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Chapter 20 Amino Acids and Proteins

Chapter 20 Amino Acids and Proteins. 20.6 Protein Structure: Tertiary and Quaternary Structure 20.7 Protein Hydrolysis and Denaturation. Tertiary Structure. The tertiary structure : Gives a specific overall shape to a protein.

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Chapter 20 Amino Acids and Proteins

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  1. Chapter 20 Amino Acids and Proteins 20.6 Protein Structure: Tertiary and Quaternary Structure 20.7 Protein Hydrolysis and Denaturation

  2. Tertiary Structure The tertiary structure: • Gives a specific overall shape to a protein. • Involves interactions and cross links between different parts of the peptide chain. • Is stabilized by Hydrophobic and hydrophilic interactions Salt bridges Hydrogen bonds Disulfide bonds

  3. Tertiary Structure

  4. Tertiary Structure • The interactions of the R groups give a protein its specific three-dimensional tertiary structure.

  5. Globular Proteins Globular proteins: • Have compact, spherical shapes. • Carry out synthesis, transport, and metabolism in the cells. • Such as myoglobin store and transport oxygen in muscle. Myoglobin

  6. Fibrous Proteins Fibrous proteins: • Consist of long, fiber-like shapes. • Such as alpha keratins make up hair, wool, skin, and nails. • Such as feathers contain beta keratins with large amounts of beta-pleated sheet structures.

  7. Quaternary Structure • The quaternary structure contains two or more tertiary subunits. • Hemoglobin contains two alpha chains and two beta chains. • The heme group in each subunit picks up oxygen for transport in the blood to the tissues.

  8. Summary of Structural Levels

  9. 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.

  10. 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.

  11. Denaturation Denaturation involves the disruption of bonds in the secondary, tertiary and quaternary protein structures. • Heat and organic compounds break apart H bonds and disrupt hydrophobic interactions. • Acids and bases break H bonds between polar R groups and disrupt ionic bonds. • Heavy metal ions react with S-S bonds to form solids. • Agitation such as whipping stretches chains until bonds break.

  12. 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 autoclaves.

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