Response to the Signal

Review Questions

What is the function of a phosphatase?

  1. A phosphatase removes phosphorylated amino acids from proteins.
  2. A phosphatase removes the phosphate group from phosphorylated amino acid residues in a protein.
  3. A phosphatase phosphorylates serine, threonine, and tyrosine residues.
  4. A phosphatase degrades second messengers in the cell.

Hint:

B

How does NF-κB induce gene expression?

  1. A small, hydrophobic ligand binds to NF-κB, activating it.
  2. Phosphorylation of the inhibitor Iκ-B dissociates the complex between it and NF-κB, and allows NF-κB to enter the nucleus and stimulate transcription.
  3. NF-κB is phosphorylated and is then free to enter the nucleus and bind DNA.
  4. NF-κB is a kinase that phosphorylates a transcription factor that binds DNA and promotes protein production.

Hint:

B

Apoptosis can occur in a cell when the cell is ________________.

  1. damaged
  2. no longer needed
  3. infected by a virus
  4. all of the above

Hint:

D

What is the effect of an inhibitor binding an enzyme?

  1. The enzyme is degraded.
  2. The enzyme is activated.
  3. The enzyme is inactivated.
  4. The complex is transported out of the cell.

Hint:

C

How does PKC’s signaling role change in response to growth factor signaling versus an immune response?

  1. PKC interacts directly with signaling molecules in both cascades, but only exhibits kinase activity during growth factor signaling.
  2. PKC interacts directly with signaling molecules in growth factor cascades, but interacts with signaling inhibitors during immune signaling.
  3. PKC amplifies growth factor cascades, but turns off immune cascades.
  4. PKC is activated during growth factor cascades, but is inactivated during immune response cascades.

Hint:

B

A scientist notices that a cancer cell line fails to die when he adds an inducer of apoptosis to his culture of cells. Which hypothesis could explain why the cells fail to die?

  1. The cells have a mutation that prevents the initiation of apoptosis signaling.
  2. The cells have lost expression of the receptor for the apoptosis-inducing ligand.
  3. The cells overexpress a growth factor pathway that inhibits apoptosis.
  4. All of the above.

Hint:

D