BI203 Lecture 17: Protein Sorting and Transport - Slides 88-104 (Vesicle Fusion, Endosomes, and Lysosomes)

Question 1

Two steps when a vesicle arrives at its destination:

Answer 1

docking, fusion

Question 2

Vesicle docking is controlled by the ___ family of proteins.

Answer 2

Rab

Question 3

Specific Rabs associate with specific transport vesicles & target membranes.

Rabs recruit ___ ___ ___ (MTFs).

Protein-protein interactions between ___ ___ ___ (MTFs) mediate vesicle docking at target membranes.

Answer 3

membrane tethering factors (MTFs)

Question 4

Fusion of a transport vesicle with its target:

1. The vesicle must recognize the correct ___ membrane.
2. Vesicle and target membrane must ___, delivering the contents to the target organelle.

Answer 4

target, fuse

Question 5

Interaction between transport vesicles and target membranes is mediated by ___ ___ ___ (MTFs) and small-GTP binding proteins (___ proteins).

Answer 5

membrane tethering factors (MTFs), Rab

Question 6

Vesicle Rab proteins in the active ___ state bind membrane tethering factors.

Answer 6

GTP-bound

Question 7

Tethering factors also bind coat proteins, and may stimulate formation of complexes between transmembrane proteins called ___.

Answer 7

SNAREs

Question 8

Formation of complexes between vesicle and target SNAREs is required for ___.

Answer 8

fusion

Question 9

___ pairing provides the energy to bring the two bilayers close enough to destabilize them and fuse.

Answer 9

SNARE-SNARE

Question 10

SNARE proteins have a central coiled-coil domain.

This domain binds to other coiled-coil domains and zips the SNAREs on ___ and ___ membranes together.

This brings the 2 membranes into direct contact and leads to ___ of the lipid bilayers.

Answer 10

vesicle, target, fusion

Question 11

Vesicle ___ and Target ___ interact with each other to form “coiled-coils”.

The coiling of the ___ around each other drives the membranes against each other.

Answer 11

v-SNAREs, t-SNAREs, SNAREs

Question 12

Lysosomal function is dependent on an internal pH of ___.

Lysosomal ___ ___ help maintain this acidic pH.

Answer 12

5, proton pumps

Question 13

Lysosomes need a pH of 5 because ___ ___ are only active at a pH of 5.

Answer 13

acid hydrolases

Question 14

___ - Membrane-enclosed organelles that contain enzymes to break down all types of biological polymers.

They are the digestive system of the cell.

They can vary in size and shape depending on the materials that have been taken up for digestion.

Answer 14

lysosomes

Question 15

Acid hydrolases are active inside the lysosome, but NOT in the ___. This is to prevent uncontrolled digestion of cell contents if the lysosome membrane breaks down.

Answer 15

cytoplasm

Question 16

Mutations in genes that encode lysosomal degradative enzymes result in ___ ___ ___ - undegraded material accumulates in the lysosomes of affected individuals.

Answer 16

lysosomal storage diseases

Question 17

___ ___ is caused by deficiency of glucocerebrosidase, which catalyzes hydrolysis of glucosylceramide to glucose and ceramide.

Answer 17

Gaucher disease

Question 18

Gaucher disease is caused by deficiency of ___, which catalyzes hydrolysis of glucosylceramide to glucose and ceramide.

Answer 18

glucocerebrosidase

Question 19

Gaucher disease is caused by deficiency of glucocerebrosidase, which catalyzes hydrolysis of glucosylceramide to ___ and ___.

Answer 19

glucose, ceramide

Question 20

In the most common form of Gaucher disease, ___ are the only cells affected. Their function is to eliminate aged and damaged cells by phagocytosis

Answer 20

macrophages

Question 21

Lysosomes digest material taken up from outside the cell by ___.

Answer 21

endocytosis

Question 22

Lysosomes are formed when transport vesicles from the ___ ___ fuse with a late endosome.

Answer 22

Trans-Golgi Network

Question 23

___ represent an intersection between the secretory pathway and the endocytic pathway.

Answer 23

Endosomes

Question 24

___ types of endosomes.

Answer 24

3

Question 25

Three types of endosomes:

Answer 25

early endosomes, recycling endosomes, late endosomes

Question 26

___ ___ fuse with endocytic vesicles from the plasma membrane.
They separate molecules for recycling from molecules destined for degradation in lysosomes.

Answer 26

early endosomes

Question 27

Molecules to be recycled are passed to ___ ___ and back to the plasma membrane.

Answer 27

recycling endosomes

Question 28

Lysosomes degrade:

1) Cellular materials (proteins, organelles) by ___.
2) Extracellular materials taken up by ___.

Answer 28

autophagy, phagocytosis

Question 29

___ - Turnover of the cell’s own components.

Important in embryonic development and programmed cell death.

Answer 29

autophagy

Question 30

Autophagy:

A small area of cytoplasm or organelle is enclosed in a vesicle (___) which fuses with a lysosome, and its contents are digested.

Answer 30

autophagosome