1. Amino acids R-groupsnon-polar polar acidic basic proteinscondensation between carboxylic acids and amines + + H2OH2O carboxylic acid amine amide

2. Amides amides resonance structure alanine glycine Ala-Gly +H 2 O dipeptide

3. Polypeptides “backbone” N1-N1- C1-C1-C1-C1-N2-N2-C2-C2-C2-C2-N3-N3-C3-C3-C3-C3- peptide bonds _ H _ H = O OH _ H _ H = O = O _ R _ R _ R N-terminal residue C-terminal residue biological activity = structure protein structure 4 levels

4. Primary structure sequence of amino acids hemoglobintransports O 2 and CO 2 4 protein chains 300 amino acids 6th amino acid from N-terminus Glu Val -CH 2 CH 2 -CO 2 H -CH(CH 3 ) 2 R Sickle cell anemia water soluble water insoluble

5. Primary structure study evolution  -chain 146 residues horses - humans = 26 pigs - humans = 10 gorillas - humans = 1 1 successful change / Primary structure - 10,000,000 years selective hydrolysis

6. Phe-Val-Asn-Gln-His His-Leu-Cys-Gly-Ser Gly-Ser-His-Leu-Val Gln-His-Leu-Cys His-Leu-Val-Glu Leu-Val-Glu-Ala Phe-Val-Asn-Gln-His His-Leu-Cys-Gly-Ser Gly-Ser-His-Leu-Val Gln-His-Leu-Cys His-Leu-Val-Glu Leu-Val-Glu-Ala

7. Secondary structure hydrogen bonding backbone groups H-bond donors N1-N1- C1-C1-C1-C1-N2-N2-C2-C2-C2-C2-N3-N3-C3-C3-C3-C3- _ H _ H = O OH _ H _ H = O = O _ R _ R _ R H-bond acceptors Two main secondary structures :  -helix  -sheet

8. Alpha helix Every C=Obonded to N-H4 residues away forms a helix core is backbone R-groups outside 3.6 amino acids per turn proline breaks helix = O C no H-bonding C = O N H

9. Beta sheet Every C=Obonded to N-Hfar apart in 1 o structure on different chains peptide chains extendedside-by-side maximal H-bonding for anti-parallel chains small R-groupsabove and below the sheet if not  -helix or  -sheet random coil

10. Secondary structure some proteins 1 o structure amino acid sequence 2 o structure  -helix  -sheet silk  -helix collagenbone, teethtriple helices keratinhair, skin, wool, hooves cross-linked with disulfide bonds

11. Disulfide bonds cysteine-CH 2 -SH S-HH-S CC H N C CC H N C reduced [O][O] SS CC H N C CC H N C oxidized

12. Protein function enzymesbiological catalysts immunoglobulinsantibodies transporthemoglobin hormonesregulation structuralkeratin, collagen motionactin, myocin function depends onstructure