Midterm 1

Question 1

What is a covalent bond besides peptide bonds?

Answer 1

Disulfide (S-S) bond

Question 2

Where does an amino acid bind to a tRNA?

Answer 2

The 3’ end

Question 3

What is the function of EF-Ts?

Answer 3

It stimulates the exchange of GDP/GTP of EF-Tu

Question 4

What is right about eukaryotic translation initiation?
A. Start codon is translated into formylmethionine
B. Shine-Dalgarno sequence localizes ~10nt upstream to the start codon
C. Start codon is associated with TATA sequence
D. Initiation complex is assembled on the start codon
E. Initiation complex is assembled on the 5’ end of mRNA

Answer 4

E

Question 5

What does HSP stand for?

Answer 5

Heat-shock protein

Question 6

In Hsp70 and Hsp60 systems, which can work while the target protein is being translated?

Answer 6

Hsp70

Question 7

In Hsp70 and Hsp60 systems, which recognizes exposed hydrophobic region of protein?

Answer 7

Both

Question 8

In Hsp70 and Hsp60 systems, which recognizes multi-ubiquitinated protein?

Answer 8

Neither

Question 9

Nuclear export

Answer 9

1. Cargo molecule binds to a receptor called exportin
2. For cargo binding, the exportin must also be bound to Ran-GTP. Therefore cargo-exportin-Ran-GTP complex is formed in nucleus
3. The exportin interacts with nuclear pore and moves to cytosol
4. In cytosol, Ran GAP stimulates Ran-GTP to hydrolyze GTP to produce Ran-GDP, which can’t bind exportin anymore
5. As a result, exportin releases the cargo in cytosol, and goes back to nucleus without cargo
6. Ran-GDP also comes back to nucleus and then it transformed back Ran-GTP by the activity of Ran GEF

Question 10

What is most appropriate about the nuclear export of mRNA?

Answer 10

It needs to a helically-like protein

Question 11

Protein transport into ER lumen

Answer 11

1. For protein-transport into ER lumen, signal is recognized by SRP soon after the signal is exposed from ribosome
2. SRP binds the signal and pauses the translation
3. Then SRP is recognized by SRP receptor on ER membrane
4. This binding stimulates hydrolysis of GTP by SRP
5. After GTP is hydrolyzed, SRP leaves ribosome and signal sequence is transferred to translocon
6. Now translation is resumed, and newly formed polypeptide chain is pushed into ER
7. The ER signal sequence is cleaved by signal peptidase

Question 12

What amino acid can make a disulfide bond?

Answer 12

Cysteine

Question 13

Membrane lipid is mainly synthesized in ______

Answer 13

Smooth ER

Question 14

Newly synthesized lipid molecule is inserted first in _____ face of this organelle

Answer 14

Outside

Question 15

Lipid molecules are distributed to the other side of the lipid belayer by the enzyme called ____

Answer 15

Flippase

Question 16

The KDEL signal is bound to its receptor at Golgi but not at ER

Answer 16

True

Question 17

ER and Golgi membranes have H+ pump that are pumping H+ out

Answer 17

False

Question 18

KDEL receptor-ligand binding occurs only at lower pH

Answer 18

True

Question 19

If KDEL signal is removed from the cargo protein, the protein will eventually go to extra cellular space

Answer 19

True

Question 20

Membrane lipid is mainly synthesized in ______

Answer 20

Smooth ER

Question 21

Newly synthesized lipid molecule is inserted first in _____ face of this organelle

Answer 21

Outside

Question 22

Lipid molecules are distributed to the other side of the lipid belayer by the enzyme called ____

Answer 22

Flippase

Question 23

The KDEL signal is bound to its receptor at Golgi but not at ER

Answer 23

True

Question 24

ER and Golgi membranes have H+ pump that are pumping H+ out

Answer 24

False

Question 25

KDEL receptor-ligand binding occurs only at lower pH

Answer 25

True

Question 26

If KDEL signal is removed from the cargo protein, the protein will eventually go to extra cellular space

Answer 26

True