Cell biology ppt-2.pptx99999999987788888

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1. CELL BIOLOGY COURSE CODE:ZOOL-304 Topic :Exocytosis And Endocytosis Submitted to:Mam Iqra Jabeen Prepared by:Saman Hayat Degree :BS Zoology (2nd semester )

2. Contents : Introduction Exocytosis Mechanism Types Example Endocytosis Mechanism Types Example Summary

3. Introduction : Endocytosis and Exocytosis are the bulk transport mechanisms used in eukaryotes . As these processes require energy they are termed as active transport processes . Endocytosis and Exocytosis are the processes by which cell moves materials into and out of the cell that are too large to directly pass through the lipid bilayer of the cell membrane.

4. Exocytosis : Exocytosis is the process by which cell moves materials from within the cell into extracellular fluid . Exocytosis occur when a vesicle fuses with the plasma membrane ,allowing its contents to be released outside the cell. It is a vital process of plant and animal cell because it perform opposite of endocytosis. Cell create waste or toxins that must be removed from the cell to maintain the homeostasis.

5. Mechanism : .Exocytosis involves the following mechanism : A vesicle is formed ,typically within the endosplasmic reticulum and the Golgi apparatus or early endosome. The vesicle travels to the cell membrane . The vesicle fuses to plasma membrane ,during which the two bilayers merge. The vesicle ‘contents are released into the extracellular space. The vesicle either fuses with or separates from the cell membrane.

6. Types : There are three types of Exocytosis : Regulated Exocytosis Constituted Exocytosis Lysosome Mediated Exocytosis

7. Regulated Exocytosis : The process of fusion of membrane of cytoplasmic organelles with the plasma membrane which occurs in response to stimulation is regulated exocytosis. Released molecules are known as regulated exocytosis because the released molecules are regulated by extracellular signals and cause membrane depolarization.

8. Constitutive Exocytosis : Constitutive exocytosis is the most common pathway performed by the body cells which do not require extracellular signaling . Some exocytotic vesicle remains in the plasma membrane even after exocytosis but other releases their content and returns to the interior of the cell. This mechanism is termed as the “kiss -and -run”pathway.

9. Lysosome Mediated Exocytosis : Lysosome mediated exocytosis is a process of fusion of cell vesicles and cell lysosome . An enzyme contained in the lysosome breaks down the molecules and carries them into the cell membrane where it fuses and clear out.

10. Example : The white blood cells engulfed a foreign pathogen. Certain parts of the pathogen are no needed more, so they are excrete out through exocytosis. Releasing a neurotransmitter for cellular communication is another example of exocytosis.

11. Endocytosis : The process by which cell takes in the actively transporting molecules from the external surrounding into the vesicles by engulfment process. It occurs when the cell membrane folds engulfing the molecules with extracellular fluid which breaks off vesicles facilitating to transport inside the cell.

12. Mechanism : Following steps are followed during phagocytosis : A particle binds to the receptor on the cell‘s surface ,stimulating the release of pseidopodia . Pseidopodia surrounds the object untill there membrane fuse,forming a phagocytic vesicle The phagocytic vesicle pinches off the cell membrane ,entering the cell membrane The phagocytic vesicle fuses with the lysosomes ,which recycle or destroy the vesicle contents.

13. Mechanism : Following steps are followed during pinocytosis.: Molecules bind with receptors located along the surface of the cellular membrane. The plasma membrane folds in forming the pinocytic vesicle that contains the molecules and the extracellular fluid. The vesicle detaches from the cell membrane inside the cell . The vesicle fuses with early endosome where the contents found within are sorted.

14. Types : There are three types of endocytosis : Phagocytosis Pinocytosis Receptor mediated endocytosis

15. Phagocytosis : Phagocytosis is the process by which cell targets the large molecules that are not particularly specific . It is also known as the cell eating process and how the immune cells and white blood cells like macrophage and neutrophil engulfs and destroy pathogen and toxic ccompounds.

16. Pinocytosis : In the pinocytosis process, the cell takes in small substances like water and nutrients from the extracellular fluid and is non -specific. It is also known as cell drinking process which is common in plant and animal cells.

17. Receptor Mediated Endocytosis : Another specialized type of endocytosis is receptor mediated endocytosis where macromolecules require specific receptors to bind on the cell membrane surface. One of the common example of receptor mediated endocytosis is cholesterol uptake in body.

18. Examples : White blood cells engulfing a virus and eliminating it is an example of endocytosis. Cholesterol uptake in body is also an example of endocytosis.

19. Summary : Endocytosis is the process of capturing a substance or particle from outside the cell by engulfing it with the cell membrane and bringing it into the cell. Exocytosis is the process of fusion of vesicles with plasma membrane and releasing the contents outside the cell. Both Endocytosis and Exocytosis are the processes of active transport.