Question

1- All of the following methods allow proteins to translocate to the nucleus and activate transcription EXCEPT:

Select one:

a. Phosphorylation of the target protein

b. Proteolytic cleavage of the target protein

c. Polyubiquitylation of the target protein

d. Polyubiquitylation of the inhibitor of the target protein

e. Protein conformation change of inhibitors, releasing a catalytic subunit

2- A negative feedback loop is ____, while a positive feedback loop is ___.

Select one:

a. A signaling pathway that is linear; a signaling pathway that is circular.

b. A signaling pathway that is circular; a signaling pathway that is linear.

c. A signaling pathway that ultimately targets an enzyme; a signaling pathway that ultimately targets transcription.

d. A signaling pathway that eventually causes the signal to stop; a signaling pathway that eventually causes the signal to continue.

e. A signaling pathway that eventually causes the signal to continue; a signaling pathway that eventually causes the signal to stop.

3- Which of the following statements about signaling is FALSE?

Select one:

a. Receptors do not interact with each other at the plasma membrane.

b. Multiple signaling pathways can end up regulating each other downstream of the signals.

c. After one molecule of hormone binds a receptor, multiple downstream messengers can be activated.

d. Signaling pathways often involve a series of phosphorylation events.

e. The amounts of hormones, receptors, and messengers dictate the level of cellular response.

Answer 1

1. c. polyubiquitylation of target protein

2. d. a negetive feedback loop is the signaling pathway that eventually causes the signal to stop whereas positive feedback loop is the signalling pathway that eventually causes the signal to continue.

3. a. receptors do not interact with each other at plasma membrane. This statement is false because dimerization of receptors occur at plasma membrane when a ligand binds to it in various signalling pathways like receptor tyrosine kinase pathway etc.