Exocytosis, endocytosis

1. EXOCYTOSIS:
By
Dr. Harinatha Reddy A
ASSISTANT PROFESSOR
Department of Biotechnology
Christ University
Bangalore

2.  Exocytosis is a form of active transport in which a cell transports
molecules (e.g., neurotransmitters, proteins and waste products)
out of the cell.
 Vesicles containing these membrane components fully fuse with
and become part of the outer cell membrane.

3. EXOCYTOSIS:

4.  In exocytosis, membrane-bound secretory vesicles are carried to
the cell membrane and fuse with cell membrane release their
contents into the extracellular environment.
 In neurotransmission, neurotransmitters are typically released from
synaptic vesicles into the synaptic cleft via exocytosis.

5. Endocytosis:

7. Endocytosis:
 Endocytosis is a form of active transport in which a cell transports
macromolecules into the cell by engulfing them in an energy-using
process.
 Endocytosis and its counterpart, exocytosis, are used by all cells
because most chemical substances important to them are large
polar molecules that cannot pass through the hydrophobic plasma
or cell membrane by passive means.
 Endocytosis includes pinocytosis (cell drinking) and phagocytosis
(cell eating).

8. Phagocytosis:

9.  During phagocytosis cells engulf large particles such as bacteria,
cell debris, or even intact cells.
 Binding of the particle to receptors on the surface of the phagocytic
cell triggers the extension of pseudopodia-an actin-based movement
of the cell surface.
 The pseudopodia eventually surround the particle and their
membranes fuse to form a large intracellular vesicle (>0.25 μm in
diameter) called a phagosome.
Phagocytosis:

10.  The phagosomes then fuse with lysosomes, producing
phagolysosomes in which the ingested material is digested by the
action of lysosomal acid hydrolases.
 During maturation of the phagolysosome, some of the internalized
membrane proteins are recycled to the plasma membrane

11.  Phagocytosis plays distinct roles in different kinds of cells.
 Many amoebas use phagocytosis to capture food particles, such as
bacteria or other protozoans.
 In multicellular animals, the major roles of phagocytosis are to
provide a defense against invading microorganisms and to
eliminate aged or damaged cells from the body.

12.  In mammals, phagocytosis is the function of primarily two types of
white blood cells- macrophages and neutrophils- which are
frequently referred to as "professional phagocytes."
 Endocytosis is Molecule-specific, so it also known as receptor-
mediated endocytosis.

13. Pinocytosis:

14. Pinocytosis:
 Pinocytosis is non-specific and non-absorptive.
 Pinocytosis known as fluid endocytosis.
 Pinocytosis, is a mode of endocytosis in which small particles
suspended in extracellular fluids (Water and soluble salts and so on
) are brought into the cell through an invagination of the cell
membrane.
 Invagination of the cell membrane resulting pinocytotic vesicles
are formed inside the cell.

15.  These pinocytotic vesicles subsequently fuse with lysosomes to
hydrolyze (break down) the particles.
 This process requires energy in the form of adenosine triphosphate
(ATP).

16. Receptor-mediated endocytosis: