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pH and Biological Systems

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  1. pH and Biological Systems Dr. Nicholas Buker

  2. Module Learning Goals • Review of acids and bases • Understand the pH scale and calculations • Grasp buffers and their function • Study protein folding and observe denaturation • Recognize the importance of buffers in biological systems • Discuss and demonstrate the bicarbonate buffering system in our bodies

  3. Review: Acids and Bases Defined • BrØnsted-Lowry: Acids donate protons (H+ ions) into solution and bases accept protons • In solution, protons combine with water molecules to form hydronium ions (H3O+) acid base Review of acids and bases

  4. Review: Strong and Weak Acids • Strong acids dissociate nearly completely in solution • Weak acids partially dissociate in solution • Notice the difference in arrows used acid base Review of acids and bases

  5. Review: Conjugate Acids and Bases • The acidic and basic products are called conjugate acids and bases • Strong acids have very weak conjugate bases • Weak acids have conjugate bases strong enough to drive the reaction somewhat in the reverse direction acid base conjugateconjugate acid base Review of acids and bases

  6. The pH scale and Calculations • Logarithmic scale of acidity/basicity • pH < 7 is acidic, pH = 7 is neutral and pH < 7 is basic • [H3O+] > [OH-] acidic and [OH-] > [H3O+] basic pH scale and calculations

  7. Buffer Solutions • Solutions that change pH only slightly when acid or base is added using LeChatelier’s Principle • Ideally composed of roughly equal amounts of a weak acid and its conjugate base • Added acid is neutralized by the conjugate base • Added baseis neutralized by the weak acid Buffers and their function

  8. Protein Folding • Proteins begin as long chains that fold into very complex shapes • Process is driven primarily by IMF’s • The shape is critical to protein function • If the protein is misshapen, it will not function Protein folding and observe denaturation

  9. Protein Denaturation • Folded proteins are delicate and many things can cause misfolding, including pH changes • This process is known as denaturation and it can be lethal to organisms Protein folding and observe denaturation

  10. The Bicarbonate Buffer System • Blood pH is maintained around 7.4 using a buffer of carbonic acid (H2CO3) and the bicarbonate ion (HCO3-) • If blood is too acidic (acidosis), kidneys retain the basic bicarbonate ions • If blood is too basic (alkalosis), kidneys expel the basic bicarbonate ions Buffers in biological systems

  11. Why do we need buffers? • Strenuous activity creates CO2 which make the blood more acidic • Most foods are acidic and some are very acidic • Human ceviche? Buffers in biological systems