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Proteins

Proteins. H 2 O. Proteins. Structure: Elements: C, H, O, N monomer = amino acids 20 different polymer = polypeptide one or more polypeptide chains folded & bonded together large & complex complex 3-D shape. hemoglobin. growth hormones. Rubisco. H. O. | —C— |. H.

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Proteins

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  1. Proteins

  2. H2O Proteins • Structure: • Elements: C, H, O, N • monomer =amino acids • 20 different • polymer =polypeptide • one or more polypeptide chains folded & bonded together • large & complex • complex 3-D shape hemoglobin growthhormones Rubisco

  3. H O | —C— | H || C—OH —N— H Amino acids • Structure • central carbon • amino group • carboxyl group (acid) • R group (side chain) • variable • different for each aa • Results in unique chemical properties • like 20 different letters of an alphabet • can make many words (proteins) R

  4. Effect of different R groups: Nonpolar amino acids • nonpolar & hydrophobic

  5. Effect of different R groups: Polar amino acids • polar or charged & hydrophilic

  6. H+ donors Ionizing in cellular waters

  7. Sulfur containing amino acids • Formdisulfide bridges • covalent cross links betweens sulfhydryls • stabilizes 3-D structure H-S – S-H You wonderedwhy permssmell like rotten eggs?

  8. H2O peptidebond Building proteins • Peptide bonds • covalent bond between NH2 (amine) of one aa& COOH (carboxyl) of another • C–N bond dehydration synthesis

  9. 1. Primary Structure – aa sequence determined by gene (DNA) 4 Classes of Protein Structure Phenylalanine • **slight change in sequence can affect protein’s structure & its function just one aa change can make all the difference!**

  10. 2. Secondary Structure – folding due to interactions between adjacent (local) aa’sa. Alpha (α) Helix b. Pleated Sheet

  11. Secondary Structure of a Protein

  12. 3. Tertiary Structure • Overall primary and secondary structure • Hydrophobic interactions • H-bonds • Disulfide bridges • Ionic bonds between opposite charges

  13. 4. Quarternary Structure – more than one polypeptide bonded together **Increased complexity = increased stability!**

  14. Form determines function!!! Protein structure (review) R groups hydrophobic interactions disulfide bridges (H & ionic bonds) 3° multiple polypeptides hydrophobic interactions 1° amino acid sequence peptide bonds 4° 2° determinedby DNA R groups H bonds

  15. Conjugated Proteins • Protein backbone with nonprotein group attached • Chromoprotein – pigment molecule attachedEx: Hemoglobin • “Glyco” & “Lipo”Proteins – in cell membrane; carb or lipid attached – used in cell identity • Nucleoproteins – proteins wrapped in DNAEx: histones (in chromosomes)

  16. The Many Functions of Proteins • Enzymatic • Structural • Transport • Receptor • Signalling • Defense • Movement (contractile) • Storage

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