A
buffer is an aqueous solution that resists changes in pH upon the addition of
an acid or a base. Also, adding water to a buffer or
allowing water to evaporate from the buffer does not change the pH of a buffer
significantly. Buffers basically constituent a pair of a weak acid and its conjugate
base, or a pair of a weak base and its conjugate acid.
Blood buffer
The bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance
of carbonic acid (H2CO3), bicarbonate ion (HCO3-), and carbon dioxide (CO2) in order to maintain pH in the blood and duodenum, among other tissues, to support proper metabolic function. Catalyzed by carbonic anhydrase, carbon dioxide (CO2)
reacts with water (H2O) to form carbonic acid (H2CO3),
which in turn rapidly dissociates to form a bicarbonate ion (HCO3-) and a
hydrogen ion (H+) as shown in the following reaction.
As with any buffer system, the pH is balanced by the presence of both
a weak acid (for example, H2CO3) and its conjugate base (for example, HCO3-) so that any excess acid or
base introduced to the system is neutralized.
Failure of
this system to function properly results in acid-base imbalance such as acidemia (pH<7.35) and alkalemia (pH>7.45) in the blood.
Regulation
When any
acidic substance enters the bloodstream, the bicarbonate ions neutralize the
hydronium ions forming carbonic acid and water. Carbonic acid is already a
component of the buffering system of blood. Thus hydronium ions are removed,
preventing the pH of blood from becoming acidic.
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On the other
hand, when a basic substance enters the bloodstream, carbonic acid reacts with
the hydroxide ions producing bicarbonate ions and water. Bicarbonate ions are
already a component of the buffer. In this manner, the hydroxide ions are
removed from blood, preventing the pH of blood from becoming basic.
As depicted below, in the process of neutralizing hydronium ions or hydroxide ions, the relative concentrations of carbonic acid and bicarbonate ions fluctuate in the blood stream. But this slight change in the concentrations of the two components of the buffering system doesn’t have any adverse effect; the critical thing is that this buffering mechanism prevents the blood from becoming acidic or basic, which can be detrimental.
Diagram of
blood pH maintained at approx. 7.4 by the carbonic acid – bicarbonate ion
buffering system
The pH of
blood is maintained at ~ 7.4 by the carbonic acid – bicarbonate ion buffering
system.
Why is it so critical to maintain the
pH of our blood?
Believe
it or not, if our blood pH goes to anything below 6.8 or above 7.8, cells of
the body can stop functioning and the person can die. This is how important the optimum pH
of blood is!
Enzymes are
very specific in nature, and function optimally at the right temperature and
the right pH; if the pH of blood goes out of range, the enzymes stop working
and sometimes enzymes can even get permanently denatured, thus disabling their
catalytic activity. This in turn affects a lot of biological processes in the
human body, leading to various diseases.
Diseases Related Blood
buffer
Basically, alterations
in blood pH cause acidosis or alkalosis, which is simply saying the same thing
as alterations in blood chemistry. These aren’t disease states themselves, but
may be the results of other disease states, or ingesting of certain substances.
The alterations in blood chemistry can cause fatal complications, by affecting
the oxygen disassociation curve, breathing (if respiratory is not the initial
source of the imbalance) and the equilibrium of countless reactions needed to
maintain body homeostasis.
The
bicarbonate buffer system plays a vital role in other tissues as well. In the
human stomach and duodenum, the bicarbonate buffer system serves to both
neutralize gastric acid and stabilize the intracellular pH
of epithelial cells via the secretion of bicarbonate ion into the gastric mucosa. In patients with duodenal ulcers, Heliobacter pylori eradication can restore mucosal
bicarbonate secretion, and reduce the risk of ulcer recurrence.
Conclusion
A buffer is an aqueous solution that
resists changes in pH when acids or bases are added to it. A buffer solution is
typically composed of a weak acid and its conjugate base. There are three major
buffer systems that are responsible for regulating blood pH: the bicarbonate
buffer system, the phosphate buffer system, and the plasma protein buffer
system. Of the three buffer systems, the bicarbonate buffer system is arguably
the most important as it is the only one that is coupled to the respiratory
system.
Chemistry plays an important role in
our surrounding environment, daily lives and biological systems. So buffers
being an integral part of inorganic chemistry also prove the importance of
applied chemistry in environment and other sectors.
Processes that take place in living
organisms are called physiological processes. Like blood circulatory system,
respiration etc. The internal pH of most living cells is close to 7.0. The pH
of human blood is 7.4. A blood pH of below 7 or above 7.8 can cause death
within minutes. So buffering of blood pH is very important to stabilize it
around 7.4. pH plays an important role in almost all biological processes.
Small change in pH, deceased or high pH can cause metabolic implications in
human body like acidosis and alkalosis. Where metabolism is involved there
would be definitely a need of buffer as within cells metabolism is associated
with the release of protons (H+) decrease in pH or uptake of protons
(H+) increase in pH.