B2 3

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B2 3

  1. 2. <ul><li>Unit B2 & 3: Cell Biology (Cell Compounds & Biological Molecules) </li></ul><ul><li>Students who have fully met the prescribed learning outcomes (PLO’s) are able to: </li></ul><ul><li>B2 </li></ul><ul><li>Describe the characteristics of water and its role in biological systems. </li></ul><ul><li>Describe the role of water as a solvent, temperature regulator, and lubricant. </li></ul><ul><li>Describe how the polarity of the water molecule results in hydrogen bonding </li></ul>
  2. 3. As well as….. <ul><li>B3 </li></ul><ul><li>Describe the role of acids, bases and buffers in biological systems in the human body. </li></ul><ul><li>Differentiate among acids, bases, and buffers. </li></ul><ul><li>Describe the importance of pH to biological systems in the human body. </li></ul>
  3. 4. So let’s get started…. <ul><li>B1: Water/H2O </li></ul><ul><li>Water makes up 60 (women) to 70 (men) % of the weight of most living organisms including all of us. </li></ul><ul><li>-Not an organic molecule, i.e. does NOT contain carbon. </li></ul><ul><li>-Water is an inorganic , polar molecule . </li></ul><ul><li>-Bonds between Hydrogen and Oxygen are covalent </li></ul><ul><li>i.e. they consist of pairs of shared electrons to become stable. </li></ul>- + +
  4. 6. Water: a polar molecule <ul><li>Electrons are shared unevenly </li></ul><ul><li>They spend more time orbiting oxygen than hydrogen. </li></ul><ul><li>This results in a slight positive charge on the hydrogen side and a slight negative charge on the oxygen side, therefore making H 2 O a polar molecule . </li></ul>
  5. 7. Note that the average electron density around the oxygen atom is about 10x that around the hydrogen atoms.
  6. 8. <ul><li>http://programs.northlandcollege.edu/biology/Biology1111/animations/hydrogenbonds.html (H2O animation) </li></ul>
  7. 9. Association of Two Water Molecules <ul><li>Hydrogen bonds form between adjacent water molecules </li></ul><ul><li>The covalent bonded positively charged H is attached to the negatively charged O by a H-bond . </li></ul>
  8. 11. Provincial Diagrams!!
  9. 12. <ul><li>The water will dissociate (separate) into ions (the bonds break when energy is supplied). </li></ul><ul><ul><li>E.g. H 2 O  H + + OH - (hydroxide ion) </li></ul></ul>
  10. 13. B2: Properties/Roles of H2O <ul><li>Because of its polarity and H-bonding , H 2 O has properties/roles beneficial to life. </li></ul><ul><li>1) Universal Solvent (Dissolving Agent) </li></ul><ul><li>The chemical reactions in our bodies occur in an environment where water is the solvent. </li></ul>
  11. 14. <ul><li>Due to its polarity , water molecules surround and breaks apart molecules. </li></ul><ul><li>As a result, the ions and molecules move around, collide and cause reactions to occur. </li></ul><ul><li>Water will then transport these ions and facilitate chemical reactions outside and inside cells. </li></ul>
  12. 15. Example of this …. <ul><li>Blood circulating dissolved ions, and molecules , causing reactions involving oxygen and carbon dioxide to be picked up and transported to and from tissues and lungs; blood circulating nutrients and ions to tissue cells and removing waste </li></ul>
  13. 16. http://www.coolschool.ca/lor/BI12/unit1/U01L02.htm (Check out Solvent animation ) <ul><li>2) Temperature Regulator </li></ul><ul><ul><li>The many H-bonds cause water to absorb/store large amounts of heat or release heat (energy) slowly, therefore protecting cells from rapid temperature change. </li></ul></ul>
  14. 17. 3.) Lubricant <ul><li>Lubricates cell parts and reduces friction. </li></ul><ul><ul><li>E.g. Tears, saliva, alveoli and pleural membranes in lungs, synovial joints. </li></ul></ul>
  15. 18. B3: Chemical Facts: Introduction <ul><li>1.) Dissociation </li></ul><ul><li>-Separating/breaking apart molecules; frequently in polar molecules. </li></ul><ul><li>E.g. H-O-H  H+ + OH- </li></ul><ul><li> (Water) lost e- gain e- </li></ul><ul><li>2.)Acids and Bases </li></ul><ul><li>-Acids and bases are a way of classifying compounds based upon what happens to them when they are placed in water. </li></ul><ul><li>Acids </li></ul><ul><li>Molecules that dissociate in H 2 O, releasing hydrogen ions (H+ ). </li></ul><ul><li>E.g. HCl (in H 2 O)  H+ + Cl- </li></ul><ul><li>(hydrochloric acid) </li></ul><ul><li>Bases </li></ul><ul><li>Molecules that release more hydroxide ions (OH-) in H 2 O or take up hydrogen ions (H+). </li></ul><ul><li>E.g. NaOH (in H 2 O)  Na+ + OH- </li></ul><ul><li> (sodium hydroxide) </li></ul><ul><li>or HCO 3- + H+  H 2 CO 3 </li></ul><ul><li> (bicarbonate ion) (carbonic acid) </li></ul>
  16. 19. 3.) pH : <ul><li>A scale (-log[H+]) that measures the [H+] (hydrogen ion concentration). </li></ul><ul><li>Indicates the strength of an acid or basic/alkaline solution. </li></ul><ul><li> [H+] acidic [OH-]basic/alkaline </li></ul><ul><li>0 7 14 </li></ul><ul><ul><ul><li>Less than 7 = an acid </li></ul></ul></ul><ul><ul><ul><li>Greater than 7 = a base/alkaline </li></ul></ul></ul><ul><ul><ul><li>7 = Neutral </li></ul></ul></ul><ul><ul><ul><li>pH scale runs in increments of 10. </li></ul></ul></ul><ul><li>E.g. 1x10-4 [H+] = pH 4 ( acidic ) </li></ul><ul><li> 1x10-7 [H+] = pH 7 ( neutral ), such as water 1x10-9 [H+] = pH 9 ( basic/alkaline ) </li></ul><ul><li>Animations of pH </li></ul><ul><li>http://www.purchon.com/chemistry/ph.htm </li></ul><ul><li>http://www.johnkyrk.com/pH.html </li></ul>
  17. 20. acidic neutral basic pH = <7 pH = 7 pH = >7
  18. 23. <ul><li>4.) Strengths </li></ul><ul><li>The strength of an acid depends on the [H+] ions and the strength of a base depends on the [OH - ] ions. </li></ul><ul><li>Therefore, the stronger the acid, the greater the [H+]; the stronger the base , the greater the [OH-]. </li></ul>
  19. 24. <ul><li>5.) Importance of pH to Biological Systems </li></ul><ul><li>In plant and animal cells, pH needs to be maintained within a narrow range to facilitate all chemical reactions. Animals must also control the pH of blood within a narrow range. </li></ul><ul><li>pH that is too acidic or basic causes proteins and enzymes to denature , </li></ul><ul><ul><li>i.e. their 3-D shape and biological properties are destroyed and all chemical reactions, active transport, gas exchange, digestion, protein synthesis, cell replication, nerve transmission etc. will NOT occur. (See B11) </li></ul></ul>
  20. 25. <ul><li>6.) Buffers </li></ul><ul><li>Slight changes in pH can be harmful. A buffer will minimize changes in [H+] and/or [OH-] by taking up excess H+ or OH- or donating H+ or OH-. </li></ul><ul><li>(A substance that acts as a hydrogen ion &quot;sponge&quot; and prevents drastic changes in pH when acid is added.) </li></ul>
  21. 26. <ul><li>Buffers functions to neutralize the pH of a solution/maintain a constant pH by combining with either H+ or OH- ions. </li></ul><ul><li>They are helpful since many reactions can occur only at pH’s which are not too acidic or basic. </li></ul><ul><ul><li>E.g. HCO 3 - + H+  H 2 CO 3 (using up excess H+) or </li></ul></ul><ul><ul><li>H 2 CO 3 + OH -  HCO 3 - (using up excess OH-) </li></ul></ul><ul><li>We have buffers in our blood, i.e. hemoglobin . Hb picks up and transports excess H+ in the reaction with carbonic anhydr ase . </li></ul>Buffers
  22. 27. Buffers Cont. <ul><li>We have buffers in our blood, i.e. hemoglobin . Hb picks up and transports excess H+ in the reaction with carbonic anhydr ase . </li></ul><ul><ul><li>E.g. H 2 O + CO 2  H 2 CO 3  HCO 3 - + H+  </li></ul></ul><ul><li>(carbonic acid) (bicarbonate ion) </li></ul><ul><li>Hb + H+  HHb </li></ul><ul><li> ( reduced Hb ) </li></ul><ul><li>During exercise we produce lots of CO 2 , HCO 3 - and therefore lots of H+. The Hb in our blood accepts the H+ (acts as a buffer resulting in HHb) causing blood pH to decrease , i.e. becoming less acidic. (See C9 and 10) </li></ul>

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