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 CO 2 or other carbon source NH 3 Also SO 4 - Metabolic precursors Amino Acids Polypeptides Mature, Functional Proteins Modification, transport, etc.

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 StructuralForceComponents Level________________ 1 peptide bondamino acids 2 hydrogen bonds  -helices,  -sheets, turns, etc. 3 Hydrophobic forcesdomains H-bonds, ionic, disulfides 4 as in 3 abovewhole active protein

4. Secondary Structure Elements Alpha-Helix 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. Family# of Proteins Energy Source Moves ABC (I SP) 3-4ATP proteins Sec (II SP) ca. 12 ATP & pmf proteins general secretory Fla/Path (III SP) 30+ATPtoxins Conjugative >10ATPDNA (IV SP) OM AutoTrans. 1 * ?proteins (V SP) Tat (VI SP) 2-4pmffolded (RR system)proteins Secretion Systems in Bacteria

9. ABC Transporter

10. General Secretory Pathway (Type II)