2. Acids, Bases, and Buffers (see page 20)

3. REMEMBER… A hydrogen atom (H) is just a PROTON and an ELECTRON So, a hydrogen atom without its electron (H+) is just a PROTON

4. Acids taste sour turn litmus paper red proton donors that release hydrogen ions (H + ) when they are dissolved in water, increasing the H + concentration e.g., HCl + H 2 O --> H 3 O + + Cl - (donates H + to H 2 O = H 3 O + hydronium ion) weak acids transfer few H+ to water e.g. CH 3 COOH + H 2 O --> CH 3 COO - + H 3 O + strong acids transfer many H+ to water e.g. HCl + H 2 O --> Cl - + H 3 O +

5. Bases bitter, slippery, and turn litmus paper blue proton acceptors that reduce the H + concentration of a solution E.g., Sodium hydroxide in water NaOH  Na + + OH - then, the OH - accepts H + OH - + H +  H 2 O thereby reducing the H + concentration E.g., Ammonia (NH 3 ) NH 3 + H 2 O  NH 4 + + OH - Then, OH - + H +  H 2 O

6. Water and pH can act as both a weak acid or a weak base. H-OH + H-OH --> H 3 O + + OH - important for determining pH pH = -log 10 [H+] in moles/litre e.g. If H 2 O has a H+ concentration of 1x10 -7 pH = -log 10 [1x10 -7 ] pH = 7 neutral 0--------------- 7--------------14 acidic basic (alkaline)

7. Practice E.g., Tonic Water has a H+ concentration of 3.1x10 -9 pH = -log 10 [3.1x10 -9 ] pH = 8.5 E.g., Wine has a H+ concentration of 2.5x10 -3 pH = -log 10 [2.5x10 -3 ] pH = 2.6

8. Neutralization Reactions acid + base ---> salt + water E.g., HCl + NaOH --> NaCl + H 2 O (donates H+) (accepts H+) (salt) (water)

9. Conjugate Acids and Bases (Bronsted-Lowry - proton theory of acids and bases) When an acidic substance loses a proton, it forms a base, called the conjugate base of the acid. When a basic substance gains a proton, it forms an acid called the conjugate acid of a base. e.g. HCl + NH 3 NH 4 + + Cl - Conjugate acid/base pair Conjugate acid/base pair acidbase Conjugate acid Conjugate base

10. Cells and pH Acidity is important to cells Even small changes of pH can drastically affect biological reaction Changes in pH can cause structural changes in proteins that can damage or destroy the proteins’ function

11. Acidosis Occurs if blood pH falls to within 7.1 and 7.3 (from 7.4). Symptoms include disorientation and fatigue. Blood pH < 7.0 can be fatal. Causes Airway obstruction, Hypoventilation (build up of carbon dioxide in blood creating carbonic acid) Drug overdose e.g., aspirin (acetyl salicylic acid)

12. Alkalosis Occurs when blood pH increases (becomes more basic). Symptoms: feeling dizzy, (alkalosis results in low CO 2 in the blood, the body assumes high O 2 and therefore constricts (narrows) blood vessels), feeling agitated, having muscle twitches (alkalosis results in low calcium levels – therefore nerve signals do not function properly) and vomiting. Blood pH > 7.8 can be fatal.

13. Causes Hyperventilation, high altitude over use of antacids

14. So… Organisms must control the pH of their cells with BUFFERS. Thomas’ buffers?

15. Buffers in the Body!

16. Buffers Maintain optimum pH ranges They are weak acids or weak bases Release H + when a fluid is too basic Take up H + when a fluid is too acidic E.g., In human blood carbonic acid and hydrogen carbonate (bicarbonate) ions keep blood close to its normal pH of 7.4 H 2 CO 3  HCO 3 - + H + + H +