Zaidi Vesicular Traffic 2

Question 1

Lysosome contains about 40 different ____ enzymes.

For optimal activation, lysosomes require ___ ___ and an ___ environment.

This protein, ___ ___, pumps H+ into the lysosome to maintain the acidic pH inside.

The approximate acidity of a lysosome inside is near a pH of ___.

Answer 1

hydrolytic.

proteolytic cleavage. acidic.

Vacuolar ATPase.

5.

Question 2

Lysosomes go through these three stages before becoming a lysosome

Answer 2

early endosome –> late endosome –> endolysosome –> lysosome.

Question 3

These three pathways deliver materials to lysosomes:

Answer 3

1. Phagocytosis
2. Endocytosis
3. Autophagy

Question 4

During autophagy, the cytosol and organelles get engulfed into this structure, a(n) ___, which fuses with the ___ to make a ___.

Answer 4

autophagosome.

lysosome.

autophagolysosome.

Question 5

Transport from TGN (trans golgi network) to lysosomes delivers ___ ___ and ___ to lysosomes.

The transported proteins to the TGN initially come from the ___, transported via the ___ ___.

TGN buds off into ___ and develops into ___.

Answer 5

membrane proteins. hydrolases.

Rough ER. Golgi complex.

endosomes. lysosomes.

Question 6

This sorting signal ___ is located on the ___ ___, and they become attached to them in the ___.

M6P is recognized by ___ ___, which are located in the ___ ___ ___.

M6P receptors are packaged into ___-___ ___ that bud from the TGN.

Contents delivered into ___ and then to ___.

Answer 6

mannose-6-phosphate (M6P). lysosomal hydrolases. cis golgi network (CGN).

M6P receptors. trans golgi network (TGN).

clathrin-coated vesicles.

endosomes. lysosomes.

Question 7

This enzyme, ___ ___, adds M6P to the lysosomal hydrolases. Without it the enzymes are not phosphorylated and not sorted into vesicles or delivered into lysosomes.

Answer 7

GlcNAc phosphotransferase.

Question 8

Name two genetic defects in lysosomal hydrolases and describe them.

Both lead to accumulation of ___ ___ in lysosomes.

Answer 8

Hurler’s Disease (mutation in the enzyme required to break down glycosaminoglycan chains) and Inclusion Cell Disease (defective/missing GlcNAc phosphotransferase).

undigested material.

Question 9

What is endocytosis? The plasma membrane does this to form the endocytic vesicle.

Large particle ingestion is referred to as ___. Small particle ingestion is referred to as ___.

Answer 9

Uptake of macromolecules from exterior.

PM invaginates and then pinches off to form the endocytic vesicle.

phagocytosis (ingested by phagosomes). pinocytosis.

Question 10

T/F: The fusion of vesicles coming from the TGN is called endocytosis?

Answer 10

False. endocytosis only refers to uptake from the exterior of the cell’s plasma membrane.

Question 11

What is a common example of receptor-mediated endocytosis?

Describe receptor-mediated endocytosis.

Receptor-mediated endocytosis provides a selective ___ mechanism.

Blockage of this pathway results in ___.

Answer 11

cholesterol uptake.

Used to import select macromolecules from the outside. Molecules bind to receptors on membrane surface, accumulating in clathrin-coated pits.

concentration.

Atherosclerosis.

Question 12

Steps of cholesterol uptake:

Answer 12

1. Endocytosis
2. Uncoating (of clathrin)
3. Fusion with Endosome
4. Budding off of transport vesicles.
5. Return of LDL receptors to plasma membrane.

Question 13

The return of LDL receptors to the plasma membrane happens when vesicles bud off of this stage of endosome.

Answer 13

Early.

Question 14

A defective ___ ___ ___, normally located in the clathrin coated pits, prevents ___ uptake by the cell. This leads to high levels of ___ in the blood, increasing the chance of forming atherosclerotic plaques.

Answer 14

LDL receptor protein.

LDL.

cholesterol.

Question 15

This kind of tag helps to sequester endocytosed proteins.

What are three possible fates of endocytosed receptor proteins?

Answer 15

ubiquitin.

1. degradation in endolysosome.
2. transcytosis of transport vesicle.
3. recycling of transport vesicles.

Question 16

Binding of ___ acts like an intracellular signal, causing relocalization of glucose receptors from ___ ___ to the plasma membrane in order to increase glucose uptake.

Answer 16

recycling endosomes. insulin.

Question 17

These two WBCs are phagocytes.

Phagosomes fuse with ___ and ingested material is degraded.

___ material is secreted out by exocytosis.

Answer 17

macrophages and neutrophils.

lysosomes.

Undigested.

Question 18

phagocytosis is triggered by binding of particle to receptors on phagocyte surface. Binding triggers formation of ___ which engulfs the particle and forms ___.

Formation of pseudopod driven by localized ___ ___ and ___, and controlled by ___ ___ and ___ ___.

Answer 18

pseudopod.

phagosome.

actin polymerization. reorganization.

Rho GTPases. phosphoinositide signaling.

Question 19

This enzyme, ___, converts PIP2 to ___. This conversion causes the bacteria to get phagocytosed by WBCs.

Answer 19

PI 3-kinase.

PIP3.

Question 20

This process, where the cell ingests bits of PM, occurs continuously in all eukaryotic cells. The process begins at ___-___ ___. Invagination includes both the extracellular fluid and various solutes.

Answer 20

Pinocytosis.

clathrin-coated pits.

Question 21

Flash-shaped invaginations in the PM are known as ___, which are enriched in ___ and ___, and GPI-anchored.

The major structural protein of caveolae is ___. Caveolae invaginate into membrane by virtue of ___ ___.

Answer 21

Caveolae. cholesterol. glycosphingolipids.

caveolin.

lipid composition.

Question 22

T/F: Pinched off caveolae connect with lysosomes.

Answer 22

False. Caveolae do NOT connect with lysosomes.

Question 23

Exocytosis involves transport of vesicles from and to what cellular compartments?

Secretory pathways triggered by signals are called ___, and pathways operating continuously are called ___.

Answer 23

Exocytosis: From TGN to PM. Fusion of vesicles with PM is called exocytosis.

Regulated. Constitutive.

Question 24

Proteins destined for secretion are packed into secretory vesicles in the ___. The protein packing occurs via ___ ___.

TGN also promotes ___ ___ of the secretory proteins.

Proteins going back to the TGN are concentrated in clathrin-coated ___ vesicles.

Answer 24

TGN.

selective aggregation/clumping.

proteolytic processing.

retrieval.

Question 25

Name the two types of t-snares.

v-snares, aka ___, is located on the lumen of the synaptic vesicle.

Name the 5 steps of synaptic vesicle exocytosis.

Answer 25

SNAP25 and syntaxin are the two types of t-snares.

synaptobrevin.

1. Docking
2. Priming I
3. Priming II
4. Fusion Pore Opening
5. Fusion Complete

Question 26

Calcium binds to this protein on the synaptic vesicle, ___. This functions to remove the ___ block of the SNARE bundle.

This allows the fused pore to do what?

Answer 26

synaptotagmin.

complexin.

Removing the complexin block allows fusion pore binding and opening.