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Levels of Protein Structure 16.5

Levels of Protein Structure 16.5. Peptide/Protein Formation. Peptide: small, up to 50 AA Proteins: large, several 100 AA and/or multiple peptide chains grouped together Ribosomes translates m-RNA into AA sequence: 3 nucleotide = 1 AA. 1 o Primary Structure. Number and order of AA

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Levels of Protein Structure 16.5

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  1. Levels of Protein Structure16.5

  2. Peptide/Protein Formation • Peptide: small, up to 50 AA • Proteins: large, several 100 AA and/or multiple peptide chains grouped together • Ribosomes translates m-RNA into AA sequence: 3 nucleotide = 1 AA

  3. 1o Primary Structure • Number and order of AA • Reflected by peptide name • Example: Alanylglycylserine • 1o structure is the basis for all other levels of peptide/protein structure

  4. 2o Secondary Structure • Interaction between Amino- and Carboxyl groups residues from the peptide backbone forming • H-Bonds N-H…….O=C

  5. Alpha Helix b) Beta pleated sheet collagen, wool silk

  6. 3o - Tertiary Structure • Governed by R-side chain interactions • Hydrophobic interactions: At the center of a protein – two non-polar side chains are attracted (Ex: Ala and Leu) 2. Hydrophilic interactions: at the outskirts of a protein – two polar side chains, H-bonds (Ex: Serwith Thr)

  7. 3o structure 3. Salt Bridges (ionic bonds): attraction between acidic and basic side chains (Ex: Lys with Glu) 4. Disulfide Bridges: -S-S- covalent bond formation, two Cystein react, stabilizes the 3-D confirmation of large proteins, strongest

  8. 4o – Quaternary Structure • Multiple peptide chains aggregate together to form a large functional unit • Governed by R-side chain interactions (see 3o structure…) • Not all proteins have it

  9. Globular Proteins • Have a compact, spherical 3-D shape • Very stable, function as enzymes and transport molecules Hemoglobin Enzyme

  10. Fibrous Proteins • Long, thin, fiber like shapes • Used as structural components: wool, skin, scales, feathers keratin collagen

  11. Denaturation • Change in 3-D structure of a protein when exposed to heat/acids/bases/heavy metals/ organic solvents/agitation • Disrupts all levels of protein structure Exception: Dissulfide bridges remain, or new ones form…

  12. Denaturation

  13. Homework • Pgs 550 – 551 • #16.22 – #16.34 (even) • Skip #16.28 • Print the Enzyme Lab

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