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Understanding Acids and Bases in Biology

Learn the properties of acids and bases in solutions, including dissociation, pH measurement, types of acids, and biological importance. Explore bases, neutralization reactions, buffers, and the impact of pH on proteins.

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Understanding Acids and Bases in Biology

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  1. Properties of Acids & Bases Honors Bio: 2-3 Solutions

  2. Solutions • Solution: a mixture of two or more substances uniformly mixed together – can be PHYSICALLY separated. (often clear) • Ex: plasma, air, salt water, whipped cream • Solute: the substance dissolved. • Solvent: The dissolving substance; usually the greater amount. • Aqueous Solution: water is the solvent.

  3. Dissociation • The separating of a molecule into simpler molecules or ions. • In water, the force of attraction between water molecules (due to its POLARITY) or between water and other molecules is so strong that it can separate and remove atoms. • In water, this results in the formation of OH- and H+ ions (in EQUAL concentrations)

  4. Dissociation A very small percentage of the H2O molecules dissociate to form H+ and OH– ions. Most of the molecules in pure water remain intact as H2O.

  5. Acids • An acid is an aqueous solution that contains a greater concentration of H+ ions (compared to OH- ions). • Hydronium ions: form when free H+ ions react with other water molecules. • pH: measures the concentration of H+ ions in a solution.

  6. Acids (cont.) • Acids taste SOUR • pH <7 • Litmus RED • Weak acids: • Acetic acid (vinegar-CH3COOH) • Carbonic acid (H2CO3) • Lactic acid • Strong acids: • Hydrochloric Acid (HCl) • Nitric acid (HNO3) • Sulfuric Acid (H2SO4)

  7. Strong vs Weak Acids

  8. Weak Acids

  9. Biological Importance • Carbonic Acid (H2CO3) • Lactic Acid (CH3CH(OH)COOH) • Formic Acid (HCOOH) • Hydrochloric acid (strong acid) • Sea water, human blood, soft drinks • Active muscles, milk, microorganisms • Poison in stings from ants & nettle plants. • Stomach acid Mostly Weak Acids Biological Importance

  10. Bases (Alkaline) • An alkaline solution contains more hydroxide (OH-) than hydrogen (H+) ions. • Bases taste BITTER • Bases feel SLIPPERY • Ph>7 / Litmus turns BLUE • Ex: soap, baking soda, bleach, ammonia, “draino”

  11. Neutralization Reaction • Acid + Base Salt + H2O • Ex:HCL + NaOHNaCl + H2O • Buffer: chemical substances that neutralize small amounts of acids & bases. • Buffers keep pH constant. • Buffers are composed of a weak acid + conjugate base.

  12. Affect of pH on Proteins • Proteins DENATURE when pH changes • Buffer solutions are necessary to keep the correct pH for enzymes (proteins) in many organisms to work. Curdled Milk

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