Exam 3: Ch 14 Receptor-Mediated Endocytosis

Question 1

phagocytosis

Answer 1

nonselective process where extensions of the plasma membrane enveloped ingested material, forming phagosomes

Question 2

receptor-mediated endocytosis

Answer 2

receptor on cell surface binds to extracellular ligand

plasma membrane region with receptor-ligand complex buds inward and pinches off, making a transport vesicle

ex. LDL, transferrin, insulin, glycoproteins

Question 3

receptor mediated endocytosis uses what vesicles

Answer 3

clathrin/AP2

Question 4

can accidentally secreted lysosomal enzymes move back into the cell by receptor mediated endocytosis?

Answer 4

yes, there are M6P receptors on the cell surface

Question 5

what happens to the transmembrane receptors proteins that uptake extracellular ligand

Answer 5

internalized during endocytosis then sorted and recycled back to the cell surface

Question 6

gonads want cholesterol

Answer 6

send to smooth ER

Question 7

lipoprotein

Answer 7

lipid protein complex

shell made of apolipoproteins

cholesterol containing phospholipid monolayer

Question 8

LDL experiment to show how it enters cells

Answer 8

radiolabeled I^125 pulse-chase

electron dense label to LDL

Question 9

order of LDL uptake

Answer 9

surface binding of LDL

internalization

degradation

Question 10

what happens to LDL in lysosomes

Answer 10

apolipoproteins hydrolyzed

cholesterol esterases hydrolyze cholesterol esters

unesterified cholesterol leaves to be used in the cell

Question 11

what about the late endosome causes receptor-ligand complexes to dissociate

Answer 11

acidic pH

receptors recycled back to membrane by exocytosis

Question 12

the endocytic pathway delivers iron to cells without dissociation of the…

Answer 12

receptor-transferrin complex in late endosomes

Question 13

major function of lysosome

Answer 13

degrade extracellular materials and intracellular components

Question 14

pathway to degrade endocytosed membrane proteins in lysosome

Answer 14

uses an unusual vesicle that buds into the lumen of the endosome to produce a multivesicular endosome

eventual fusion with lysosome

Question 15

autophagy

Answer 15

formation of a double membrane organelle known as an autophagosome that enveloped cytosolic material

occurs when cells are placed under stress so macromolecules are used for nutrients

eventual fusion with lysosome

Question 16

what do multivesicular endosomes segregate

Answer 16

membrane proteins destined for lysosomal membrane

proteins destined for lysosomal degradation

Question 17

multivesicular endosomes

Answer 17

endosomes containing many vesicles in their lumen formed from vesicles budding inward

fuses with lysosome to deliver internal vesicles for degradation

Question 18

most cargo proteins entering multivesicular endosomes are tagged with

Answer 18

ubiquitin

Question 19

retroviruses bud from the plasma membrane in a process similar to formation of…

Answer 19

multivesicular endosomes

HIV uses gag protein that attracts ESCRT protein

Question 20

where does the autophagic vesicle come from

Answer 20

experiments show maybe gogi

in starvation… random

Question 21

how do autophagic vesicles grow

Answer 21

fusion with transport vesicles

Question 22

how do autophagic vesicles target the lysosome and fuse

Answer 22

outer membrane has proteins that target lysosome