The Metabolism of LUCA (IMAGE) Heinrich-Heine University Duesseldorf Caption The Metabolism of LUCA. The research team investigated 402 biochemical reactions that are required for the biosynthesis of the molecular building blocks of life. Each circle represents one reaction, its color represents the energy that is released at each reaction. Green means energy is released, violet means energy is required. Credit HHU / Jessica Wimmer Usage Restrictions No restrictions. License Public Domain 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.