Endomembrane System II

Question 1

Default

Answer 1

protein export out of the rough ER and into the golgi

protein export out of the golgi and into the plasma membrane

Question 2

Cop II vesicle

Answer 2

a protein coat complex that transports protein out of the rough ER into the golgi

Question 3

Cop I vesicle

Answer 3

a protein coat complex that transports proteins from the cis golgi back to the rough ER.

Question 4

KDEL sequence

Answer 4

ER retrieval signal present in mammals and plants

ER lumen proteins

golgi —> rough ER lumen

Question 5

Cytoplasmic tails with arginine or lysine

Answer 5

ER retrieval signal resident transmembrane rough ER proteins

golgi –> rough ER

Question 6

ER retrieval signals (2)

Answer 6

KDEL sequence

Cytoplasmic tails with arginine or lysine

Question 7

What does ER retrieval signal mean?

Answer 7

(retrives from golgi and sends back to ER)

Question 8

Necessary signal

Answer 8

signal is necessary for protein to remain in ER; if it’s deleted it will be secreted

Question 9

Sufficient signal

Answer 9

signal transplanted to secreted protein and it will then remain in the ER

Question 10

‘bulk flow’

Answer 10

default transport of ER resident proteins out of the ER and to the golgi

Question 11

How are KDEL-receptors returned to the cis-golgi?

Answer 11

At rough ER pH is less acidic, favouring unbinding of KDEL-signal and KDEL-receptor. KDEL receptor packaged into COP II vesicle.

Question 12

What does golgi residency/retention signal mean?

Answer 12

retrieves from plasma membrane and sends back to golgi

Question 13

Whis is the golgi residency/retention signal?

Answer 13

TMD 17-20AA in length which is specific to golgi membrane thickness.

Short cytoplasmic tails

Question 14

LDL Particles

Answer 14

transport cholesterol to cells

Question 15

What is the golgi residency/retention signal?

Answer 15

TMD 17-20AA in length which is specific to golgi membrane thickness.

Short cytoplasmic tails

Question 16

Two protein layers of Clathrin Coated Complex

Answer 16

Clathrin complex (outer layer)
Adaptin complex (inner layer)

Question 17

Clathrin coated pits

Answer 17

patches of plasma membrane that concentrate receptor molecules and curve to form an invagination that buds off in endocytosis with receptor cargo inside the vesicle.

Question 18

How is cholersterol taken up by the cell?

Answer 18

1. cholesterol is transported in LDL particles which bind to an LDL receptor at the plasma membrane
2. Cholesterol is enocytosed via formation of a Clathrin Coated vesicle

Question 19

How do CCVs select cargo?

Answer 19

Adaptin 2 interacts with teh cytosolic tail of the receptor molecule that is holding teh cargo

Question 20

How do CCVs select cargo at specifically the plasma membrane?

Answer 20

Adaptin 2 interacts with the cytosolic tail of the receptor molecule that is holding the cargo

Question 21

FHC (Familial hypercholesterolaemia)

Answer 21

mutations in cytosolic tail/patients lack LDL receptor meaning CCVs cannot form and so cholersteral cannot be endocytosed, leading to heart disease since it isn’t taken up from the blood stream.

Question 22

Where are CCVs which have entered through the PM targeted to?

Answer 22

early endosome

Question 23

What happens to CCVs at the early endosomes?

Answer 23

Receptor and cargo dissociate

Receptors (in this case LDL receptors), are returned to the plasma membrane via the recycling endosome

Cargo travels to the late endosome and is mixed with lysosome proteins arriving from the golgi in the secretory patwhay. Both continue to the lysosome.

Question 24

Lysosomal Hydrolases are transported from

Answer 24

trans-golgi to late endosome

Question 25

Early endosome pH

Answer 25

6-6.5 lower than cytosolic pHso causes receptor and cargo to dissociate

Question 26

Where are lysosome hydrolyases made?

Answer 26

the rough ER

Question 27

What do enzymes of the cis-golgi do to lysosomal hydroloases?

Answer 27

Kinase phosphorylates a specific mannose residue on the N-glycan which creates a Mannose-6-phosphate signal

Question 28

How do enzymes of the cis-golgi recognise lysosomal hydroloases?

Answer 28

recognise a ‘signal patch’ in their tertiary structure

Question 29

Mannose-6-phosphate receptor

Answer 29

In trans-golgi and binds to the mannose-6-phosphate signal on the lysosomal hydrolase.

Question 30

When lysosomal hydrolases are transported from the trans-golgi to the late endosome, what are they transported in?

Answer 30

Clathrin Coated Vesicle

Question 31

How do CCVs select cargo at specifically the trans-golgi?

Answer 31

Adaptin 1 interacts with the Man-6P receptor