Mitochondria, UC San Diego NCMIR (IMAGE) University of California - San Diego Caption This is a colorized transmission electron micrograph of cellular mitochondria, which produce a small molecule called ATP. Inside cells, ATP serves as an energy source but released outside the cell, it acts as a danger signal. Suramin inhibits the signaling function of ATP, eliminating the cell danger response associated with autism. Credit Photo by Thomas Deerinck, National Center for Microscopy and Imaging Research, UC San Diego Usage Restrictions Use photo credit as indicated 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.