If an animal cell suddenly lost the ability to produce GTP, what might happen to its signal ing system? (A) It would not be able to activate G proteins on the cytoplasmic side of the plasma membrane. (B) It would be able to carry out reception and transduction but would not be able to respond to a signal. (C) It would use ATP instead of GTP to activate G proteins on the cytoplasmic side of the plasma membrane. (D) It would not be able to activate receptor tyrosine kinases.