Which of the following is not true of cell communication systems?
A) Cell signaling was an early event in the evolution of life.
B) Communicating cells may be far apart or close together.
C) Most signal receptors are bound to the outer membrane of the nuclear envelope.
D) Protein phosphorylation is a major mechanism of signal transduction.
E) In response to a signal, the cell may alter activities by changes in cytosol activity or in transcription of RNA.
Answer: C