Shen Final review

Question 1

Substitution with which amino acid would generate an effect that is similar to phosphorylation?

Answer 1

Glutamic acid

Question 2

What bond determines the primary structure of proteins?

Answer 2

Peptide bonds

Question 3

What phospholipid is enriched on the cytoplasmic face of the ER?

Answer 3

Phosphatidylserine (PS)

Question 4

Compare the roles of Hsp70 and GroEL/ES in protein folding.

Answer 4

1. Hsp70 binds to hydrophobic patches on nascent protein as it is being synthesized on the ribosome. Prevents it from aggregating/folding before translation is complete.
2. Unfolded proteins have a chance to fold inside the protective sheltered chamber of GroEL/ES.

Question 5

The Na/K ATPase pump has a different affinity for the two ions depending on its conformation. Describe how this change in conformation and affinity drives the direction of transport of the two ions.

Answer 5

1. When it is open to the cytoplasm, it has a high affinity for Na and a low affinity for K.
2. When it is open to the extracellular space, it has a low affinity for Na and a high affinity for K.
3. This conformational change is regulated by ATP hydrolysis.

Question 6

A growth factor receptor is a transmembrane protein with three domains: an extracellular domain, a transmembrane domain, and a cytoplasmic domain. You observed that this receptor has two N-linked glycans (oligosaccharides). Which
domain(s) of the receptor will you likely find the glycans in? Explain.

Answer 6

Extracellular domain: N-linked glycosylation occurs inside of the ER; inside of ER is topologically equivalent to outside of cell.

Question 7

Which molecule does NOT pass through the Golgi apparatus to reach its final compartment?

a. EGF.
b. Insulin.
c. G protein-coupled receptor (GPCR).
d. Cytochrome c.
e. EGF receptor.

Answer 7

Cytochrome c

Question 8

Which of the following is a guanine nucleotide exchange factor (GEF)?

a. GPCR.
b. Rab.
c. Grb2.
d. Signal recognition particle (SRP).
e. NSF.

Answer 8

GPCR

Question 9

Which of the following will likely induce the ER stress response (unfolded protein response)? (4 points)

a. A chemical that inhibits lysosomal proteases.
b. A drug that interferes with the N-linked glycosylation of proteins.
c. An enzyme that digests O-linked glycans on the cell surface.
d. A mitochondrion-disrupting molecule that releases cytochrome c.

Answer 9

A drug that interferes with the N-linked glycosylation of proteins.

Question 10

Proteins are often transported between organelles in the cell. Which of these transport pathways is NOT mediated by membrane-bound vesicles? (4 points)

a. Golgi to lysosome.
b. ER to Golgi.
c. Cytosol to mitochondria.
d. Plasma membrane to endosome.

Answer 10

Cytosol to mitochondria

Question 11

The glucocorticoid receptor is a soluble cytoplasmic protein in the absence of its ligand. If you want to relocate the glucocorticoid receptor to the ER lumen and retain it in the ER as a soluble ER lumenal protein, what two sorting signals would you add to the protein? Why?

Answer 11

N terminal ER SS to target nascent polypeptide to ER.

KDEL for retrieval of receptor protein that accidentally escapes the ER.