Quiz #1 in lecture multiple choice

Question 1

Signalling between cells usually results in the activation of protein __________
A) Lipases
B) Kinases
C) Proteases
D) Nucleases

Answer 1

Kinases

Question 2

What does a SH2 domain bind to?
A) Phosphorylated serines
B) Complementary SH2 domains on other proteins
C) Unphosphorylated transmembrane receptors
D) Phosphorylated tyrosines

Answer 2

Phosphorylated tyrosines

Question 3

The drugs taxol and nocodazole have opposite effects. Taxol binds tightly to microtubules and stabilizes them. In contrast, nocodazole prevents microtubule formation. Both are toxic and used as anticancer drugs. How can drugs with opposite effects on microtubule formation both be toxic?

Question 3

Mutations in the Apc gene occur in 80% of human colon cancers. Normal APC increases the affinity of the degradation complex for β-catenin, which in excess can enter the nucleus and promote transcription of key target genes for cell proliferation. Given this information, which category – oncogene or tumor suppressor – would you expect the Apc gene to belong to?

Answer 3

Tumor suppressor

Question 4

2. Which of the following mechanisms is NOT employed by I-Smads to negatively regulate Smad signaling?
   A). Competing with Smads for binding sites on the receptor
   B). Recruiting the ubiquitin ligase Smurf, leading to receptor degradation.
   C). Binding to nuclear pores, blocking Smads from entering.
   D). Binding to the co-Smad, Smad4, inhibiting it.
   E). Recruiting protein phosphatases, leading to receptor inactivation

Answer 4

C

Question 5

For the receptor tyrosine kinase (RTK)-Ras-MAP kinase pathway which is important for
Drosophila eye development, what would be a direct functional consequence of
mutating the SH3 domain of Drk?

A) Drk would no longer bind and recruit Ras-GEF.
B) Drk would no longer bind to phosphorylated tyrosine residues on activated
receptor tyrosine kinases.
C) The receptor tyrosine kinases would no longer be phosphorylated upon
binding to signaling molecules.
D) The receptor tyrosine kinases would no longer dimerize upon binding to
signaling molecules.
E) The receptor tyrosine kinases would no longer bind to signaling
molecules

Answer 5

A

Question 6

Which one of the following changes takes place when a skeletal muscle contracts?
A) Z discs move farther apart
B) Actin filaments contract
C) Myosin filaments move away from Z disc
D) Sarcomeres become shorter

Answer 6

D

Question 7

True or False? Motor neurons trigger action potentials in muscle cell membranes that open voltage-sensitive Ca2+ channels in T-tubules, allowing extracellular Ca2+ to enter the cytosol, this Ca2+ bind to troponin C, and initiate rapid muscle contraction.

Answer 7

False - the trigger calcium triggers something else thats let in the flood of calcium, its not the trigger calcium that directly leads to the flood in of EC calcium

Question 7

Which of the following proteins lacks a PH domain (Binds phospholipids)?
A). Sos (a Ras-GEF)
B). Grb2 (an RTK signaling adaptor)
C). Pleckstrin (a protein kinase C substrate)
D). Akt (protein kinase B)
E). PDK1 (phosphoinositide-dependent kinase)

Answer 7

B

Question 8

2. PI 3-kinase …
   A). is a membrane-associated tyrosine kinase.
   B). activates PDK1 by phosphorylating a serine residue on the protein.
   C). is counteracted by PTEN phosphatase.
   D). is only known to be activated by receptor tyrosine kinases.
   E). inhibits Akt.

Answer 8

C

Question 9

3. The actin-nucleating protein formin has flexible “whiskers” containing binding sites that help recruit actin subunits in order to enhance polymerization by this protein. What protein would you expect to bind to these sites?
   A). Thymosin
   B). Profilin
   C). Cofilin
   D). Gelsolin
   E). Tropomodulin

Answer 9

Profilin

Question 10

The role of ATP hydrolysis in actin polymerization is similar to the role of GTP hydrolysis in tubulin polymerization: both serve to weaken the bonds in the polymer and thereby promote depolymerization. True or False?

Answer 10

True