Glossary of "The Cell (5th ed.)" by Alberts et al. (2008)
- Organic molecule containing both an amino group and a carboxyl group. Those that serve as building blocks of proteins are alpha amino acids, having both the amino and carboxyl groups linked to the same carbon atom.
Glossary of "Evolution of Plants (2nd ed.)" by Willis & McElwain (2014)
- Organic acids from which proteins are built.
Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- The nitrogen-containing organic acids that can be linked together to form proteins.
Glossary of "Evolution (2nd ed.)" by Zimmer & Emlen (2016)
- The structural units that, among other functions, link together to form proteins.
Glossary of "Chemistry, A Molecular Approach (3rd ed.)" by Tro (2014)
- Organic compounds that contain a carbon atom, called the α-carbon, bonded to four different groups: an amine group, an R group, a carboxylic acid group, and a hydrogen atom.
- 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.
- Tro, N. J. 2014. Chemistry, A Molecular Approach, 3rd ed. - xxxviii + 1128 pp. Pearson Education, Inc., Upper Saddle River.
- Willis, K. J. & McElwain, J. C. 2014. The Evolution of Plants, 2nd ed. -ix + 398 pp. Oxford University Press, Oxford.
- Zimmer, C. & Emlen, D. J. 2016. Evolution: Making Sense of Life, 2nd ed. -xxxvi + 707 pp. Roberts and Company Publishers, Inc., Greenwood Village.