Chapter 19 Amino Acids and Proteins

1. Chapter 19 Amino Acids and Proteins 19.6Protein Hydrolysis and Denaturation

2. Protein Hydrolysis Protein hydrolysis • splits the peptide bonds to give smaller peptides and amino acids • occurs in the digestion of proteins • occurs in cells when amino acids are needed to synthesize new proteins and repair tissues

3. Hydrolysis of a Dipeptide • In the lab, the hydrolysis of a peptide requires acid or base, water, and heat. • In the body, enzymes catalyze the hydrolysis of proteins.

4. Denaturation Denaturation involves • the disruption of bonds in the secondary, tertiary, and quaternary protein structures • heat and organic compounds that break apart H bonds and disrupt hydrophobic interactions • acids and bases thatbreak H bonds between polar R groups and disrupt ionic bonds • heavy metal ions thatreact with S—S bonds to form solids • agitation,such as whipping, that stretches peptide chains until bonds break

5. Applications of Denaturation Denaturation of protein occurs when • an egg is cooked • the skin is wiped with alcohol • heat is used to cauterize blood vessels • instruments are sterilized in an autoclave

6. Learning Check What are the products of the complete hydrolysis of the tripeptide Ala-Ser-Val?

7. Solution What are the products of the complete hydrolysis of the tripeptide Ala-Ser-Val? The products are the three amino acids: alanine, serine, and valine.

8. Learning Check Tannic acid is used to form a scab on a burn. An egg is hard-boiled by placing it in boiling water. What is similar about these two events?

9. Solution Tannic acid is used to form a scab on a burn. An egg is hard-boiled by placing it in boiling water. What is similar about these two events? Acid and heat cause the denaturation of protein. They both break bonds in the secondary and tertiary structures of proteins.