Evidence that cell signaling evolved early in the history of life comes from __________.

Which of the following is likely to be a response by a receptor protein to an approaching signal molecule?

a) The receptor protein binds to the signal if it has a complementary shape.

b) If the signal is able to bind to the receptor it induces a change in the receptor protein's shape.

c) The change in the receptor protein's shape results in cellular action.

d) All of the above are correct.

Signal transduction pathways:

a) Are necessary for signals to cross the membrane.

b) Include the intracellular events caused by a signal binding to a receptor.

c) Include the extracellular events caused by a signal binding to a receptor.

d) Carry a signaling molecule to the nucleus of a cell.

What does it mean to say that a signal is transduced?

a) The signal enters the cell directly and binds to a receptor inside.

b) The physical form of the signal changes as it passes from the cell membrane to the intracellular target.

c) The signal is amplified, such that even one signal molecule evokes a large response.

d) The signal triggers a sequence of phosphorylation events inside the cell.