lecture 9

Question 1

Signal sequences that direct proteins to the correct compartment are

Answer 1

Encoded in the amino acid sequence of the protein

Question 2

Transport of proteins into the ER occurs:

Answer 2

during translation of the protein

Question 3

Which of the following proteins serves to stabilize the membrane of a transport vesicle during its formation:

Answer 3

Coat proteins

Question 4

There are at least two suspected origins for the evolution of internal membrane compartments

Answer 4

plasma membrane invaginations(endomembrane system)
endosymbionts
(mitochondria and chloroplasts)

Question 5

proteins must be sorted** by distinct processes that use different mechanisms and signals to

Answer 5

be able to go to diff. parts of the membrane

Question 6

energy inputs are required to move proteins across ______and to deform and _____ or fuse membranes.

Answer 6

membranes, separate

Question 7

A signal sequence that has a long chain of hydrophobic amino acids, followed by a few negativly charges A.a at n termanus would be imported

Answer 7

into the ER

Question 8

A signal sequence that has + charded A.a then - charged a.a then a hydrophobic A.a at the C ternimis would be

Answer 8

be in the lumen of the ER

Question 9

A signal sequence that has + charged a.a thta are dispersed in the sequence near the N terminus would be

Answer 9

inported in to the mitochondria

Question 10

A signal sequence that has a chain of + charged a.a would be

Answer 10

imported in the nucleus

Question 11

A signal sequence that has hydrophobic a.a interdispersed in a section of sequence would be

Answer 11

exported from nuleus

Question 12

a peroxiome has a signal sequence of

Answer 12

a single(very few) + charged a.a

Question 13

Once proteins are transported into the _____ , they cannot be exported to the cytosol again

Answer 13

nucleus

Question 14

Nuclear localization signals (NLS) receptors use

Answer 14

GTP hydrolysis

Question 15

____ _____Complexes allow proteins and mRNAs to traffic across the nuclear membrane

Answer 15

nuclear pore

Question 16

Classic experiment demonstrating nature of NLS

as a string of basic amino acids

Answer 16

used t-antigen

Question 17

Proteins are —— as they are transferred

across the mitochondrial membrane

Answer 17

unfolded

Question 18

signal sequence gets removed by _____ _____so this is unlike nuclear localization where shuttling can occur

Answer 18

signal peptidase

Question 19

Mitochondrial signal sequence fro in to ______

Answer 19

an amphipathic alpha helix

Question 20

Proteins being made can be directed for translocation into the ER by

Answer 20

Signal Recognition Particle (SRP) and the SRP receptor and a translocation channel

Question 21

____ ____ of signal sequence bearing proteins into the ER membrane

Answer 21

Cotranslational insertion

Question 22

Signal Recognition Particle associates with the nascent signal sequence, stalls the ribosome and aids _______________membrane at the SRP receptor

Answer 22

in docking on the ER

Question 23

Proteins are modified by ______ in the ER and Golgi. _____ bond formation is also catalyzed inthe ER.

Answer 23

glycosylation, Disulfide

Question 24

Chaperones are involved in

Answer 24

folding and proper membrane insertion in ER membrane

Question 25

The N-terminal signal sequence of many secretory

proteins is cleaved off by a

Answer 25

signal peptidase

Question 26

Start transfer and Stop transfer sequences specify insertion of ____ ______ ______ into the ER membrane
for single and multipass transmembrane domain proteins

Answer 26

hydrophobic transmembrane helices

Question 27

_____ _____ ______ have helped to study the

nature of the signals, their recognition and import processes

Answer 27

Cell free reconstituted systems

Question 28

Addition of ______ by oligosaccharide protein

transferases – note the high energy bond

Answer 28

glycosylations

Question 29

Protein folding in the ER is monitored and assisted
by _____ ____before the mature proteins
are permitted to be ____ _____ of the ER

Answer 29

chaperone proteins. trafficked out

Question 30

Unfolded Protein Response (UPR) a signaling pathway that helps cells maintain quality control over protein _____&_______by
increasing chaperone
activities.

Answer 30

folding and biogenesis

Question 31

Cystic fibrosis is frequently caused by

Answer 31

misfolded proteins are rapidly degraded regardless of whether they are at all functional. in the ER

Question 32

______ move soluble and membrane-associated proteins between cellular compartments

Answer 32

vesticles

Question 33

secretory pathway vesicle transport has what stypes of flow

Answer 33

“forward” flow = ER ->Golgi -> Plasma Membrane ->Lysosome

-“retrograde” flow – e.g. Golgi -> ER “retrieval

Question 34

Vesicles are formed and targeted by the action of

Answer 34

protein coats

Question 35

Coats serve to deform membranes so that they can be “pinched off” by

Answer 35

dynamin – GTP hydrolysis

Question 36

v-snares

Answer 36

are attached to the vesticle

Question 37

tsnares

Answer 37

attach to the destination membranes

Question 38

Rabs recognize _____ , then v-SNAREs and

t-SNAREs drive the fusion reaction and help provide membrane specificity

Answer 38

tethers

Question 39

COP coated proteins

Answer 39

transport to the ER and golgi

Question 40

The ____ face of the Golgi is a key sorting station as is the endosome

Answer 40

trans

Question 41

Another experimental approach complementary to genetics

- in vitro

Answer 41

is using reconstituted protein sorting in cell extrac

Question 42

Endocytosis of specific proteins, ligands, hormones and biomolecules can be

Answer 42

receptor-mediated

Question 43

the early endosome is like the Golgi in that it

Answer 43

is a sorting point for different destinations

Question 44

The pH of the lysosome is

Answer 44

Lower (more acidic) than the cytosol

Question 45

Lysosomal function is important to sphingolipid degradation.

Problems in these different enzyme functions cause

Answer 45

lysosomal storage diseases