Question

Which of the following is associated with the termination of a cellular signal? (check all that apply)

A. ATP is converted to cyclic AMP
B. A G protein hydrolyzes GTP to GDP and Pi
C. Calcium ions are pumped into the smooth endoplasmic reticulum via active transport.
D. An enzyme breaks down an extracellular signal/ligand.
E. A chemical signal binds to the extracellular ligand binding domain of a receptor.

Answer 1

The termination of a cellular signal is facilitated by the inactivation of G proteins (option B), the reverse pumping of calcium ions (option C), and the breakdown of the extracellular signal/ligand (option D).

Step-by-step explanation:

Associated with the termination of a cellular signal are processes that reverse the initial signaling cascade. B. A G protein hydrolyzes GTP to GDP and Pi represents the inactivation of G proteins after they have fulfilled their role in signaling, turning them off to ensure the signal is not perpetuated indefinitely. C. Calcium ions are pumped into the smooth endoplasmic reticulum via active transport refers to the reversal of calcium release from internal stores, an important step in ceasing signal transduction. Finally, D. An enzyme breaks down an extracellular signal/ligand describes the degradation of the signal molecule itself, preventing further receptor activation.

Option A, ATP is converted to cyclic AMP (CAMP), and Option E, A chemical signal binds to the extracellular ligand binding domain of a receptor, are associated with signal initiation, not termination.