Endomembrane System Part 2 - Lysosome Flashcards
what is the lysosome comparable to
the vacuole in plants
what is the lysosome
a digestive organelle that degrades all types of macromolecules
what is autophagy
degradation of larger cellular components/organelles
what does the lysosome play a key role in
autophagy
what does the lysosome contain
~60 different soluble acid hydrolase enzymes
when are soluble acid hydrolase enzymes active
only at low pH (about 4.6) of lysosome interior
how are resident lysosomal membrane proteins protected from degradation by acid hydrolase
lumen-facing carbohydrate groups
what happens to products of degradation
they are transported to cytoplasm to be reused by various biosynthetic/metabolic pathways
how is the low pH in lysosomal lumen maintained
membrane-bound ATPase proton pumps
what is the biosynthetic pathway
trafficking proteins to lysosomes
gist of biosynthetic pathway
lysosomal proteins synthesized and initially N-glycosylated in RER, then transported from ERES to golgi where they get further modified in cis-cisternae
what is M6P
signal patch - lysosomal targeting signal
fate of proteins without M6P
TGN–> secretory vesicles/granules–>pm/ECM
fate of proteins with M6P
TGN–>clathrin coated vesicle–>late endosome–>lysosome
what are late endosomes responsible for
uptake of plasma membrane proteins/receptors and extracellular materials/ligands
delivery to endosomes/lysosomes for internalization and/or degradation
what is the M6P receptor
integral transmembrane protein who’s luminal-facing domain binds to M6P groups on proteins
what are AP1 and GGA adapter coat proteins
cytoplasmic proteins with multiple protein-protein binding domains
what is Arf1 comparable to
Sar1 in COPII at ERES
what is Arf1 involved with
initiation of COPI-vesicle assembly during retrograde transport from and within Golgi complex
what does the binding of Arf1 to GTP cause
conformational change
how does Arf1 undergo conformational change
exposed lipid anchor in Arf1-GTP directs it from cytoplasm to outer leaflet of TGN membrane
what does one molecule of clathrin consist of
3 light chain polypeptides
3 heavy chain polypeptides
what structure does clathrin form
3 legged: triskelion
what do clathrin triskelions recruited from cytoplasm do
self assemble to form outer scaffolding of coat on growing vesicle
