Week 4: Protein Import/Edport

Question 1

What happens if the protein is water soluble?

Answer 1

Stay in the cytoplasm Go outside the world (secretion) Go to the nucleus Go to other organelles (mitochondria, chloroplasts, peroxisomes)

Question 2

How is the protein targeted to the membrane?

Answer 2

Need carrier to get the protein across the membrane

Question 3

What is a bacterial system called?

Answer 3

TAT (twin arginine translocation)

Question 4

What does TAT do

Answer 4

Take folded proteins across the membrane

Question 5

What does getting a soluble protein across the membrane mean?

Answer 5

Move charged residues through the hydrophobic interior of the membrane

Question 6

What are some views of the endoplasmic reticulum?

Answer 6

1) Immunofluoresence 2) scanning EM 3) transmission ER 4) model

Question 7

Which resolution is higher than immunofluorescence?

Answer 7

Scanning EM

Question 8

What are ribosomes associated with?

Answer 8

MRNA molecules

Question 9

What are rough ER defined by?

Answer 9

The presence of ribosomes bound to cytosolic surface

Question 10

What does polypeptide chain have?

Answer 10

Directionality N terminus and C terminus

Question 11

What does the secretory protein that contain a signal sequence direct ?

Answer 11

Emerging polypeptide and ribosome to the ER membrane

Question 12

What is a signal hypothesis?

Answer 12

The polypeptide moves into cisternal space of the ER through a protein-lined aqueous channel in the ER membrane

Question 13

What does the single recognition particle in mammals consist of?

Answer 13

6 different polypeptides + RNA (7s RNA)

Question 14

What does the SRP bind?

Answer 14

Both the SS on the nascent polypeptide chain and the ribosome

Question 15

How does the binding to the ER occur?

Answer 15

1) SRP and SRP receptor (in the RER) 2) Ribosome and Translocon

Question 16

How is the SRP released form the ER receptor?

Answer 16

SRP-ribosome-nascent-polypeptide binds to the cytosolic surface of the ER membrane

Question 17

What enzyme cleaves the signal peptide?

Answer 17

Signal peptidase

Question 18

What helps to fold the protein to pass through the lumen?

Answer 18

Chaperon

Question 19

What does targeting to the membrane require?

Answer 19

Signal polypeptide ( SRP and SRP receptor)

Question 20

What is required for protein to cross the membrane?

Answer 20

Translocon

Question 21

How is crossing the membrane done?

Answer 21

Co-translationally (protein crosses the membrane and at the same time it is synthesised)

Question 22

What was the matrix?

Answer 22

The cytoplasm of the bacterium

Question 23

What is the function of mitochondria?

Answer 23

Encodes and produces it’s own proteins

Question 24

What was the inter membrane space?

Answer 24

Periplasm of a gram negative bacterium

Question 25

What do mitochondria and chloroplast have in common?

Answer 25

Organelles that originated by endosymbiosis Make their own proteins/ most encoded in the nucleus and synthesised in the cytoplasm

Question 26

What is the difference between mitochondrial system and RER system?

Answer 26

There is no co-translational translocation across the membrane

Question 27

What is an example of a chaperone?

Answer 27

Hsp50

Question 28

What is the machinery that gets the polypeptide across the outer membrane ?

Answer 28

TOM complex

Question 29

What is TIM?

Answer 29

A hydrophobic protein channel in the IMM

Question 30

Inside the matrix what does the chaperone interact with ?

Answer 30

Polypeptide - helps to pull it through the membrane and then help it fold correctly

Question 31

What removes the presequence?

Answer 31

Peptidase

Question 32

What is the Translocon in outer membrane of chloroplast?

Answer 32

TOC

Question 33

What is the Translocon in inner membrane?

Answer 33

TIC

Question 34

What is stop transferase sequence?

Answer 34

Hydrophobic transmembrane segment containing at least 15 amino acids

Question 35

Where is stop transferase sequence located?

Answer 35

Remain in the membrane and is not passed through to the lumen

Question 36

What is the role of Translocon?

Answer 36

Responsible for determining the correct orientation of the protein in the membrane

Question 37

What orientation is the proteins synthesised in the RER ?

Answer 37

Inserted into the lipid bilayer in a predictable orientation determined by its amino acid sequence

Question 38

Where are carbohydrate chain located?

Answer 38

Cisternal side of the cytoplasmic membrane which become exoplasmic side of the plasma membrane following the fusion of vesicles with plasma membrane

Question 39

What will be found in the cytoplasm?

Answer 39

Glycerol, fatty acid and head group