Unit 9 Problem Questions

Question 1

What do receptor tyrosine kinases do in a signal transduction pathway?

Answer 1

They bind an extracellular signal and convert it to an intracellular signal.

Question 2

What type of local signalling involves the direct contact between cell-surface molecules?

Answer 2

Juxtacrine signalling

Question 3

What is a common second messenger in signal transduction pathways?

Answer 3

Cyclic AMP (cAMP)

Question 4

What are mechanisms by which a cell can terminate a signal transduction pathway?

Answer 4

The ligand dissociates from the receptor (it is sequestered or degraded).

Receptors are internalized or degraded.

Second messengers (e.g., cAMP, Ca²⁺) are removed or broken down by specific enzymes.

Protein phosphatases remove phosphate groups added during the signalling cascade.