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Chapter 11 Assembly of Biomolecules We’ve looked at the construction of monomers for the four

Chapter 11 Assembly of Biomolecules We’ve looked at the construction of monomers for the four classes of biomolecules. Now we will turn to how some of those monomers are turned into useful cell components, using proteins as examples. CO 2 or other carbon source. Metabolic

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Chapter 11 Assembly of Biomolecules We’ve looked at the construction of monomers for the four

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  1. Chapter 11 Assembly of Biomolecules We’ve looked at the construction of monomers for the four classes of biomolecules. Now we will turn to how some of those monomers are turned into useful cell components, using proteins as examples CO2 or other carbon source Metabolic precursors Amino Acids Polypeptides Modification, transport, etc. NH3 Also SO4- Mature, Functional Proteins

  2. Protein Structure --- Proteins took over most of the catalytic and structural roles in cells because of the greater chemical diversity of amino acids (20) vs. nucleotides ( 4-5) --- Most proteins get their biological activity from their complex three dimensional shape --- The three dimensional shape of a protein is largely determined by its primary structure or amino acid sequence --- Most proteins have plastic three dimensional shapes that are constantly changing in at least small ways and the energy barriers to larger structural changes can be quite small Factors Affecting Protein Structure: Temperature, pH, solvent effects (ionic strength/ polarity)

  3. Levels of Protein Structure and the Forces That Hold Them Together Structural Force Components Level _____ ___________ 1 peptide bond amino acids 2 hydrogen bonds a-helices, b-sheets, turns, etc. 3 Hydrophobic forces domains H-bonds, ionic, disulfides 4 as in 3 above whole active protein

  4. Alpha-Helix Secondary Structure Elements Beta-Sheet

  5. Stringing Together Secondary Structural Elements (Tertiary Structure)

  6. Making Proteins Useful: (Getting Them Where They Need to be) Secretion: (General Secretory Pathway, GSP) --- Moving proteins across the cytoplasmic membrane --- Requires protein machinery and energy --- Protein is moved across membrane while unfolded Posttranslational modifications: Disulfide formation Signal Sequence Cleavage Co-Factor insertion Lipidation (Lipo-proteins) Cleavage

  7. Start of Protein “Signal Sequence” in proteins to be exported across the cytoplasmic membrane Cleavage

  8. Secretion Systems in Bacteria Family# of ProteinsEnergy SourceMoves ABC (I SP) 3-4 ATP proteins Sec (II SP) ca. 12 ATP & pmf proteins general secretory Fla/Path (III SP) 30+ ATP toxins Conjugative >10 ATP DNA (IV SP) OM AutoTrans. 1* ? proteins (V SP) Tat (VI SP) 2-4 pmf folded (RR system) proteins

  9. ABC Transporter

  10. General Secretory Pathway (Type II)

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