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Passive Transport

• High -> Low Concentration

• No ATP needed• Towards

equilibrium

1. Simple diffusion2. Facilitated

diffusiona. Transport proteinsb. Ion channels

3. Osmosis

Active Transport• Low -> High

Concentration ie;Against concentration gradient• ATP needed

1. Cell membrane pumpsa. Transport proteinsb. Ion channels

2. Movement in vesiclesa. Endocytosis

- Pinocytosis- Phagocytosis

b. Exocytosis

Modes of fluid transport

Pasteur’s ; Elie

Metchnikoff ,Russian

Zoologist in 1883 first recognized

PHAGOCYTES

TWO PRINCIPAL CLASSES OF PHAGOCYTOSIS

Polymorphonuclear granulocytes (polymorphos)

Produced in bone marrow and discharged into blood50 to 100 billion polymorphousLive for a few days only

Contain numerous enzymeMembrane - bound organelles called LYSOSOMES

MacrophagesPrecursor monocytes (blood cells with horse shoe shaped nucleiLive for a long time

They are not numerous as polymorphous

STEPS

Killing mechanisms of phagocytes. The figure shows the many different techniques used by phagocytes to kill pathogens. Some require oxygen while others do not

Capture of a Yeast Cell (yellow) by Membrane Extensions of an Immune System Cell (blue)

Pinocytosis- sipping.Taking in of liquid droplets by formation of pinocytic vesicles or pinosomes.Vesicles formed are often small( micropinotic vesicles)

-Micro pinocytosis 1st observed by Edwards in amoeba and by lewis in cultured cellsEg: Amoeba

Plasma membrane of such cell invaginates forming a pinocytic channel. The channel is then cut off from the plasma membrane to give a pinocytic vesicle. Lysozome approaches and carries out intracellular digestion as mentioned in phagocytosis.

Key features of Phagocytosis and Pinocytosis

They are bulk transport (i.e. swallowing or drinking) of particles into a cell .They are active process involved expenditure of energy.(ATP)

The particles transported into a cell can be large particles. Some of them can be seen under light microscope.

Intracellular digestion is common accompanying pinocytosis and phagocytosis. Therefore they are associated with the activities of lysozomes.

839 Shivani840 Vishwanath

841 Divesh

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1)Exocytosis involve the movement of macromolecules out of the cell by the fusion of membrane bound vesicles to the plasma membrane

2. Endocytosis [ endo = inside]movement of large materials to INSIDE of the cell by formation of vesicles.ie; membrane may fold inward, trapping materials from the outside