1. Pages 42 to 46

2.  Chemical composition  Carbon  Hydrogen  Oxygen  Nitrogen  Sulfur (sometimes)  Monomer/Building Block  Amino Acids (20 different amino acids)

3. Table 5-1

4. Fig. 5-UN1 Amino group Carboxyl group carbon

5. Peptide bond Fig. 5-18 Amino end (N-terminus) Peptide bond Side chains Backbone Carboxyl end (C-terminus) (a) (b) A peptide bond is the bond joining adjacent amino acids.

6.  Primary - peptide bond joining adjacent amino acids  Secondary - Hydrogen bonding between nonadjacent amino acids that creates an alpha helix or pleated sheets  Tertiary - bond formation between R-groups; clustering of hydrophobic (nonpolar) or hydrophilic (polar) R-groups, disulfide bridges, ionic bonding, grouping based on pH, etc… that results in 3-dimensional folding  Quaternary – joining of more than one polypeptide (not all proteins have this level)

7. Fig. 5-21 Primary Structure Secondary Structure Tertiary Structure  pleated sheet Examples of amino acid subunits + H 3 N Amino end  helix Quaternary Structure

8. Fig. 5-21b Amino acid subunits + H 3 N Amino end Carboxyl end 125 120 115 110 105 100 95 90 85 80 75 20 25 15 10 5 1

9. Fig. 5-21c Secondary Structure  pleated sheet Examples of amino acid subunits  helix

10. Fig. 5-21f Polypeptide backbone Hydrophobic interactions and van der Waals interactions Disulfide bridge Ionic bond Hydrogen bond

11. Fig. 5-21g Polypeptide chain  Chains Heme Iron  Chains Collagen Hemoglobin

12.  A slight change in primary structure can affect a protein’s structure and ability to function  Sickle-cell disease, an inherited blood disorder, results from a single amino acid substitution in the protein hemoglobin

13. Fig. 5-22 Primary structure Secondary and tertiary structures Quaternary structure Normal hemoglobin (top view) Primary structure Secondary and tertiary structures Quaternary structure Function  subunit Molecules do not associate with one another; each carries oxygen. Red blood cell shape Normal red blood cells are full of individual hemoglobin moledules, each carrying oxygen. 10 µm Normal hemoglobin     1234567 Val His Leu ThrPro Glu Red blood cell shape  subunit Exposed hydrophobic region Sickle-cell hemoglobin   Molecules interact with one another and crystallize into a fiber; capacity to carry oxygen is greatly reduced.   Fibers of abnormal hemoglobin deform red blood cell into sickle shape. 10 µm Sickle-cell hemoglobin GluPro Thr Leu His Val 1234567