Intracellular components

Question 1

What kind of protein trafficking occurs on the nuclear membrane?

Answer 1

Gated transport

Question 2

What are the three types of protein trafficking?

Answer 2

Gated transport, protein translocation, vesicular transport

Question 3

How long, generally, are signal sequences

Answer 3

15-60 amino acids

Question 4

What is the function of a signal peptidase

Answer 4

to cleave the signal sequence from the finished protein after the complete sorting process

Question 5

What is the signal sequence for a protein destined for the ER?

Answer 5

5-10 nonpolar amino acids on the N-terminal sequence

Question 6

What is the signal sequence for a protein destined for the mitochondria?

Answer 6

positively charged amino acids that alternate with hydrophobic ones

Question 7

What is the signal sequence for a protein destined for peroxisomes?

Answer 7

3 characteristic amino acids at their C-terminus

Question 8

How much of the cell’s volume is occupied by membrane-enclosed compartments?

Answer 8

50%

Question 9

What proteins help the precursor mitochondrial protein stay unfolded in the cytosol?

Answer 9

Chaperone proteins fo the hsp70 family

Question 10

Within the mitochondria, where is the H+ ion concentration the greatest?

Answer 10

the intermembrane space

Question 10

What proteins help the unfolded protein fold when within the mitochondria?

Answer 10

mitochondrial hsp60

Question 11

Describe the difference between Co-translational and post-translational import of proteins into the ER.

Answer 11

Co- ribosome with half-baked protein attaches to the translocator and finishes protein synthesis, while funneling through the growing protein. Post- protein is completed by the time it gets to the translocator on the ER membrane.

Question 12

What types of proteins are fully translocated into the lumen of the ER?

Answer 12

water-soluble

Question 13

What guides a protein undergoing translation to the ER membrane?

Answer 13

signal recognition particle (SRP)

Question 14

What does the SRP bind to?

Answer 14

the ER signal sequence and the large ribosomal subunit, and later to the SRP receptor

Question 15

What is true about all ER signal sequences?

Answer 15

They have 8 nonpolar amino acids at the center.

Question 16

Where does the SRP attach on the large ribosomal subunit?

Answer 16

the elongation factor site, pausing translation

Question 17

What is a common ER translocator?

Answer 17

Sec61

Question 18

how many subunit comprise Sec61?

Answer 18

3

Question 19

What triggers the opening of the pore in Sec61>

Answer 19

ER signal sequence binding

Question 20

What are the three ways a transmembrane protein integrates in the ER membrane?

Answer 20

1. via a cleaved ER signal sequence
2. via an internal signal sequence that leads to C-terminus in the lumen
3. via an internal signal sequence that leads to T-terminus in the lumen

Question 21

Why, if there are more positively charged amino acids before the hydrophbic sequence, does the C-terminus enter the lumen?

Answer 21

The positive charge is attracted to the negative charge in the cytosol, causing it to stay outside.

Question 22

What would be included in the amino acid sequence of a Multipass protein in the ER membrane?

Answer 22

multiple start and stop transfer sequences.

Question 23

Where are the three most likely destinations for a water-soluble protein?

Answer 23

lumen of the ER, another organelle, or secretion

Question 24

What is an SRP made of ?

Answer 24

six polypeptide chains bound to a single, small RNA molecule

Question 25

The SRP’s signal sequence bind site is lined by what hydrophobic residue?

Answer 25

methionine