Lecture 1: Membrane Trafficking

Question 1

What is cell polarization? Why is important for cell development

Answer 1

Cells are polar meaning they have different functions at different ends.

polarized cells define the inside and outside as well as transmit signals from one end to another

Question 2

What causes cell polarization?

Answer 2

membrane trafficking

Question 3

Define Membrane trafficking.

What are the two different types of membrane trafficking?

Answer 3

membrane trafficking is basically sending different proteins to different domains

1. Exocytosis directly to the target domain
2. Exocytosis of everything to the same domain followed by certain substances being endocytosed and recycled to the target domain

Question 4

Outline the key concepts in the secretory pathway

Answer 4

1. some trafficking routes are polarized- meaning that there are different beginning and end routes
2. proteins are organized at sorting stations
3. different routes are balanced by retrieval pathways

Question 5

what is the default pathway

Answer 5

most cargo moves through constitutive secretion- where they just move through the ER to golgi complex to arrive at the plasma membrane

Question 6

How can secretion release concentrated cargo

Answer 6

clathrin-coated vesicles can return membrane back to the golgi and as it does so will shrink the vesicle and make the cargo more concentrated

Question 7

Regulated Secretion

Answer 7

this is when vesicles are fully formed but must wait for a signal in order to fuse to the plasma membrane

Question 8

How can regulated secretion deliver extra membrane material

Answer 8

cytokinesis- when the cell divides into two

phagocytosis- when your membrane engulphs something it will get smaller and phagocytosis will counteract that

if the plasma membrane is damaged, extra membrane will be produced to repair it

Question 9

what three options do endocytosed proteins have

Answer 9

1. recycling to the same domain of the plasma membrane
2. transcytosis to the other domain of the plasma membrane
3. Degradation in the lysosome

Question 10

Cholesterol as an example of endocytosis

Answer 10

as cholesterol is moved into the cytosol, the LDL receptors will be recycled to the plasma membrane

Then, LDL will be degraded

finally, cholesterol moves to other parts of the body

Question 11

three types of membrane changes during vesicle trafficking

Answer 11

1. vesicle forms from donor membrane into the cytoplasm
2. vesicle fusion with target membrane
3. vesicles form from a donor membrane away from cytoplasm

Question 12

ESCRT Proteins

Answer 12

help form vesicles away from the cytoplasm

Question 13

example of when vesicles are formed away from cytoplasm

Answer 13

when viruses hijack cells, they pull cells used for cytokinesis to help membrane close off and fuse vesicle

ESCRT0-3 proteins will take turns transferring contents along membrane and ESCRT 3 will help form a structured vesicles with the cargo

Question 14

phosphoinositides

Answer 14

these lipids label different membrane domains

aka PIPs

Question 15

basic structure of PIPs

Answer 15

sugar head and a phosphate group, glycerol, and lipids making up the glycerophospholipid

Question 16

how are phosphoinositides named?

Answer 16

by which carbon is phosphorylated;
PI(3,4) P2

the final p is a count of how many carbons have been phosphorylated excluding the normal phosphate

Question 17

Fill in the blanks.

Phosphoinositides are interconverted by __________ and __________.

Answer 17

kinase and phosphatase

Question 18

How do Rabs and PIPs work together to give membranes different identities?

Answer 18

they activate the tethering proteins that recruit the appropriate proteins