Lecture 15 - Endocytosis 1 Flashcards

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1
Q

What are the types of endocytosis?

A

Autophagy (cytosolic components are surrounded by plasma membrane)

Endocytosis

Phagocytosis

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2
Q

What is the function of phagocytosis? What happens to phagosomes after a phagocyte ingests harmful material?

A

Phagocytosis enable cells to eat large material. Phagosomes fuse with lysosomes where their content is digested.

Toxins are eliminated by this method and cells that are too old.

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3
Q

What mediates phagocytosis?

A

Cells that perform this use actin to do this. The actin pushes the membrane around the cell being phagocytosed.

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4
Q

How is an apoptotic cell eaten by a phagocyte?

A

Exposure of phosphatidyl serine site during apoptosis induces phagocyte to eat this apoptotic cell.

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5
Q

What is endocytosis?

A

Ingestion of fluid via small vesicles.

Endocytosis involves exposure of a small segment of plasma membrane which buds inwards to form an intracellular vesicle.

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6
Q

What is the function of endocytosis in combination with exocytosis?

A

Exocytosis and endocytosis are linked. They allow maintenance of plasma membrane homeostasis. (maintenance of lipid and protein content of the plasma membrane)

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7
Q

What are the components of the clathrin coat?

A

triskelian made up of:

3 Binding sites for assembly of particles

3 heavy chains

3 light chains at base of heavy chains

1 clathrin coat is comprised of 36 triskelions (12 pentagons and 6 exagons)

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8
Q

How does clathrin coat assemble?

A

adaptor proteins (AP2) form a coat around the vesicle and under the clathrin coat.

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9
Q

What is the major advantage of clathrin-mediated endocytosis?

A

Clathrin coated pits represent a specific and highly efficient pathway for uptake of macromolecules, nutrients, and signalling molecules.

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10
Q

What is the problem with clathrin mediated endocytosis?

A

This pathway is frequently hijacked by pathogens to gain entry into cells.

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11
Q

What is the destination of vesicles of the endocytic pathway?

A

Endocytic pathway ends at lysosome but many branch points can divert traffic prior to reaching lysosome in a complex pathway.

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12
Q

What are the type of ligands that enter via receptor mediated endocytosis?

A

Hormones/growth factors

Serum transport factors + antibodies (eg from placenta)

Viruses

Toxins

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13
Q

What are the steps of clathrin-mediated endocytosis?

A

1) cargo molecules can interact with receptor.
2) adaptor molecule attaches to the cargo receptor.
3) clathrin attaches to the adaptor protein forming a vesicle.
4) vesicle is separated from membrane via dynamin. This is a GTP dependent process.
5) vesicle coat is separated and naked vesicle results.

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