5,2 Flashcards
Macromolecules in the form of——-&——- require a bulk transport system for transportation
Polysacharides and proteins
Types of endocytosis
1 phagocytosis
By the immune cells (macro phages)
They extend cytoplasmic projections pseudopods and they wrap around cellular debris and even entire cells forming a phagosome
2 pinocytosis : it doesnt involve receptors its like drinking of the cell cells take extracellular fluid with dissolved solutes
3 Receptor mediated endocytosis
Specific molecules bind to receptors
Lung
Lymph nodes
Tissues
Kidneys
Alveolar macrophages
Follicular dendritic cells
Histocytes
Mesangial cells
Phagocytosis
In response of binding a particle to receptors the cells extend pseudopods to wrap around the particles increasing surface for binding and then membrane invagination and zippering mechanism forming phagosome they bind to lysosomes formin phagolysosomes
receptor-mediated endocytosis
• •
uptake of cholesterol
uptake of ferric (Fe3+) ions by transferrin uptake of occupied insulin receptors
receptor-mediated endocytosis
• •
uptake of cholesterol
uptake of ferric (Fe3+) ions by transferrin uptake of occupied insulin receptors
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Coat is formed from
Very small 3 legged structure triskelion
Comprised from 3heavy chains 190kDa
And each bearing a light chain 25kDa forming a basketball like structure 8 hexagons and 12 pentagons
The coat formation is ——-while the degridation requires an ——
Energy independent
ATP dependent uncoating protein
Clathrin coat is atached to plasma membrane by
A number of integral proteoin that are called adapter they association with both clatherin and receptors
Naturally occuring mutations to LDL receptor have been identified in
Mutations include
Hypercholestrolemia
Receptor deficiency mutations prevent receptor expression
Nonfunctioning they cant bind to LDL Normal coated pits and internalisation.
- Receptor binding normal: no internalisation due to a deletion in the C terminal of
the receptor that makes the interaction with the coated pits. LDL receptors are found distributed over the whole cell surface in these patients.
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