Section 1
The Cells of Multicellular Organisms Communicate
Signal transduction pathwaysa. are necessary for signals to cross the membrane.b. include the intracellular events stimulated by an extracellular signal.c. include the extracellular events stimulated by an intracellular signal.d. are found only in cases where the signal can cross the membrane.
The function of a ____________ is to add phosphates to proteins, whereas a _______ functions to remove the phosphates.a. tyrosine; serineb. protein phosphatase; protein dephosphatasec. protein kinase; protein phosphatased. receptor; ligand