Phys 02 13


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Phys 02 13

  1. 1. Objective 2.13 Levels of Protein Structure <ul><li>Describe the four levels of protein structure and discuss the importance of protein shape for protein function. </li></ul>
  2. 2. Protein Structure <ul><li>Amino acids are the smallest units of proteins </li></ul><ul><li>4 Levels of protein structure </li></ul><ul><ul><li>Primary: linear sequence of amino acids, encoded in the DNA sequence of a gene </li></ul></ul><ul><ul><li>Secondary: hydrogen bonds between atoms of the polypeptide backbone into a coil/helix, a sheet or a loop (random) </li></ul></ul><ul><ul><li>Tertiary: packing of coils and sheets into stable domains </li></ul></ul><ul><ul><li>Quaternary: multiple proteins combine </li></ul></ul>
  3. 3. 1 st Level of Protein Structure <ul><li>Primary: peptide bonds form the backbone of a protein or polypeptide chain. </li></ul><ul><li>Backbone = NCC-NCC-NCC </li></ul>
  4. 4. 2 nd Level of Protein Structure <ul><li>Secondary: H-bonds between the amino group and the carboxyl group of different amino acids </li></ul>
  5. 5. 3 rd Level of Protein Structure <ul><li>Tertiary: coiled coils, barrel of sheets and loops </li></ul><ul><li>R-groups: Nonpolar, Polar, Acidic and Basic </li></ul><ul><ul><li>Hydrogen bonds </li></ul></ul><ul><ul><li>Hydrophobic interactions </li></ul></ul><ul><ul><li>Covalent bonds </li></ul></ul><ul><ul><li>Ionic bonds </li></ul></ul>
  6. 6. 4 th Level of Protein Structure <ul><li>Some polypeptides form as a combination or complex of two or more individual proteins. </li></ul><ul><li>Multiple proteins are held together by interactions or bonds between the R groups (side chains) of one protein and the R groups of the second protein. </li></ul><ul><ul><li>Hydrogen bonds, hydrophobic interactions, ionic bonds, covalent bonds </li></ul></ul>
  7. 7. Protein Denaturation <ul><li>The function of a protein depends on its ability to bind to another molecule </li></ul><ul><li>Hostile environments such as heat, acid or salts will change a protein’s 3-D shape and destroy its ability to function </li></ul><ul><ul><li>raw egg white is vastly different after cooking </li></ul></ul>
  8. 8. The Importance of Protein Structure <ul><li>Structure determines the function </li></ul><ul><ul><li>Architecture of the cell </li></ul></ul><ul><ul><li>Enzymes facilitate metabolic reactions </li></ul></ul><ul><ul><li>Transport other proteins, oxygen, hormones, lipids </li></ul></ul><ul><li>Improper structure can impair the function </li></ul><ul><li>Long chain of amino acids, 100’s of amino acids in a single polypeptide…infinite possibilities. </li></ul><ul><li>Prevent improper interactions and conformations: chaperone proteins </li></ul><ul><li>Proteins are fragile (don’t shake the vial of vaccine or antibodies) </li></ul>
  9. 9. Hemoglobin, structure and function <ul><li>Polypeptide with quaternary structure – 4 polypeptides (2 alpha globin + 2 beta globin) </li></ul><ul><li>Hemoglobin forms a pocket for heme – iron-containing organic molecule </li></ul><ul><li>Binds and transports oxygen </li></ul>
  10. 10. Sickle Cell Anemia <ul><li>One amino acid different out of 146 </li></ul><ul><li>amino acids </li></ul><ul><li>Glutamate/Valine; genetic defect </li></ul><ul><li>Shape change, hemoglobin molecules form aggregates which deforms the red blood cells </li></ul><ul><li>Angular cells clog tiny blood vessels, halt circulation </li></ul><ul><ul><li>Circulatory problems </li></ul></ul><ul><ul><li>Heart failure </li></ul></ul><ul><ul><li>Compromised immune system </li></ul></ul><ul><ul><li>Anemia (diminished capacity to carry O 2 & limited circulation) </li></ul></ul>