Endocytosis, Lysosomes, Endosomes

Front 1

phagocytosis

Back 1

cell eating

Front 2

Phagocytosis occurs mainly in which types of cells?

Back 2

mainly in specialized cells like neutrophils and macrophages

Front 3

Pinocytosis. in which cells types? ingests what?

Back 3

cell drinking=ingestion of solutes such as protein hormones, macromolecule complexes in liquid medium

is prevanlent in all cell types

Front 4

Receptor Mediated Endocytosis (RME) is the ____dependent _____of what?

Back 4

clathrin dependent ingestion fo receptor bound material in clathrin-coated pits

Front 5

Caveolae is __________ formed by _______ in______

Back 5

the ingestion of small vesicles formed by aggregation of Caeolin in lipid rafts

Front 6

Macropinocytosis

Back 6

uptake of liquid in large vesicles formed by extensions of the plasma

Front 7

name the 3 types of pintocytosis

Back 7

RME, Caeolae, Macropinocytosis

Front 8

Steps of RME

Back 8

1) Ligands internalized specifically
2) sorted into clathrin coated pits in membrane
3) budding of pits from Plasma membrance to make clathrin vesicles (requires GTPase=Dynamin to pinch off)

Front 9

Structure of Clathrin.

Back 9

chain-link fence/cage/lattice when aggregates.

Front 10

Function of Clathrin

Back 10

1) distorts plasma membrane by building to produce vesicle
2)capture membrane receptors/bound molecules

Front 11

In Endocytosis, binding of _____and _____creates _______change in opposite part of protein to allow what?

Back 11

receptor and ligand creates conformational change in the opposite part of the protein to allow Adaptor Proetin 2 to bind to the specific AA sequence in the cytoplasmic tail domain of the receptor/clathrin coat

Front 12

The ligand, receptor, (with trans membrane protein) and Adaptor protein connect to the_____ and get...?

Back 12

clathrin cage on the outside of the cell and get sucked into like a black hole

Front 13

First step of RME Trafficking: At the Early Endosome...

Back 13

clathrin coat dissociates/vesicles fuse with Early Endosome

Front 14

Second step of RME Trafficking: early endosome membrane contains _____ that lowers ____ and causes...?

Back 14

H+pump that lowers pH of the lumen to 6.0, causing dissocation of the ligand from the receptor and triggers recycling of receptors back to plasma membrane

Front 15

Sorting in the Early Endosomes creates 2 types of vesicles that bud from the early endosome. What are they?

Back 15

1) transport (recycling) vesicles that carry receptors and membrance back to the plasma membrance

2)endocytic vesicles that carry ligand further on to the late endosome

Front 16

Late Endosomes have pH of ___, fuse with ___ carrying_____ from trans Golgi tagged with ________

Back 16

5.5 and fuse with transport vesicles carrying the lysosomal hydrolases from trans Golgi tagged withe Mannose 6Phosphate

Front 17

Late Endosomes mature into Lysosomes by...?

Back 17

1) sorting hydrolytic enzymes with ligand

2) recycling of endosome membrane proteins back to trans Golgi

3) lower pH to 5.0 for enzyme activation

Front 18

Vesicles are transported along microtubules via...?

which protein goes + and which protein goes - ?

Back 18

Dynein motor proteins (towards minus ends of MY) or Kinesins (toward the plus ends of MT)

Front 19

Name some examples of Ligands. 9 categories

Back 19

1) Hormones: insulin, glucagon, LH, Growth, Prolactin, TSH, TH
2) Growth Factors: Epidermal Growth Factor/Nerve Growth Factor
3) Lipoproteins, LDL, VLDL, HDL
4) Antibodies, IgE, IgG via Fc receptors
5) Vitamins: A,D, B12
6) Iron Binding Proteins: Transferrin
7)Toxins: Diptheria, Cholera
8) Viruses: adenovirus, rous sarcoma

Front 20

In some cases, some growth factor receptors, want to downregulate endocytosis. What does this and how? what is this called?

Back 20

MultiVesicular Bodies (MVB)
sort and degrade integral membrane proteins and help hormone desensitization by removing the receptors from the surface of the cell


Ex.) EGF-tagged for degradation by Ubiquitin

Front 21

Describe function of Ubiquitin. What happens then?

Back 21

Ubiquitin tags receptors to be sorted into small vesicles.

These vesicles bud from the late endosomes, accumulate in MVB, fuse with the lysosome, and are then degraded. Then hormone has less receptors to bind to on cell surface =desensitized

Front 22

Caveolae are a mechanism of what?

Where are they abundant?

Back 22

Mechanism of pinocytosis. ARE NOT RECEPTOR MEDIATED!

Abundant in vascular endothlial cells. Smooth muscles cells, fibroblasts and adipocytes.

Front 23

Caveolins are what? Where are they located and what do they help make up?

Back 23

Integral membrane proteins anchored into the plasma membrane in rigid lipid rafts, that help to make up caveolae.

Front 24

Function of Caveolae:

Back 24

1Endocytosis: byd as vesicles from plasma membrane/fuse with “caveosomes/early endosomes.

2) Transcytosis: bud as vesicles from cell surface, traverse the cell and fuse with plasma membrane at another location on cell surface

Front 25

Lysosomes. Describe size, electron density, internal components?

Back 25

variable in terms of size. Electron dense but not uniform. Lumen has many different types of Lysomal enzymes/acidic hydrolases.

Front 26

Lysosomes have a ____ which is used for activating....?

Back 26

proton pump (via ATP) lower pH to 5 for enzyme activation=fully active.

Front 27

Glycosylation of membrane proteins in lysosomes serve as _______ to protect membrane against....?

Back 27

glycoprotein lining to protect against it's own enzymes along the inner/luminal membrane

Front 28

Lysosomes have membrane transporters for...?

Back 28

release of digestion products (AA, sugars, lipids). You have to poop it out!

Front 29

Formation of Lysosomes: Tag for lysosomal enzymes? binding through ____. Fuses with ______. Low ____ dissociates _____. What is recycled to trans golgi? How do lysosomes become mature? pH?
Draw it out!

Back 29

1)Lysosomal enzyme tagged with Mannose 6-P in cis golgi
2)sort through golgi-trans golgi
3) M6Ps are not transmembrane, so have receptors that bind thru membrane to adaptor protein, then clathrin binds
4) clathrin coat sheds and then vesicle Fuses with late endosomes
5) Low pH (5.5) of Late Endosome dissociate M6P recepetors from enzymes
6)M6P receptors recycles back to trans golgi via transport vesicles
7)Late Endosomes mature into Lysosomes by sorting hydrolytic enzymes/lowering pH to 5.0 for enzyme activation

Front 30

Lysomal Storage Diseases

If problem with lysomal enzymes-going to have problem...

Back 30

digesting material that cells take up=diseases, especially in Tay Sachs

Front 31

Tay Sachs=

Back 31

a-Hexosamindidase A =accumulation of GM2 Gangliosides in brain-causes increase in Glial cells and abnormal growth of dendritic processes of neurons.

Mutation can’t break down gangliosides properly = accumulates+disrupts neural system

Front 32

Gaucher’s Disease=

Back 32

b-glucocerebrosidase accumulates in macrophages =heptamegaly/enlarged spleen

Front 33

I-Cell Disease=

Back 33

processing of mannose 6-p tag is defective. Cant sort lysosomal enzymes. Non specific. Lysosomes can’t degrade anything!