1. pH

2. Water & pH H + can split off from H 2 O, leaving OH – if [H + ] = [ - OH], water is neutral if [H + ] > [ - OH], water is acidic if [H + ] < [ - OH], water is basic pH scale how acidic or basic a solution is H 2 O  H + + OH –

3. pH Scale Acids= compounds that donate H + to a solution. Bases= compounds that accept H + from a solution. They may also remove H + from solutions by donating OH -.

4. 10 0 1 2 3 4 5 6 7 8 9 3 Amount of base added Buffering range 452 pH Buffers & cellular regulation pH of cells must be kept ~7 pH affects shape of molecules The shape of molecules affects their function pH affects cellular function Control pH by buffers reservoir of H + donate H+ when [H + ] falls absorb H+ when [H + ] rises

5. Figure 1: Average changes in the pH of water, buffer, and milk in response to incremental additions of HCL

6. Example: buffers in the blood pH of human blood is 7.4 Drops to 7.0 or increases to 7.8 are lethal after even a few minutes Blood maintains pH using these compounds: Blood maintains pH using these compounds: Bicarbonate HCO 3 - accepts --> H 2 CO 3 Carbonic acid H 2 CO 3 donates --> HCO 3 -