Cell locomotion

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Endocytosis By Dr. Fatima Riaz

Transcript of Cell locomotion

Page 1: Cell locomotion

Endocytosis

ByDr. Fatima Riaz

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Transport across Cell Membrane

• Diffusion is the process of cells moving from areas of high concentration to areas of low concentration.

– This random movement causes the molecules to become evenly spread out.

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Diffusion

• Cells use diffusion to get substances into and out of the cell.– Example: During photosynthesis, oxygen is

produced inside the cell. When this happens the concentration of oxygen becomes higher inside the cell than outside and oxygen diffuses out of the cell.

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• Osmosis is the diffusion of water through a membrane.– Water moves into an area with low concentrations

and out of areas with high concentrations.

• Both diffusion and osmosis are forms of passive transport (they require no energy)

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Transport across Cell Membrane: Active Transport

• materials move from low concentration to high concentration. requires energy!

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Endocytosis

– moving a particle into the cell• Phagocytosis• Pinocytosis

– Exocytosis: moving a particle from inside the cell to outside.

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• PINOCYTOSISIngestion of minute particles e.g protein molecules

• PHAGOCYTOSISIngestion of large particles, such as bacteria, whole cells or portions of degenerated tissue.

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Mechanism of pinocytosis

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Movement thru the Cell Membrane: Active Transport

Endocytosis Exocytosis

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Cell Locomotion

• Amoeboid movement• Ciliary movement

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Ameboid movement

• Movement of an entire cell in relation to its surroundings

• Involves pseudopodium and ATP• Mechanism– formation of new cell membrane & exocytosis at one

end– Attachment of pseudopodium to tissues

• Receptor proteins– Absorption of the membrane & endocytosis in mid &

rear portions– Detachment of receptor proteins

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Ameboid movement

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Ameboid movement

• Cells that exhibit ameboid motion– WBC– Fibroblasts– Embryonic cells

• Control of ameboid motion– Chemotaxis• Positive• Negative

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Cilia and Ciliary movements

• Whiplike movement of cilia on the surfaces of cells

• A sharp pointed hair projecting 2-4micrometers from the surface of the cell.

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Structure of a cilium

• Covered by an outcropping of cell membrane• Supported by 11 microtubules, 9 double

tubules at the periphery and 2 single tubules down the center.

• Each cilium is an outgrowth of a structure that lies immediately beneath the cell membrane, called basal body of the cilium

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• All the tubules are linked to one another by a complex of protein cross linkages, together called the axoneme.

• Multiple protein arms composed of the protein dynein (having ATPase activity) project outward from each double tubule

• ATP and appropriate magnesium and calcium concentration required.

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Mechanism of ciliary movement

• Sudden fast forward whip like stroke• Slow backward stroke• An effective way of pushing the fluid in the

direction of forward stroke.

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• CELLS EXHIBITING CILIARY MOVEMENT

• 1- Respiratory airways• 2- Uterine tubes of the female reproductive

tract.

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Q & A