1. Biological Buffers

2. Buffers
Allow biological fluids to maintain relatively constant pH despite additions of acids or bases.

3. For Example: Blood
Human blood is normally pH 7.4

4. If you added a strong acid to water it could change from pH 7 to pH 2 very quickly.
When a strong acid is added to blood it only changes from pH 7.4 to 7.3. WHY?

5. Buffers Minimizes the changes in concentrations of H+ and OH-
Carbonic acid forms when carbon dioxide reacts with water

6. What’s the diff?
ACIDS ARE H+ DONORS
(also remove OH-)
BASES ARE H+ ACCEPTORS
(also add OH-)

7. Acid or Base?
HCl
NaOH
H2SO4

8. Acid or Base?
NaOH
HCl
acid
base
H2SO4
base
acid

9. Carbonic Acid
H2CO3 is an H+ donor (Acid)
Bicarbonate Ion
HCO3- is an H+ acceptor (Base)
Notice the double arrow in the equation above: that means the reaction can go both ways.

10. CO2 + H20 <=> H2CO3 <=> H+ + HCO3-
If the kidneys remove excess bicarbonate ions. the equilibrium is shifted to the right (so that more bicarbonate ions are produced to replace the lost ones), + more H+ are produced (lowers the pH).

11. CO2 + H20 <=> H2CO3 <=> H+ + HCO3-
If lots of CO2 produced (from lots of exercise), a lot of the CO2 ends up as H2CO3 (carbonic acid).
The carbonic acid then quickly dissociates to form H+ and HCO3-.

12. If H+ concentration falls,
That means the pH rises
That means it is becoming more basic
The reaction proceeds to the right as the carbonic acid dissociates to replenish H+ ions

13. If H+ concentration rises,
That means the pH lowers
That means it is becoming more acidic
The reaction proceeds to the left as the bicarbonate ion removes the H+ ions from the blood to form carbonic acid

14. OCEAN ACIDIFICATION
Carbonic acid is also formed in the ocean when atmospheric CO2 reacts with water.
This will remove the carbonate ion concentration in the ocean. NOTE CO2 LEVEL INCREASE.

15. But marine animals need carbonate ions for: coral and shells

17. What causes the increase of carbon dioxide levels in the atmosphere?
Burning of fossil fuels is a major source
Carbon Dioxide + rain water carbonic acid
Sulfur oxides + rain water sulfuric acid
Nitrogen oxides + rain water nitric acid
FORMS ACID PRECIPITATION:
Refers to rain, snow, or fog of a
pH lower than 5.2
(NORMAL RAIN IS ABOUT pH 5.6)

18. ACID PRECIPITATION

19. Why is the pH lower in the East?

20. Effects of Acid Precipitation
Fewer songbirds that eat snails
Thinner snail shells
Thinner egg shells
Destroys leaves

21. More Negative Effects Fish are very susceptible to pH changes.
Plankton and small invertebrates and young marine life are especially vulnerable.
Erode statues and buildings

22. Science Fair Project Ideas
Acid Rain Effects on Ocean Life
Or local aquatic life or local plants

23. CLEAN AIR ACT Passed 1990 Motor emission standards
Factory clean emission standards
Aircraft emission standards