: intracellular trafficking and polarity

Bulk transport

active vesicular transport]

Cell polarity

morphological and biochemical asymmetry

Endocytosis

internalization of molecules  invaginaiton of PM around target particle then fission.

Endomembrane system

group of membranes and organelles working together to modify, package and transport lipids and proteins (ER, Golgi apparatus, and lysosomes.)

Exocytosis

direction of secretory vesicles to the cell membrane  either secreted to the extracellular environment or added to the PM. STEPS: budding – tethering – docking – priming (neurons) – fusion (response to calcium elevation)

Phagocytosis

cellular eating for large solid particles (bacteria or cellular debris). Particle binds to receptor leads to actin cytoskeleton rearrangements which forms a phagosome which fuses with lysosome (phagolysosome)  digested

Phophoinositides (Pi)

lipids that control the correct timing and location of trafficking events

Pinocytosis

macropinocytosis: nutrients and fluids (cellular drinking) and micropinocytosis: small molecules and membrane receptors (highly specific)

Polarity protein complexes (PAR)

master regulator of polarity establishment in many cell types

Coat proteins

vesicle budding and cargo selection  physically reshape the membrane into a bud and attach the transport carrier to cytoskeleton (COPI)

RAB-GTPases

molecular switches: off when GDP bound, on when GTP bound. NO PHOSPHORYLATION  the guanine-nucleotide exchange factor (GEF) exchanges the GDP by a GTP to turn on, and its turned off by a GAP (liberation of a Pi)

Secretion

consitutive  continuous and not regulated stream of vesicles with lipids and proteins for extracellular matric or PM. Regulated  for proteins that are stored and secreted on demand

SNARE proteins

Vesicle targeting and fusion  V-snare (membranes of transport vesicles) and T-snare (target membrane)  form the SNARE complexe when bound

Transcytosis

type of endocytosis that transports internalized proteins to the opposite surface