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

H2SO4

NaOH

Acid or Base?

HCl

H2SO4

base acid

acidbase

• NaOH

Carbonic AcidH2CO3 is an H+ donor (Acid)

Bicarbonate IonHCO3- is an H+ acceptor (Base)

Notice the double arrow in the equation above: that means the reaction can go both ways.

Buffer Equilibrium• H2CO3 is in equilibrium with HCO3

− + H+

• H2CO3 HCO3− + H+

• (the direction of the reaction will go to making the concentrations even on both sides of the arrows)

• If you have a lot of carbonic acid the reaction will go toward the right.

• If you have a lot of H+ ions the reaction will go to the left.

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

Thinner egg shells

Thinner snail shells

Fewer songbirds that eat snails

Destroys leaves

More Negative EffectsFish 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 LifeOr local aquatic life or local plants

CLEAN AIR ACT

• Passed 1990• Motor emission standards• Factory clean emission standards• Aircraft emission standards