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Unit 1

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Unit 1

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  1. Unit 1 Biochemistry Part II

  2. Dissociation • Many substances dissociate (come apart) in water, in varying amounts. • In solution, some molecules are intact, while others are ionized (gain or lose electrons). • Water dissociates into ____ and ______ equally.

  3. Acids, Bases, Salts, and pH • Acid: a substance that yields H+ when it dissociates in water • Base: a substance that yields OH- when it dissociates in water (or accepts H+) • Salt: a substance in which the H+ of an acid is replaced by another positively charged ion • pH: the acidity or alkalinity (basic-ness)

  4. Acids • Acids add H+ to a solution, increasing the H+ concentration • Example: an acid (hydrochloric) dissociates: HCl  H+ + Cl-

  5. Bases • Bases can release an OH- or accept an H+ • Bases reduce the amount of H+ in a solution • Examples: OH- + H+ H2O NH3 + H+ NH4+

  6. Salts • Replace the H+ in an acid: • Example: HCl + Na  NaCl + H+

  7. pH • Formula: • pH = -log [H+] • [H+] means concentration of hydrogen protons • If the pH = 6 then the concentration of H+/liter is 10-6 in a solution • pH Scale: 0-14 • Acidic = <7, Basic = >7, Neutral = 7

  8. Buffers • Buffers are substances that take up or release H+ or OH- to prevent swings in pH • H2CO3 is an important buffer • H2CO3 dissociates to H+ and HCO3- • The H+ is a base acceptor • The HCO3- is an acid acceptor • Why are buffers important to living organisms?

  9. Water • H2O is bonded covalently (polar covalent) • This gives water some unique and useful properties

  10. Water Properties • A Powerful Solvent: able to dissolve anything polar. • Polar compounds dissolve making them hydrophilic (water-loving) • Example: Phosphates • Non-polar compounds do not dissolve making them hydrophobic (water-fearing) • Example: Lipids (fats)

  11. Water Properties (con’t) • Adhesion: The attraction between water and other substances • Cohesion: The attraction between water molecules and other water molecules • These cause ____________ action • Water attracts to and climbs polar substances due to adhesion • Water drags up more water with cohesion

  12. Water Properties (con’t) • High Surface Tension: water is attracted to itself (cohesion) more than it is attracted to the air around it. • High Specific Heat: it takes a lot of heat to increase the temperature of water and a great deal of heat must be lost to decrease the temperature of water. • High Boiling Point: lots of energy are required to break the hydrogen bonds in order to change water from a liquid to a gas

  13. Water Properties (con’t) • Good Evaporative Coolant: because it takes a lot of energy for water to change from a liquid to a gas, the loss of water vapor takes a lot of energy (heat) with it. • High Freezing Point • Lower Density as a Solid Than as a Liquid: maximum density = 4 C, while freezing is 0 C. • This is why ice floats and lakes freeze over, but not from the bottom up.