Exocytosis and Endocytosis..pptx in vast

This PPT cover all the processes of topic which simple and lucid language.

1. EXOCYTOSIS & ENDOCYTOSIS

2. Constitutive : Involves secretion of membrane lipids and proteins and their delivery to the cell’s surface & expulsion of cell substances to the exterior. Regulated : relies on the presence of extracellular signals for the expulsion of materials within vesicles. E.g. Secretory cells store hormones, neurotransmitters, and digestive enzymes that are released only when triggered by extracellular signals. Lysosome mediated : Lysosomes carry the digested material to the cell membrane where they fuse with the membrane and release their contents into the extracellular matrix.

3. Illustration of an axon releasing dopamine by exocytosis Illustration of cellular pathways of exocytosis

4. Stages of exocytosis in secretory cells . Formation of vesicles, (b) vesicle “docking,” (c) the transformation of vesicles into fusion-competent vesicles (“priming”), and (d) fusion. Regulated exocytosis requires SNARE machinery (colored lines) and for the ultimate and penultimate steps calcium ions.

5. Steps of Exocytosis (Contd.)

6. Dynamin  is a  GTPase  responsible for  endocytosis  in the eukaryotic cell.  Dynamin itself is a 96  kDa enzyme, and was first isolated when researchers were attempting to isolate new microtubule-based motors from the bovine brain. Dynamin has been extensively studied in the context of clathrin-coated vesicle budding from the cell membrane. During clathrin -mediated endocytosis, the cell membrane invaginates to form a budding vesicle. Dynamin binds to and assembles around the neck of the endocytic vesicle, forming a helical polymer arranged such that the GTPase domains dimerize in an asymmetric manner across helical rungs. The polymer constricts the underlying membrane upon GTP binding and hydrolysis via conformational changes emanating from the flexible neck region that alters the overall helical symmetry.

7. PHAGOCYTOSIS

8. Entry of the pathogen → Phagosomes → Phagolysosomes → Recruitment of Phagocytes → Inflammation

9. Step 1 .  A molecule in the extracellular fluid binds to the cell membrane which begins the pinocytosis process. Step 2.   This triggers the cell membrane to create a fold around the fluid containing the molecules to be ingested. Step 3.   The cell membrane invaginates (folds back on itself) to create a pouch. Step 4 .  This pouch is then pinched off at the cell membrane and can migrate into the cytosol of the cell.