Biological Buffers

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

For Example: Blood Human blood is normally pH 7.4

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?

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

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

Acid or Base? HCl NaOH H2SO4

Acid or Base? NaOH HCl acid base H2SO4 base acid

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.

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).

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-.

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

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

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.

But marine animals need carbonate ions for: coral and shells

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)

ACID PRECIPITATION

Why is the pH lower in the East?

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

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

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

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