Lecture 11

Question 1

what do lysosomal enzymes utilize to be sorted and transported at the Trans Golgi Network (TGN) ?

Answer 1

Clathrin-coated vesicles

Question 2

Where and what are lysosomal proteins tagged with? What occurs when tagged?

Answer 2

Tagged in the Cis-Golgi with phosphorylated mannose

once tagged, they’re recognized / captured by mannose 6-phosphate receptors

Question 3

what initiate membrane curvature and recruits adaptors?

Answer 3

G-Protein attached to the clathrin coated vesicles

Question 4

from where do packed secretory granules arise from? When are they released?

Answer 4

When secreted proteins released by regulated secretion form selective aggregates which become secretory granules

They’re released after stimulation by a hormone or nerve impulse

Question 5

What are the steps that occur between vesicle budding and vesicle fusion?

Answer 5

1. movement of vesicle towards target compartment (by microtubules & motor proteins)
2. Tethering of vesicles to target compartment (by tethering proteins)
3. docking vesicles to target compartment (by interaction of integral proteins)
4. Fusion of vesicle and target membrane

Question 6

What are Rabs and how do they cycle?

Answer 6

Family of small G proteins

cycle between active GTP and inactive GDP states

Question 7

True of False?
Rabs are associated with one type of membrane compartment.

Answer 7

False, they are associated with many different membrane compartments

Question 8

What are SNAREs and their function? what are the 2 types and where are they located?

Answer 8

Family of proteins localized to specific compartments

They bring vesicles and target compartments within close contact

v-Snare is found in transport vesicles

t-Snares are found in target compartments

Question 9

How many T and V snares are located in nerve cells and where can they be found?

How do they interact with each other?

Answer 9

2 t-snares on the plasma membrane

1 v-snare on the synaptic vesicle

Interact to form 4 strand bundles which pulls the lipid bilayers very close together

Question 10

What is exocytosis and what triggers it?

Answer 10

Discharge of secretory vesicle / granule

triggered by Ca2+ increases

Question 11

how do fusion pores form?

Answer 11

when vesicle and plasma membranes form together

Question 12

True or false?
Extracellular vesicles can move through the body unnoticed by the immune system?

Answer 12

True. They can!

Question 13

True or False?
The hydrolytic enzymes in lysosomes can hydrolyze nearly every macromolecule in the body?

Answer 13

True

Question 14

Where do Lysosomal enzymes have optimal activity for acid hydrolases?

Answer 14

In the Acidic Lumen

Question 15

Single-cell organisms and phagocytic White Blood Cells can digest materials by fusing what together?

Answer 15

by fusing phagosomes and lysosomes

Question 16

What is involved in the process of autophagy?

Answer 16

When lysosomes regulate organelle turnover

Question 17

How are autolysosomes formed to degrade organelles?

Answer 17

a phagophore envelops an organelle.

This double membraned vesicle created is called an autophagosome

The autophagosome fuses with a lysosome which creates an autolysosome which can now degrade the enclosed materials

Question 18

What is the benefit to Autophagy?

Answer 18

intracellular protection (abnormal proteins / bacteria)
Cancer prevention

Question 19

What are the 2 mechanisms to move materials into cells? what is the difference?

Answer 19

Endocytosis - cell - surface receptors and bound extracellular ligands

Phagocytosis - uptake particulate matter

Question 20

What are the 2 categories of Endocytosis and what do they uptake?

Answer 20

Bulk phases endocytosis: non-specific uptake of ECF

Receptor mediated endocytosis: uptake of specific macromolecules that bind to receptors on membrane

Question 21

What mediates Receptor mediated endocytosis? What does it result in?

Answer 21

Clathrin. results in coated pits that can pinch off the membrane into the cytoplasm

Question 22

What does each Clathrin molecule contain? What assembly does it form?

Answer 22

3 heavy chains and 3 light chains. forms a triskelion

Question 23

what do coated vesicles contain two dozen of and what does it form? what are some of the roles?

Answer 23

2 dozen proteins that form a dynamic network of interacting molecules

Have roles in cargo recruitment, coat assembly and membrane bending

Question 24

What is Dynamin and what is it required for?

Answer 24

G protein required for fission of the vesicle from the membrane

Question 25

what are endosomes?

Answer 25

Vesicle bound materials transported in vesicles and tubules

Question 26

Where are early endosomes located?

Answer 26

Near the edge of the cell membrane

Question 27

What are low-density lipoproteins made of? what are they for

Answer 27

Complex of cholesterol and proteins

taken up by receptor mediated endocytosis at the membrane for use by the cell

Question 28

What is the purpose of phagocytosis?

Answer 28

uptake of relatively large particles

Question 29

What is a phagosome and phagolysosome?

Answer 29

1. the vacuole pinched off the membrane
2. the product of the phagosome (vacuole) and lysosome fusing together

Question 30

What are Peroxisomes, what do they contain and involved in?

Answer 30

small membrane enclosed organelles
contain enzymes
involved in metabolic reactions for metabolism

Question 31

What are the 2 sub compartments of peroxisomes where an imported protein can be placed?

Answer 31

the boundary membrane and internal matrix

Question 32

What 2 complexes do mitochondria use for importing proteins?

Answer 32

the TOM complex for outer membrane
the TIM complex for inner membrane

Question 33

▪ Distinguish the functions of the different types of vesicle transport.
▪ Explain the functions of lysosomes.
▪ Explain the processes involved in the bulk transport of materials
into the cell.
▪ Describe how proteins are taken up by mitochondria, chloroplasts,
and peroxisomes.