Endocytosis Flashcards Preview

CTO Quiz 1 > Endocytosis > Flashcards

Flashcards in Endocytosis Deck (16):
1

"Pinocytosis"

Ingestion of small particles (<150nm)

2

Constitutive pinocytosis

Caveolin on lipid raft forms caveoli (conformational)
Dynamin (GTPase) separates from membrane
Depends on caveolin concentrations/cell specialization

3

Receptor mediated pinocytosis/endocytosis

Membrane receptor
Recruits adaptin (AP2), recruits clathrin -> conformational sphere
Dynamin (GTPase) separates
AP2 and clathrin recycled to cytosol
Rab5 targets and SNARE fuses vesicle to endosome

4

Clathrin

Triskelion molecule, forms spherical pit when associated

5

Pinocytosis vesicle specificity

Rab5 and SNARE present in raft with receptor
Rab5 - specificity of destination
SNARE - bilayer fusion
AP2 and clathrin non-specific, recycled after separation

6

Examples of receptor-mediated endocytosis

Protein hormones (insuliln, LH, FSH, GH, prolactin, glucagon)
Growth factors
Lymphokines
Nutrients (LDL, transferrin)

* Basically any protein or larger molecule that needs to enter cell!

7

Endosomal system

Tethering proteins/receptors specific to Rab
SNAREs (t) mate with vesicle SNARE (v)
Slight acidity prompts release of cargo from receptor
Receptors recycled to membrane in vesicles

8

Endosome vs lysosome

Slightly acidic
No hydrolase activity in early endosome
Endosome does not become lysosome

9

Endosome/lysosome pH

Early endosome - 6, no hydrolases
Late endosome - 5.5-6, hydrolases, H+ ATPase
Lysosome - <5, hydrolases, H+ ATPase

10

Endocytic pathway

Contents transported in multivesicular bodies (MVB)
Guided by ESCRT proteins
Late endosomes can fuse with lysosomes

11

Acid hydrolases

Only function at low pH (protective if lysosomal membrane failure)
Labelled with mannose-6-phos to target to late endosome or lysosome
Wide range for catabolism of various molecules

12

Appearance of lysosomes

Depends on cell activity
Can be large, usually homogenous vs MVB
Ex granules in WBC

13

Familial hypercholesterolemia

Dysfunction of LDL receptor - binds LDL but can't bind AP2 (not endocytosed)
Grossly elevated serum, early CAD, stenosis, xanthomas

14

Phagocytosis

Opsonization of bacteria by antibodies, complement
Receptors trigger actin->pseudopodia
Lysosomes fuse with phagosome to expose hydrolytic enzymes
Neutrophils and macrophages are "professionals"

15

Autophagy

Old/damaged organelles
ER encircles organelle, fuses with lysosome
Triple membrane vs phagosome (double)

16

Lipofuscin

Vesicles of lysosomal products that can't be broken down
Often visible in older cells
"residual bodies"