Intracellular Communication Intracellular Communication 1.
Some signal molecules can directly enter cells.
Hydrophobic molecules such as steroid hormones can enter cells because of their hydrophobic character. The receptor molecules for these hormones are inside the cells. The discovery of nitric oxide as a signal molecule provides an explanation for the ability of nitroglycerine to provide relief from the pains of angina. NO is released from nitroglycerine and relaxes blood vessels. NO often binds to the enzyme which converts GTP into cyclic GMP, an internal cell signal molecule.