411 Flashcards
Bulk phase endocytosis aka pinocytosis
nonspecific uptake of extracellular fluids
Receptor mediated endocytosis aka clathrin mediated endocytosis
Uptake of specific molecules (ligands) following binding to receptors
What happens to . Substances that enter a cell by means of clathrin-mediated RME
They bind to groups of receptors called coated pits, which invaginate into the cytoplasm, then pinch and come into the cell
Adaptors can form in clathrin mediated endocytosis. What do these do?
AP2 subunit engages cytoplasmic tails of recptors, leading to concentration of receptors in vesicle
COPI and clathrin coats
Outer geometric scaffold, inner adaptors. Overlapping subunits
COPII lattice
no overlapping subunits
Dynamin
GTP binding/accessory protein that is required for fission of vesicle from membrane where it forms by making a collar and choking it off
Housekeeping receptors
Take up stuff that is used by the cell (Eg transferrin and LDL)
Signalling receptors
Bind extracellular ligands, carry messages to do activities (hormones, insulin, etc)
Endocytosis for housekeeping receptors
delivery of bound materials to cell
Endocytosis of signalling receptors
Receptor downregulation- destruction of receptors
How does destruction of signalling receptors work?
Attaching ubiquitin tag
Endosomes
Distribution centers along endocytic pathway (Early if near peripheral region of cell- also sort stuff), late if close to nucleus)
How do molecules get from receptors to early endosomes
Vesicles
How do LDL receptors work?
Taken to plasma membranes in cells, concentrated in coated pits, bind to LDLs, make vesicles, disassemble clathrin coat, receptors returned to membrane. LDLs delivered to endosomes, proteins are degraded/processed and used by cell
Phagocytosis
Membrane folds in around cell, either forms phagosome with it contained in a vesicle or phagolysosome if connected with transport vesicle with lysosomal enzymes connected too
