Intracellular Vesicular Traffic 2 Flashcards
What is a lysosome?
membrane enclosed compartments filled with hydrolytic enzymes
What do lysosomes require for optimal activation?
acidic environment and proteolytic cleavage
What does a lysosome do?
intracellular digestion of macromolecules
What does a vacuolar ATPase do?
pumps H+ into lysosomes to maintain the acidic pH and drive transport of small metabolites
What is the pH inside of lysosomes?
5
What does the pathway that transports from the golgi network to the lysosome do?
delivers membrane proteins and hydrolyses to lysosomes
Lysosomal hydrolyses have sorting signal _______ attached to them in the ______
mannose-6-phosphate, cis golgi network
What receptors in the trans golgi network recognize mannose?
mannose-6-phosphate receptors
What type of vesicles are lysosomal proteins packaged into that bud from the TGN?
clathrin coated
Where are lysosomal proteins delivered to?
endosomes then lysosomes
What causes lysosomal storage diseases?
genetic defects in lysosomal hydrolases resulting in accumulation of undigested material in lysosomes
What is Hurler’s disease?
mutation in enzyme required to break down glycosaminoglycan chains
What is inclusion cell disease?
all of the lysosomal hydrolyses are missing in many cell types. Undigested substrates accumulate as inclusions
__________ adds M6P to lysosomal hydrolases
GlcNAc phosphotransferase
What happens when GlcNAc phosphotransferse does not add M6P to lysosomal hydrolyses?
enyzymes are not phosphorylated and not sorted into vesicles and not delivered to lysosomes instead careered to cell surface and secreted
What is endocytosis?
uptake of macromolecules from exterior across plasma membrane
PM _______ and pinches off to form ______
invaginate; endocytic vesicles
What is phagocytosis?
large particles ingested by vesicles
What is pinocytosis
small particles ingested by vesicles
What is receptor mediated endocytosis used for?
import select macromolecules from outside cell
What is an example of receptor mediated endocytosis?
cholesterol uptake
What are the steps in receptor mediated endocytosis?
- molecule bind to receptors on membrane surface
- accumulate in clathrin coated pits
- enter cell as receptor macromolecular completely in clathrin coated vesicles
Receptor mediated endocytosis provides a ________ mechanism
selective concentration
Phagocytosis is carried out by _______
phagocytes
_______ fuse with lysosomes and ingested material is ______
phagosomes; degraded
How is undigested material secreted?
via exocytosis
Phagocytosis triggered by _______ to receptors on phagocyte surface
binding of particle
What is pseudopod formation driven by?
localized actin polymerization and reorganization
antibodies binding to microbe triggers formation of a _____ which engulfs the particle and forms a _____
pseudopod; phagosome
What is phagocytosis controlled by?
Rho GTPses and phosphoionositide signaling
Where does pinocytosis begin?
at clathrin coated pits
What are caveolae?
flask shaped invaginations in PM
Caveolae are enriched in ____ and ____ and ______
cholesterol; glycospingolipids; GPI anchored membrane proteins
What is the structural protein of a caveolae?
caveolin
Caveolae invaginate into membrane by virtue of ________ composition and not the protein coat
lipid
Do caveolae connect or not connect with lysosomes?
do not connect
Where does exocytosis transport vesicles?
trans golgi network to plasma membrane
How often do constitutive secretory pathways operate?
continously
When do regulated secretory pathways operate?
when triggered by signals
