Receptor Mediated Endocytosis (6) Flashcards Preview

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Flashcards in Receptor Mediated Endocytosis (6) Deck (13)
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0

What is meant by vascular transport?

- Membrane vesicles bud from donor organelle and are transported to destination where they fuse with recipient organelle

1

What are the three main membrane internalisation methods?

- Phagocytosis: internalisation of particulate matter
- Pinocytosis: invagination of plasma membrane to form a vesicle
permits uptake of extracellular salutes
- Endocytosis: selective internalisation of molecules into cell by binding to specific cell surface receptors

2

What does REM stand for and give an example?

- Receptor mediated endocytosis
- Uptake of cholesterol

3

How do clathrin vesicles form and how are they disassembled?

- Clathrin coated pits form spontaneously and bud off to form vesicles
- Clathrin coated vesicles are uncoated by an ATP dependent uncoating protein
- Clathrin triskelions are recycled back to for new clathrin coated pits

4

What are the mutations affecting LDL receptors in hypercholesterolaemia?

- Normally binding receptor: no binding of LDL but still normal coated pits and internalisation
- Non functioning receptor: no internalisation, LDL receptors found distributed over whole cell surface, deletion of C-terminal cytoplasmic domain prevents interaction with clathrin coat.

10

Outline the receptor mediated endocytosis of LDLs and where do they end up?

- LDL moves into coated pit randomly
- Coated pit buds off to form coated vesicle (clathin cage formation)
- Uncoating of vesicle by ATP dependent uncoating protein
- Enters endosome
- Either moves to Golgi or lysosome

11

How does CURL happen in the endoscope?

- Compartment of uncoupling of receptor and ligand
- pH change due to high H+ concentration in endosome uncouples the receptor and ligand

12

After the LDL is processed in the endosome what are the possible options next?

- Ligand degraded
- Receptor recycled

13

How does ligand recycling occur?
- use transferrin as an example

- Apotransferrin taken in
- Ferrin is unloaded into endosome
- Apotransferrin remains bound in endosome so is released when endosome is recycled and exocytosed
- pH decrease doesn't cause decrease in affinity

14

How does transcytosis occur?

- From endosome to transfer vesicle
- NOT discharged in CURL
- Transfer vesicle has antibodies bound
- Moved to the bile where all contents are degraded
- Ligand and receptor are degraded.

15

Outline the process by which membrane enveloped viruses are endocytosed.

- Binds to cells by fortuitous association with cell receptors
- Entering cells via clathrin-coated pits (RME)
- Unfolding of hydrophobic domains in membrane, fusion proteins in response to acidic pH of endosome
- Inserting membrane fusion proteins into the endosome membrane leading to membrane fusion and release genomic RNA into cell cytoplasm
- Using host cell machinery to replicate RNA and capsid proteins -> new viruses at cell membrane.

16

Give two examples of toxins entering by receptor mediated endocytes

- Cholera
- Diptheria

17

Give three examples of coat proteins.

- Clathrin - plasma membrane coated pits
- COPI - ER
- COPII - Golgi