endocytosis and vesicle trafficking

endocytosis

the process of uptake of outside material by invagination of the plasma membrane followed by pinching off and intracellular vesicle formation

function of phagocytosis

ingestion/removal of bacteria

mechanism of phagocytosis

activation of receptors that bind bacteria -> activation of F-actin polymerisation, plasma membrane protrudes and zippers around particle, phargosome is sealed off
f-actin disassembles, phagosome transported into cell, fuses with lysosome to form a phagoysosome

function of macropinocytosis

uptake of fluid for feeding and removal of large number of growth factor receptors from plasma membrane

function of clathrin-mediated endocytosis (CME)

receptor mediated endocytosis allows the cell to take up specific macromolecules which are not abundant in the extracellular fluid via more than 25 different receptors, dynamin-dependent (involves pinching of membrane)

two types of clathrin-mediated endocytosis

constitutive receptor mediated and ligand enduced receptor mediated

constitutive receptor mediated endocytosis

type of CME, used for iron uptake via transferrin and cholesterol uptake via LDL-receptor

ligand induced receptor mediated endocytosis

type of CME, used for modulation of growth factor signalling

what is the role of f-actin polymerisation in CME?

supports vesicle scission and transport of vesicle away from the plasma membran

caveolin-mediated endocytosis

caveolin self-associates to form a coat and together with cholesterol in the membrane to cause membrane invagination