Endosomes And Lysosomes

Front 1

phagocytosis

Back 1

-cell eating; ingestion of bacteria, large particles or other cells
-occurs mainly in specialized cell types such as neutrophils and macrophages

Front 2

pinocytosis

Back 2

-cell drinking; ingestion of solutes such as proteins, hormones and macromolecular complexes in liquid medium
-occurs in all cell types

Front 3

clathrin dependent pinocytosis

Back 3

-receptor mediated endocytosis
-type of pinocytosis

Front 4

caveolae

Back 4

-ingestion of small vesicles formed by aggregation of caveolin in lipid rafts
-type of pinocytosis

Front 5

macropinocytosis

Back 5

-uptake of liquid in large vesicles formed by extensions of plasma membrane

Front 6

4 main steps of phagocytosis

Back 6

1. binding of material at extracellular surface of plasma membrane
2. extension of plasm membrane (pseudopodia) by microfilament-dependent movement
3. formation of large intracellular vesicles (phagosomes) by fusion of pseudopodia
4. fusion of phagosomes with lysosomes for enzymatic digestion (phagolysosomes)

Front 7

phagocytosis

Back 7

-cell eating; ingestion of bacteria, large particles or other cells
-occurs mainly in specialized cell types such as neutrophils and macrophages

Front 8

pinocytosis

Back 8

-cell drinking; ingestion of solutes such as proteins, hormones and macromolecular complexes in liquid medium
-occurs in all cell types

Front 9

clathrin dependent pinocytosis

Back 9

-receptor mediated endocytosis
-type of pinocytosis

Front 10

caveolae

Back 10

-ingestion of small vesicles formed by aggregation of caveolin in lipid rafts
-type of pinocytosis

Front 11

macropinocytosis

Back 11

-uptake of liquid in large vesicles formed by extensions of plasma membrane

Front 12

4 main steps of phagocytosis

Back 12

1. binding of material at extracellular surface of plasma membrane
2. extension of plasm membrane (pseudopodia) by microfilament-dependent movement
3. formation of large intracellular vesicles (phagosomes) by fusion of pseudopodia
4. fusion of phagosomes with lysosomes for enzymatic digestion (phagolysosomes)

Front 13

Dynamin

Back 13

GTPase in plasma membrane required for budding of clathrin coated vesicle from clathrin coated pits

Front 14

structure/function of clathrin

Back 14

-distorts plasma membrane by budding to produce vesicle
-captures membrane receptors and bound molecules

Y
heavy chain (arm) and light chain (internal) and binding site for assembly particles (hands)

Front 15

adapter proteins

Back 15

-on inner coat of clathrin
-consists of adaptin subunits
-provides specificity by coupling of receptor to clathrin coated pit

Front 16

what is recylced?

Back 16

clathrin coat reforms transport vesicle that takes adapter proteins and receptors (after fusion with early endosome) back to plasma membrane

Front 17

what occurs after internalization? -up to sorting

Back 17

clathrin coat dissociates and fusion between vesicle and early endosome
-ligand and receptor dissociate
-ligand (cargo protein)

Front 18

pH of lumen of early endosome how and what significance?

Back 18

6.0
H+ pump lowers to this pH
causes dissociation of ligand and receptor

Front 19

endocytic vesicles

Back 19

-buds from early endosome
-carries ligand to late endosomes

Front 20

pH of late endosomes and significance

Back 20

approx 5.5 then lowered to 5.0
-activates lysosomal hydrolases

Front 21

what occurs after sorting?

Back 21

-endocytic vesicles fuse with late endosome
-lysosomal hydrolases from trans Golgi network (tagged with mannose-6-p, so sorting occurs for those without tag) in vesicles are fused with late endosome
-late endosome lowers pH to 5.0, activating enzymes
-recycling of endosome membrane proteins back to trans Golgi

Front 22

how are vesicles transported?
-note from Bradshaw lecture

Back 22

transported along microtubules using either dyne in motor proteins (towards minus end of MT) or kinesins (towards plus end of MT)

Front 23

types of ligands (8)

Back 23

hormones
growth factors
lipoproteins
antibodies
vitamins
iron binding proteins
toxins
viruses

Front 24

significance of multivesicular body

Back 24

-ligand and receptor are degraded in lysosomes
-eg EGF (epidermal growth factor) receptor is tagged with ubiquitin
-integral membrane protein (receptor in this eg) is sorted in to small vesicles in late endosome
-accumulation of small vesicles gives rise to multivesicular body which fuses with lysosome and degrades membrane and associated proteins of the vesicles

Front 25

function of MVBs

Back 25

-sorting and degradation of integral membrane proteins
-hormone desensitization by down-regulatoin of receptor

Front 26

caveloae structure/location

Back 26

-invaginations of plasma membrane, 50-80 nm
-integral membrane proteins, NOT RECEPTOR MEDIATED
-abundant in vascular endothelial cells, smooth muscle cells, fibroblasts and adipocytes

Front 27

caveolins molecular components

Back 27

-integral membrane proteins
-type of lipid raft
-cholesterol and sphingolipids microdomains, stabilized by caveolin proteins

Front 28

caveolins functions

Back 28

-endocytosis- bud as vesicles from plasm memrane and fuse with either caveosomes or early endosomes
-transytosis- bud as vesicles from cell surface, traverse the cell and fuse with plasma membrane at another location on cell surface

Front 29

what protects lysosome from self digestion?

Back 29

glycosylation of membrane proteins protects luminal surface of lysosome

Front 30

what do lysosomal enzymes contain and how are they sorted?

Back 30

contain N-linked oligosaccharides that are phosporlated in cis Golgi Network to generate Mannose-6-P tag
-Mannose-6-P binds to its receptor which binds to adaptor protein 1 on clathrin coat

Front 31

autophagy

Back 31

self digestion of organelles and proteins by the cell

Front 32

autophages

Back 32

membrane bound vacuoles derived from ER, enclose organelles or cytoplasm

Front 33

phagolysosomes

Back 33

autophages fuse with lysosomes to form these which digest contents

Front 34

what causes lysosomal storage diseases?

Back 34

autosomal recessive disorder causes deficiency in lysosomal enzyme
-results in accumulation of undegraded substrates

Front 35

I-Cell Disease
-what are cellular defects?

Back 35

-defective processing of Mannose-6-P tag
-lysosomal enzymes not sorted by golgi in to clathrin coated vesicles bound for lysosomes
-deficiency of multiple enzymes causes substrates to accumulate in cells and form inclusion bodies

Front 36

Tay--Sachs Disease
-what is the defective enzyme and what are the cellular defects?

Back 36

alpha hexosaminidase A
-accumulation of gM2 gangliosides in brain
-causes increase in glial cells and abnormal growth of dendritic processes of neurons

Front 37

Gaucher's Disease
-what is the defective enzyme and what are the cellular defects?

Back 37

beta glucocerebrosidase
-accumulation of glucocerebroside in macrophages
-leads to enlarged spleen and liver