Nutrition Science and Everyday Application - beta v 0.1

PROTEIN DIGESTION AND ABSORPTION 343
removed in a process called deamination, which occurs in the liver and kidneys. The nitrogen
is initially released as ammonia, and because ammonia is toxic, the liver transforms it into
urea. Urea is then transported to the kidneys and excreted in the urine. Urea is a molecule
that contains two nitrogens and is highly soluble in water. This makes it ideal for transporting
excess nitrogen out of the body.
Because amino acids are building blocks that the body reserves in order to synthesize
other proteins, more than 90 percent of the protein ingested does not get broken down
further than the amino acid monomers.
Self-Check
An interactive H5P element has been excluded from this version of the text. You can view it online here:
https://openoregon.pressbooks.pub/nutritionscience/?p=489#h5p-17
Attributions:
• Lindshield, B. L. Kansas State University Human Nutrition (FNDH 400) Flexbook.
goo.gl/vOAnR, CC BY-NC-SA 4.0
• “Protein Digestion and Absorption”, section 6.3 from the book An Introduction to
Nutrition (v. 1.0), CC BY-NC-SA 3.0
Image Credits:
• Fig 6.17. “Protein digestion in the human GI tract” by Alice Callahan is licensed
under CC BY 4.0; edited from “Digestive system diagram edit” by Mariana Ruiz,
edited by Joaquim Alves Gaspar, Jmarchn is in the Public Domain
• Fig 6.18. “Protein digestion in the stomach” from “Protein Digestion and
Absorption,” section 6.3 from An Introduction to Nutrition (v. 1.0), CC BY-NC-SA 3.0
• Fig 6.19. “Denaturation of proteins” by Alice Callahan is licensed under CC BY 4.0;
edited from “Process of denaturation” by Scurran is licensed under CC BY-SA 4.0
• Fig 6.20. “Enzymatic digestion of proteins” by Alice Callahan is licensed under CC BY
4.0; edited from “Process of denaturation” by Scurran is licensed under CC BY-SA