Glossary of "Plant Biology (1st ed.)" by Graham et al. (2003)
- Organic molecules composed of carbon, hydrogen, oxygen, nitrogen and sulfur; macromolecules that are composed of amino acids.
Glossary of "Life (9th ed.)" by Sadava et al. (2011)
- Long-chain polymer of amino acids with twenty different common side chains. Occurs with its polymer chain extended in fibrous proteins, or coiled into a compact macromolecule in enzymes and other globular proteins.
- Graham, L. E., Graham, J. M. & Wilcox, L. W. 2003. Plant Biology. -xxxv + 497 pp. Pearson Education, Inc., Upper Saddle River.
- Sadava, D., Hillis, D. M., Heller, H. C. & Berenbaum, M. R. 2011. Life: The Science of Biology, 9th ed. -xliv + 1266 pp. Sinauer Associates, Inc., Sunderland.
- Block, R. J. 1935. On the nature and origin of proteins. Yale J. Biol. Med. 7(3): 235-252.
- Vickery, H. B. 1950. The origin of the word protein. Yale J. Biol. Med. 22(5): 387-393.