Proteins are present in every cell and support the body’s maintenance and growth. This lesson follows protein from digestion to reuse and explains how amino acids and protein structure determine what proteins do.
Protein digestion begins in the stomach. Hydrochloric acid creates an acidic environment that denatures proteins, unfolding their structures. The enzyme pepsin then breaks them into smaller polypeptides—chains made of amino acid residues.
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What happens to protein in the stomach during digestion?
Hydrochloric acid denatures or unfolds protein, and pepsin breaks it into smaller polypeptides.
What is a polypeptide?
A polypeptide is a linear chain of many amino acid residues; polypeptide chains form part or all of a protein.
What is the amino acid pool used for?
It provides available essential and nonessential amino acids that can be recombined to build proteins needed for growth and maintenance.
How do essential and nonessential amino acids differ?
Essential amino acids must be obtained from food. Nonessential amino acids can be synthesized by the body.
What determines a protein’s function?
The sequence of its amino acids and the way its molecule folds determine its structure and function.
Quiz questions
What does positive nitrogen balance indicate?Answer: Nitrogen intake exceeds nitrogen loss, indicating a net gain of body protein.
Which legume is identified as a complete protein?Answer: Soy
How does the body process excess protein that is not needed for protein synthesis?Answer: It excretes nitrogen in urine and may use or store the remaining carbon portion.
Why may protein intake be increased after a person begins dialysis?Answer: Protein is lost in the dialysate.
How should protein needs be managed in people with liver disease?Answer: They should be individualized; some people tolerate normal intake, while others may need targeted amino acid therapy.
Based on Nutrition for Nurses by Emerald Charity Bilbrew, Jody Vogelzang, Kelli Whittington (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.