Information Pathway into the Cell (IMAGE) Paul Scherrer Institute Caption The cell interior is protected against external influences by the cell membrane. To channel information into the cell, which is transmitted by a messenger (H), special signal pathways exist. A: The messenger binds to a receptor in the membrane and activates it (illustrated here by the color change). In turn, the receptor activates a G protein. B: From this, the alpha subunit splits off and binds to the last part of the signal pathway, a protein called adenylyl cyclase. This transforms ATP -- which stores energy for the cell -- into so-called cyclic AMP (cAMP), an important secondary messenger in the cell. Credit Paul Scherrer Institute/Markus Fischer Usage Restrictions All media, such as photos, graphics and videos may only be used in the editorial context of these contents, naming the author. Archiving of this media is not permitted. License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.