Protein Targeting - Exam Questions

Question 1

The endoplasmic reticulum synthesises proteins which will end up

a. secreted only
b. in mitochondria only
c. secreted, membrane-bound or inside an organelle
d. inside the nucleus only
e. in the cytoplasm

Answer 1

c. The ER synthesises proteins that will end up secreted, membrane-bound or inside an organelle.

Question 2

What determine the destination of a protein?

Answer 2

The signal sequence of the protein

Question 3

A protein destined for the interior of the endoplasmic reticulum
a. binds directly to a receptor on the ER membrane
b. binds to an SRP which binds to a receptor on the ER membrane
c. travels through a translocation channel post-translationally
d. is taken up by endocytosis
e. is made by a ribosome which is permanently bound to the ER
membrane

Answer 3

b. A protein destined for the interior of the endoplasmic reticulum binds to the SRP (signal recognition particle) which binds to a receptor on the ER membrane.

Question 4

A stop transfer sequence

a. is found on all proteins taken into the ER
b. is cleaved off the protein after it passes into the ER
c. is a hydrophilic region of the protein
d. becomes a permanent transmembrane region of a protein
e. permanently inactivates a transportation channel

Answer 4

d. A stop transfer sequence become a permamnent transmembrane region of a protein

Question 5

How do transport vesicles fuse with target membranes?

Answer 5

v-SNARES on the vesicle bind to complementary t-SNARE docking proteins on the target membrane.

Question 6

Where does glycosylation of proteins mainly occur?

Answer 6

In the golgi apparatus

Question 7

What mediates transport into and out of the nucleus?

Answer 7

The nuclear pores

Question 8

Entry into the nucleus is via

a. diffusion for all molecules
b. active transport for all molecules
c. diffusion for small molecules, active transport for large molecules
d. importins for small molecules, endocytosis for large molecules
e. diffusion for small molecules, importins for large molecules

Answer 8

e. Entry into the nucleus is via diffusion for small molecules and importins for large molecules.

Question 9

What are proteins destined for lysosome tagged with?

Answer 9

Mannose-6-phosphate

Question 10

Inclusion bodies are created when

a. Lysosomes cannot be formed
b. enzymes cannot be targeted to lysosomes
c. lysosomal enzymes cannot be synthesised
d. waste cannot be targeted to the cell membrane for exocytosis
e. lysosomes cannot take up hydrogen ions

Answer 10

b. Inclusion bodies are created when enzymes cannot be targeted to lysosomes