ER, Golgi, Lysosomes & Endocytosis

Question 1

endomembrane system components

Answer 1

ER
Golgi
endosomes
lysosomes
cell surface

Question 2

Rough ER has:

Answer 2

ribosomes

Question 3

Protein targeted to ER recognised by:

Answer 3

signal sequence which is part of growing polypeptide chain

Question 4

Signal sequence recognised by:

Answer 4

Signal recognition particle (SRP)

Question 5

SRP binds to:

Answer 5

SRP receptor in ER membrane

Question 6

SRP receptor recruits:

Answer 6

Translocation channel

Question 7

Co-translational translocation transports ______ proteins into _______ & cleaves signal peptide with ______

Answer 7

soluble
ER lumen
signal peptidase

Question 8

Start-transfer and stop-transfer sequences are important for translocation of:

Answer 8

transmembrane and multi-pass membrane protein

Question 9

ER functions (2)

Answer 9

• disulphide bridge formation

- N-glycosylation

Question 10

Export from the ER is highly ______

Answer 10

regulated

Question 11

Chaperone proteins responsible for

Answer 11

protein folding

Question 12

Unfolded protein response

Answer 12

presence of unfolded protein trigger chaperone protein production and ER expansion
(feedback response)

Question 13

Retention in ER

Answer 13

some soluble proteins like chaperones have a KDEL C-terminal tag which allows them to remain in the ER

Question 14

Vesicle coat functions (2)

Answer 14

1. concentrates specific membrane proteins in specialised patch, creating vesicle membrane
2. moulds forming vesicle

Question 15

3 main coats:

Answer 15

• clathrin
• COPI
• COPII

Question 16

clathrin coated vesicles transport

Answer 16

from Golgi

from plasma membrane

Question 17

COPI & COPII coated vesicle transport

Answer 17

from ER

from Golgi cisternae

Question 18

coat assembly controlled by:

Answer 18

monomeric GTPases

Question 19

GTP-bound:

GDP-bound:

Answer 19

active

inactive

Question 20

GTP-binding proteins activated by ______ and inactivated by ______

Answer 20

GEFs

GAPs

Question 21

coat recruitment GTPase that controls COPII assembly on ER membrane

Answer 21

Sar1

Question 22

COPII vesicle formation:

Answer 22

Sar1 binds to Sar1-GEF embedded in ER membrane which causes Sar1 to bind GTP and become active

Question 23

Active Sar1

Answer 23

inserts amphipathic helix into cytoplasmic leaflet of ER membrane and is ready to recruit coat protein like Sec23 & Sec24

Question 24

Outer coat of COPII formed by

Answer 24

Sec13/31 which assembles the vesicle into a symmetrical cage

Question 25

coat disassembly

Answer 25

hydrolysis of bound GTP to GDP

Question 26

Rab proteins

Answer 26

- guide vesicle targeting - monomeric GTPases - cycle between membrane and cytosol

Question 27

GDP-bound Rab

Answer 27

inactive and bound to GDI

Question 28

GTP-bound Rab

Answer 28

active and tightly associated with a membrane

Question 29

SNARE proteins mediate:

Answer 29

membrane fusion

Question 30

3 types of SNARE protein

Answer 30

V-SNARES T-SNARES Q-SNARES

Question 31

SNARE protein structure

Answer 31

alpha helical domains which form a 4-helix bundle resulting in a trans-SNARE-complex

Question 32

trans-SNARE-complexes have to disassemble, which is catalysed by:

Answer 32

NSF (ATPase)

Question 33

Coats for anterograde and retrograde transport:

Answer 33

Antero: COPII Retro: COPI

Question 34

In the Golgi, transported molecules undergo an ordered series of:

Answer 34

covalent modifications

Question 35

cis-Golgi-network (CGN)

Answer 35

collection of fused vesicles arriving from ER

Question 36

trans-Golgi-network (TGN)

Answer 36

where proteins exit the Golgi in vesicles bound for cell surface or another compartment

Question 37

constitutive secretion

Answer 37

vesicles move directly from Golgi to plasma membrane

Question 38

regulated secretion

Answer 38

fusion of vesicles with plasma membrane depends on a signal

Question 39

Lysosomes

Answer 39

membrane-bound sacs of hydrolytic enzymes

Question 40

At what pH do acid hydrolases function?

Answer 40

4.5 - 5

Question 41

acid hydrolases e.g.

Answer 41

``` nucleases proteases glycosidases lipases phosphatases sulfatases phospholipases ```

Question 42

acidic pH in lysosome maintained by:

Answer 42

H+ influx into lumen by vacuolar H+ ATPases

Question 43

Metabolic transportes in lysosomal membranes deliver:

Answer 43

sugars, amino acids, nucleotides... back into cytoplasm

Question 44

Lysosomal functions (3)

Answer 44

- endocytosis - autophagy - phagocytosis

Question 45

lysosomal protein signal

Answer 45

mannose-6-phosphate

Question 46

M6P groups added exclusively to:

Answer 46

N-linked oligosaccharides of lysosomal enzymes

Question 47

M6P recognised by ___ in __

Answer 47

M6P receptor protein | TGN

Question 48

TGN packages lysosomal protein into _____ coated vesicles which are delivered to _____

Answer 48

clathrin | early endosomes

Question 49

addition of M6P groups catalysed by:

Answer 49

GlcNAc phosphotransferase

Question 50

When GlcNAc is cleaved off it leaves:

Answer 50

M6P signal marker

Question 51

lysosomal storage diseases:

Answer 51

I-cell disease | mucolipidosis

Question 52

clathrin-coated vesicle structure

Answer 52

3 large and 3 small subunits form triskelions which assemble into a convex framework of pentagons and hexagons

Question 53

adaptor protein in clathrin-coated vesicles

Answer 53

form discrete 2nd layer of coat between clathrin cage and membrane which traps transmembrane proteins that capture cargo in vesicle

Question 54

dynamin

Answer 54

- forms spring-like as clathrin-coated vesicle is forming | - GTP hydrolysis causes conformational change which separates vesicle from membrane

Question 55

macrophages

Answer 55

defend against infection by ingesting invading microorganisms and digesting them with lysosomal enzymes

Question 56

macromolecules bind to complementary transmembrane receptor protein, accumulate in clathrin-coated pits and enter cell as receptor-macromolecule complexes

Answer 56

receptor mediated endocytosis

Question 57

Receptor mediated endocytosis examples

Answer 57

- LDL receptor - Transferrin receptor - EGF receptor

Question 58

Lipoprotein particles are bound by:

Answer 58

Apoprotein B-100

Question 59

Transferrin cycle

Answer 59

gets iron into cell

Question 60

epidermal growth factor (EGF)

Answer 60

small signal protein that causes epidermal cells amongst others to divide

Question 61

When EGF binds to receptor:

Answer 61

- receptor becomes a dimer, which activates its' enzyme activity - tyrosine kinase phosphorylates itself - cells proliferate

Question 62

Mutated EGF receptor

Answer 62

proto-oncogene

Question 63

breakdown of membrane spanning protein with signalling end on cytosolic side involve:

Answer 63

multi-vesicular bodies

Question 64

(multi-vesicular bodies) vesicles produced into endosomes with help of:

Answer 64

- ubiquitin tags | - Escrt complexes

Question 65

multi-vesicular bodies break what rule?

Answer 65

topology rule