Glossary of "The Cell (5th ed.)" by Alberts et al. (2008)
- Movement of a molecule across a membrane or other barrier driven by energy other than that stored in the electrochemical or concentration gradient of the transported molecule.
Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- Movement of a dissolved substance such as a mineral ion across a membrane that requires the expenditure of energy as ATP.
Glossary of "Biology (3rd ed.)" by Hardin & Bajema (1978)
- the expenditure of metabolic energy to move chemicals across a cell membrane against a concentration gradient.
- 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.
- Hardin, G. & Bajema, C. 1978. Biology, its Principles and Implications, third edition. -x + 790 pp. W. H. Freeman and Company, San Francisco.