Glossary of "The Cell (5th ed.)" by Alberts et al. (2008)
- Extra energy that must be acquired by atoms or molecules in addition to their ground-state energy in order to reach a transition state and undergo a particular chemical reaction.
Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- The amount of energy that must be put into a chemical reactions to cause that reaction to proceed and to break and re-form the chemical bonds.
- Alberts, B., Johnson, A., Lewis, J. Raff, M., Roberts, K. & Walter P. 2008. Molecular Biology of the Cell, 5th ed. -xxxiv + 1616 pp. Garland Science, New York.
- Graham, L. E., Graham, J. M. & Wilcox, L. W. 2003. Plant Biology. -xxxv + 497 pp. Pearson Education, Inc., Upper Saddle River.