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Cell Biology 

Lecture 223.20: Endocytosis and Exocytosis

Endocytosis

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Endocytosis-green arrows

Two Types (based on size)

 pinocytosis (cellular drinking) < 150 nm; all cell phagocytosis (cellular eating) > 250 nm; phagocytic cells

receptor mediated

Pathways to Lysosomes

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Phagocytosis

Phagocytosis

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Pathways to Lysosomes

Endocytosis

*

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Endocytosis: Receptor-mediated

Endocytosis: Receptor-mediated

• 

Selective process

• Mediated by clathrin 

and transmembrane

receptor on cell surface

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Endocytosis - sorting in the endosome

Examples

Recycling - LDL receptor

Degradation - EGF receptor

Transcytosis - antibodies

Endocytosis -Sorting

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Endocytosis - sorting in the endosome

Examples

Recycling - LDL receptor

Degradation - EGF receptor

Transcytosis - antibodies

Sorting in Trans-Golgi Network 

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Signal-mediated delivery to lysosomes

Lysosomal proteins are modified further in the Golgi

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Sorting in the Golgi- Lysosome Delivery

Sorting - Lysosome Delivery

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Exocytosis - Regulated Secretion

Exocytosis - Constitutive Secretion

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Exocytosis - Constitutive Secretion

Exocytosis - Regulated vs. Constitutive Secretion

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end