Ppt 2 proteins 2011

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Ppt 2 proteins 2011

  1. 1. Proteins
  2. 2. Protein Function <ul><li>Structural support – collagen </li></ul><ul><li>Storage of amino acid – egg white </li></ul><ul><li>Transport – hemoglobin </li></ul><ul><li>Hormonal – insulin </li></ul><ul><li>Receptor – nerve cell receptors </li></ul><ul><li>Contractile – actin & myosin </li></ul><ul><li>Defensive – antibodies </li></ul><ul><li>Enzymatic – digestive enzymes </li></ul>
  3. 3. Collagen and elastin provide a fibrous framework in animal connective tissues. Keratin is the protein of hair, horns, feathers, and other skin appendages. Support 1. Structural Examples Function Type of protein
  4. 4. Casein, the protein of milk, is the major source of amino acids for baby mammals. Plants have storage proteins in their seeds. Storage of amino acids 2. Storage
  5. 5. Hemoglobin, the iron-containing protein of vertebrate blood, transports oxygen from the lungs to other parts of the body. Other proteins transport molecules across cell membranes. Transport of other substances 3. Transport
  6. 6. Insulin, a hormone secreted by the pancreas, helps regulate the concentration of sugar in the blood of vertebrates. Coordination of an organism’s activities 4. Hormonal
  7. 7. Receptors built into the membrane of a nerve cell detect chemical signals released by other nerve cells. Response of cell to chemical stimuli 5. Receptor
  8. 8. Actin and myosin are responsible for the movement of muscles. Movement 6. Contractile
  9. 9. Antibodies combat bacteria and viruses. Protection against disease 7. Defensive
  10. 10. Digestive enzymes catalyze the hydrolysis of the polymers in food. Selective acceleration of chemical reactions 8. Enzymatic
  11. 11. Proteins <ul><li>Proteins are made of subunits of amino acids . </li></ul><ul><li>8 of these amino acids are essential – they must be </li></ul><ul><li>eaten in your diet (your body can’t synthesize them). </li></ul><ul><li>Proteins are the most diverse class of macromolecules due to 20 available amino acids. </li></ul>
  12. 12. Amino Acids
  13. 13. Amino Acids BASIC ACIDIC * * * * * * * * *
  14. 14. <ul><li>FOUR COMPONENTS: </li></ul><ul><ul><li>1. amino group </li></ul></ul><ul><ul><li>2. carboxylic acid (carboxyl) group </li></ul></ul><ul><ul><li>3. hydrogen atom </li></ul></ul><ul><ul><li>4. variable R group (or side chain) </li></ul></ul><ul><li>Amphiprotic: containing both acidic (COO - ) and </li></ul><ul><li>basic (NH 3 + ) functional groups </li></ul><ul><li>In aqueous solution: carboxyl group donates H + ion to </li></ul><ul><li>amino group </li></ul>Amino acid structure H | H 2 N – C – COOH | R H | + H 3 N – C – COO - | R +H 2 O
  15. 15. Peptides amide bond
  16. 17. Protein Organization <ul><li>Four layers of protein organization: </li></ul><ul><ul><li>primary (1°) structure </li></ul></ul><ul><ul><li>secondary (2°) structure </li></ul></ul><ul><ul><li>tertiary (3°) structure </li></ul></ul><ul><ul><li>quaternary (4°) structure </li></ul></ul>
  17. 18. Primary (1 ° ) Structure <ul><li>sequence of amino acids </li></ul><ul><li>polypeptide chain </li></ul>
  18. 19. Example: Sickle Cell Anemia <ul><li>abnormal hemoglobin develop because of a single amino acid substitution (change) </li></ul><ul><li>causes hemoglobin to crystallize, deforming the red blood cells and leading to clogs in blood vessels. </li></ul>Fig. 5.19 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings
  19. 20. Second (2 ° ) Structure <ul><li>H-bond between peptide bonds </li></ul><ul><li> -helix </li></ul><ul><li> -pleated sheets </li></ul><ul><li>not necessarily in all proteins </li></ul>
  20. 21. Tertiary (3 ° ) Structure <ul><li>provides protein a final 3-D structure </li></ul><ul><li>four major bond types between R groups of amino acids </li></ul><ul><ul><li>H-bonding </li></ul></ul><ul><ul><li>ionic bonding </li></ul></ul><ul><ul><li>hydrophobic interactions </li></ul></ul><ul><ul><li>covalent bond ( disulfide bridge ) </li></ul></ul>
  21. 22. Tertiary Structure: Proline kink <ul><li>Proline is the only amino acid in which the R group is attached to the amino group </li></ul><ul><li>Forms a natural kink in the polypeptide </li></ul><ul><li>Helps to shape tertiary structure </li></ul>
  22. 23. Tertiary (3 ° ) Structure
  23. 24. Quaternary (4 ° ) Structure <ul><li>fully functional protein requires all subunits present </li></ul><ul><li>not all proteins have quaternary structure </li></ul>
  24. 25. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.24
  25. 26. Protein Properties <ul><li>Proteins have optimal conditions at which they function. </li></ul><ul><li>When exposed to extreme conditions, proteins begin to unfold – denature . </li></ul><ul><li>Changes in pH, temperature and salt concentration can denature proteins. </li></ul><ul><li>If denaturation occurs moderately over time, returning to the original conditions may result in renaturation . </li></ul>
  26. 27. Example: Gastrin <ul><ul><li>1. Enzymes are active in the stomach. </li></ul></ul><ul><ul><li>2. Gastrin stimulates secretion of HCl acid. </li></ul></ul><ul><ul><li>3. When the pH is too low (acidic) gastrin denatures resulting in a _______ in pH. </li></ul></ul>From grade 11 Biology - Remember pepsin works at a pH of 2. Pepsin denatures at a pH of 5. Therefore it no longer can perform its function. Loss of shape = loss of function.
  27. 28. Hair
  28. 29. Protein Denaturation Video <ul><li>http://highered.mcgraw-hill.com/sites/0072943696/student_view0/chapter2/animation__protein_denaturation.html </li></ul>
  29. 30. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.26 <ul><li>The folding of a protein from a chain of amino acids occurs spontaneously. </li></ul><ul><li>The folding of many proteins is protected by chaperonin proteins that shield out bad influences. </li></ul>
  30. 31. Video: Protein Folding <ul><li>http:// www.wiley.com/legacy/college/boyer/0470003790/animations/protein_folding/protein_folding.htm </li></ul>
  31. 32. X-ray crystallography <ul><li>determines protein conformation </li></ul><ul><li>requires the protein in the form of a crystal </li></ul>Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 5.27 The pattern of diffraction of an X-ray by the atoms of the crystal can be used to determine the location of the atoms and to build a computer model of its structure

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