECEPTOR MEDIATED ENDOCYTOSIS
Presented by:
PARAG PATGIRI
M. Sc.
Department Of Zoology
BODOLAND UNIVERSITY
Guided by:
Dr. ANANTA SWARGIARY
Asst. Professor
Department Of Zoology
BODOLAND UNIVERSITY

2. CONTENTS
1. INTRODUCTION
2. EXOCYTOSIS
3. ENDOCYTOSIS
 PHAGOCYTOSIS
 PINOCYTOSIS
 RECEPTOR MEDIATED ENDOCYTOSIS
4. CONCLUSION
5. REFERENCES
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3. INTRODUCTION
Bulk Transport
When a molecules are too large to move through a channel protein or
by carrier protein , vesicles are used to move the bulk molecules.
Bulk transport of substances are accomplished by:
Endocytosis: Movement of substances into the cell
 Phagocytosis: Ingestion of large particles such as microorganisms
via large vesicles, Phagosomes
 Pinocytosis: Ingestion of fluid and solutes via pinocytic vesicles
e.g.: LDL
Exocytosis: Movement of materials out of the cell
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4. Bulk
Transport
Endocytosis
Phagocytosis
Pinocytosis
Exocytosis
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5. EXOCYTOSIS
• Occurs when materials discharge from the cell
• Vesicle in the cytoplasm fuse with the cell membrane and release
their content to the exterior of the cell
• Used in animals to secrete hormones, neurotransmitters, digestive
enzymes etc.
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Fig: Exocytosis

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ENDOCYTOSIS
• The routes that lead inward from
the cell surface to lysosome.
• Take up macromolecules, particular
substances and in specialized cases
even other cells.
• The material to be ingested is
progressively enclosed by a small
portion of the plasma membrane.
• First invaginates and then pinches
off to form an endocytic vesicle
containing the ingested substance
or particle.
Fig: Route of Endocytosis

7. PHAGOCYTOSIS (CELL EATING)
• The bulk transport of large molecules or whole cells into the cells.
• Ingest particles by forming phagosomes, having >250nm diameter.
• Macrophages, a WBC engulf entire bacteria, which eventually
encloses them in a vesicle within the cell cytoplasm.
Fig: Phagocytosis
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8. PINOCYTOSIS ( CELL DRINKING)
• The bulk transport of large amount of small solutes or extracellular
fluid into vesicles in the cell, forming a pinocytic vesicle
• Vesicle is about 100nm in diameter
• Uptake of soluble material dissolved in extracellular fluid selectively
as well as non selectively
• Selective and efficient uptake occurs when solutes are captured by
specific high affinity receptors, receptor mediated endocytosis
• After pinching off, vesicles undergo via endosome to lysosome and
hydrolysed.
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9. Fig: Pinocytosis
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10. RECEPTOR MEDIATED ENDOCYTOSIS
• Macromolecules bind to complementary transmembrane receptor
proteins, accumulate in coated pits, and then enter the cell as
receptor–macromolecule complexes in clathrin - coated vesicles
• When a cell needs cholesterol for membrane synthesis, it makes
transmembrane receptor proteins for LDL and inserts them
Fig: LDL receptors binding to a coated pit in the plasma membrane
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Fig: Assembly and disassembly of a clathrin coat

12. Fig: The receptor-mediated endocytosis of LDL
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13. • As receptors are ligand specific, receptor-mediated endocytosis provides
a selective concentrating mechanism that increases the efficiency of
internalization
• LDL particles bound to LDL receptors in the coated pits are rapidly
internalized in coated vesicles
• After shedding their clathrin coats, the vesicles deliver their contents to
early endosomes
• At low pH, LDL is released from its receptor and is delivered via late
endosomes to lysosomes
• Cholesteryl esters in the LDL particles are hydrolyzed to free cholesterol
• After dissociates from its ligand in the early endosome receptor is
recycled back to the plasma membrane for reuse
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14. CONCLUSION
Plasma membrane is a dynamic structure that functions to
segregate the chemically distinct intracellular milieu from the
extracellular environment by regulating and coordinating the entry and
exit of small and large molecules. So that molecules must be carried
into the cell by the process Endocytosis and secretion must be carried
out by the process Exocytosis. Receptor mediated Endocytosis is
important as it is ligand specific and increases the efficiency of
internalization.
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15. REFERENCES
1. Bruce Albert, Alexander Johnson, Julian Lewis, Martin Raff, Keith
Roberts, Peter Walter. Molecular Biology Of the Cell. 5th Edition.
2008.
2. Pranav Kumar, Usha Mina. Life Science: Fundamentals and Practice-
1. Pathfinder Publication. 7th Edition. 2021.
3. https://www.google.com/imgres?imgurl=https%3A%2F%2Fi0.wp.c
om%2Forbitbiotech.com%2Fwp
4. https://www.google.com/imgres?imgurl=https%3A%2F%2Fi0.wp.c
om%2Forbitbiotech.com%2Fwp
5. https://www.google.com/imgres?imgurl=https%3A%2F%2Fars.els-
cdn.com%2Fcontent%2Fimage%2F3-s2
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THANK YOU