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Biological Chemistry

Periodic Graphics

Periodic Graphics: Mucus, tears, and saliva

Chemical educator and Compound Interest blogger Andy Brunning looks at the biochemistry of our snot, spit, and tears.

by Andy Brunning, special to C&EN
February 26, 2023 | A version of this story appeared in Volume 101, Issue 7


An infographic describes the chemistry of mucus, tears, and saliva. The leftmost third describes the components of mucus, the middle third describes the components of tears, and the rightmost third describes the components of saliva.

To download a pdf of this article, visit

References used to create this graphic:

Bardow, Allan, Dennis Moe, Bente Nyvad, and Birgitte Nauntofte. “The Buffer Capacity and Buffer Systems of Human Whole Saliva Measured without Loss of CO2.” Arch. Oral Biol. (Jan. 2000). DOI: 10.1016/S0003-9969(99)00119-3.

Fenna, R., J. Zeng, and C. Davey. “Structure of the Green Heme in Myeloperoxidase.” Arch. Biochem. Biophys. (Jan. 1995). DOI: 10.1006/abbi.1995.1086.

Kirby, Anthony J. “The Lysozyme Mechanism Sorted—after 50 Years.” Nat. Struct. Mol. Biol. (Sept. 2001). DOI: 10.1038/nsb0901-737.

A collaboration between C&EN and Andy Brunning, author of the popular graphics blog Compound Interest

To see more of Brunning’s work, go to To see all of C&EN’s Periodic Graphics, visit


This graphic was updated on March 7, 2023, to correct the charge of the phosphate ions. It is 3–, not 2–.



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