SEEGAR

Question 1

Proteins that are destined for secretion or insertion into cellular membranes are synthesized in the __________________.

Answer 1

Endoplasmic Reticulum (ER)

Question 2

Each protein contains a _________ element in its primary sequence that directs it to the correct organelle.

Answer 2

targeting

Question 3

____________ is the process of moving a protein across a membrane.

Answer 3

Translocation

Question 4

Translocation is energetically coupled to minimize ______________.

Answer 4

reverse translocation

Question 5

The ER signal sequence is typically located near the _________________ of the protein.

Answer 5

amino-terminus

Question 6

The ER signal sequence is often ______ during translocation into the ER.

Answer 6

cleaved

Question 7

The ER signal sequence is composed largely of __________ residues.

Answer 7

hydrophobic

Question 8

Attaching an ER signal sequence to a protein that is not normally secreted will direct it to the ____.

Answer 8

ER

Question 9

The ______________________ recognizes the ER signal sequence and directs the ribosome to the ER membrane.

Answer 9

Signal Recognition Particle (SRP)

Question 10

The SRP receptor (SR) is a heterodimeric transmembrane protein localized to the ____ that recognizes the SRP-Ribosome.

Answer 10

ER

Question 11

The interaction between SRP and SR is dependent on ___ hydrolysis.

Answer 11

GTP

Question 12

Binding of the SRP to the ribosome causes a ____ in translation.

Answer 12

pause

Question 13

The ____ is a gated ER pore that facilitates transport of the nascent polypeptide across the ER membrane.

Answer 13

Sec61 translocan

Question 14

_______ is the core subunit of the Sec61 translocon.

Answer 14

Sec61α

Question 15

Binding of the signal sequence to the Sec61 translocon causes the _____________ to open, allowing the polypeptide to enter the ER lumen.

Answer 15

pore

Question 16

The ___________________ cleaves the ER signal sequence from the protein.

Answer 16

ER signal peptidase

Question 17

The active site of the ER signal peptidase prefers ______________ residues in the P1 and P3 positions.

Answer 17

small hydrophobic

Question 18

________________________ occurs when a protein is translocated into the ER after translation is complete.

Answer 18

Post-translational translocation

Question 19

___, an Hsp70 family chaperone, binds to the unfolded translocating polypeptide to facilitate protein folding.

Answer 19

BiP

Question 20

BiP binding and protein folding are dependent on ___ hydrolysis.

Answer 20

ATP

Question 21

_________________________ span the membrane once and have their N-terminus in the ER lumen and their C-terminus in the cytosol.

Answer 21

Type-I transmembrane proteins

Question 22

_________________________ have their N-terminus in the cytosol and their C-terminus in the ER lumen.

Answer 22

Type-II transmembrane proteins

Question 23

_________________________ are similar to Type-II proteins, but their signal-anchor sequence is closer to the N-terminus.

Answer 23

Type-III transmembrane proteins

Question 24

_________________________ span the membrane multiple times, with alternating orientations of their N- and C-termini.

Answer 24

Type-IV transmembrane proteins

Question 25

_________________________ acts both as an ER signal sequence and a membrane anchor.

Answer 25

Signal-anchor sequence

Question 26

A _________________________ is a stretch of hydrophobic amino acids that halts translocation and anchors the protein in the membrane.

Answer 26

stop-transfer anchor sequence

Question 27

_________________________ are inserted into the ER membrane after translation is complete.

Answer 27

Tail-anchored proteins

Question 28

The ___ complex recognizes the exposed hydrophobic transmembrane α-helix at the C-terminus of tail-anchored proteins.

Answer 28

Get3

Question 29

___-dependent dimerization of Get3 is required for tail-anchored protein insertion.

Answer 29

ATP

Question 30

____ and ____ are ER membrane proteins that interact with Get3 to facilitate tail-anchored protein insertion.

Answer 30

Get1, Get2

Question 31

_________________________ are attached to the cell membrane via a GPI anchor.

Answer 31

GPI-anchored proteins

Question 32

The _________________________ is responsible for attaching GPI anchors to proteins.

Answer 32

GPI transamidase complex

Question 33

The GPI transamidase complex is a ___________ that cleaves the protein and attaches it to the GPI anchor.

Answer 33

Cys-protease

Question 34

_________________________ can be used to predict the transmembrane domains of a protein.

Answer 34

Hydropathy profiles

Question 35

Protein trafficking within a cell is determined by _________________________.

Answer 35

targeting and signaling sequences

Question 36

Proteins in the ER undergo _________________________ to promote proper folding.

Answer 36

post-translational processing and/or modification

Question 37

True or False: All proteins synthesized in the ER are secreted from the cell.

Answer 37

False. Some proteins synthesized in the ER are retained within the ER or transported to other organelles.

Question 38

True or False: The SRP binds to the ribosome and the ER signal sequence simultaneously.

Answer 38

True

Question 39

True or False: The Sec61 translocon is a passive channel that allows proteins to freely diffuse across the ER membrane.

Answer 39

False. The Sec61 translocon is a gated channel that requires energy for protein translocation.

Question 40

True or False: Glycosylation is a common post-translational modification that occurs in the ER.

Answer 40

True

Question 41

To move a protein across a bilayer, proteins are typically __________.

Answer 41

unfolded

Question 42

GPI stands for ________.

Answer 42

Glycosylphosphatidylinositol