buffers types of blood buffers mechanism of buffering system homeostasis role of blood buffers in regulation of homeostasis

1. University of Central Punjab
A “W4” Category University
Topic : Blood buffers
Subject : Biochemistry
Submitted To : Ma’am Afzia Anwar
Submitted By : Hafsa Nawaz
Reg No : M1F18BSCH0053
Semester : 4th

2. Buffers
Buffers are the chemical substances containing a weak acid and its salt or a weak
base and its salt, which resists change in pH from the addition of acid or a base.
Buffers are used to maintain a stable pH in solution, as they neutralize small
quantities of additional acid or base. Buffering capacity depends upon the absolute
concentration of salt and acid. Buffering is important in living system as a means
of maintaining a fairly constant internal environment, also known as homeostasis.
Blood buffers
The pH of blood is 7.35-7.45. The maintenance of the blood pH is important for
the proper functioning of our body and can be critical if not maintained. Changes
in pH below 6.8 and above 8.0 may result in death. The main buffers in blood are
bicarbonates, haemoglobin, plasma protiens and phosphates.
pH of blood buffers
The concentration of H2CO3 and HCO3 in the blood is 0.0024M and 0.024
respectively.

3. Types of blood buffers
Blood contains three buffer systems
1. Bicarbonates buffer
2. Phosphate buffer
3. Protien buffer
Bicarbonates buffer system:
It is important buffer system in the plasma is the bicarbonate-carbonic acid buffer
system (NaHCO3/H2CO3). It accounts for 65% of buffering capacity in plasma and
40% of buffering action in whole body. The pk of bicarbonate buffer is 6.1,
providing excellent buffering capacity around the normal ECF pH of 7.4.
The bicarbonate is regulated in the blood by sodium. When sodium bicarbonate
(NaHCO3), comes into contact with a strong acid, such as HCl, carbonic acid
(H2CO3), which is a weak acid, and NaCl are formed. When carbonic acid comes
into contact with a strong base, such as NaOH, bicarbonate and water are formed.
NaHCO3 + HCl → H2CO3+NaCl
(sodium bicarbonate) + (strong acid) → (weak acid) + (salt)
H2CO3 + NaOH→HCO3- + H2O
(weak acid) + (strong base)→(bicarbonate) + (water)
The base constituent, bicarbonate HCO-3 is regulated by the kidney
(metabolic component)

4. While the acid part, carbonic acid H2CO3 is under respiratory regulation
(respiratory components).
Bicarbonate ions and carbonic acid are present in the blood in a 20:1 ratio if the
blood pH is within the normal range. With 20 times more bicarbonate than
carbonic acid, this capture system is most efficient at buffering changes that would
make the blood more acidic. This is useful because most of the body’s metabolic
wastes, such as lactic acid and ketones, are acids.
Carbonic acid levels in the blood are controlled by the expiration of CO2 through
the lungs. In red blood cells, carbonic anhydrase forces the dissociation of the acid,
rendering the blood less acidic. Because of this acid dissociation, CO2 is exhaled
(see equations above). The level of bicarbonate in the blood is controlled through
the renal system, where bicarbonate ions in the renal filtrate are conserved and
passed back into the blood. However, the bicarbonate buffer is the primary
buffering system of the IF surrounding the cells in tissues throughout the body.
Importance
 Presence of bicarbonates in relatively high concentration
 The components are under physiological control, CO2 by lung and
bicarbonate by kidney
Phosphate buffer
Phosphates are found in the blood in two forms: sodium dihydrogen phosphate
(Na2H2PO4
−), which is a weak acid, and sodium monohydrogen phosphate

5. (Na2HPO42-), which is a weak base. When Na2HPO42- comes into contact with a
strong acid, such as HCl, the base picks up a second hydrogen ion to form the
weak acid Na2H2PO4
− and sodium chloride, NaCl. When Na2HPO42− (the weak
acid) comes into contact with a strong base, such as sodium hydroxide (NaOH), the
weak acid reverts back to the weak base and produces water. Acids and bases are
still present, but they hold onto the ions.
HCl + Na2HPO4→NaH2PO4 + NaCl
(strong acid) + (weak base) → (weak acid) + (salt)
NaOH + NaH2PO4→Na2HPO4 + H2O
(strong base) + (weak acid) → (weak base) + (water)
 The pK for the phosphate buffer is 6.7 which allow this buffer to function
within its optimal buffering range at physiological pH.
 Phosphates are major anions in intracellular fluid and minor anions in
extracellular fluid.
 If extra hydrogen ions enter the cellular fluid then they are neutralized by the
hydrogen phosphate ion.
 Importance
Phosphate buffer system is also important in buffering intracellular fluid because
the concentration of phosphate in this fluid is many times than in ECF.
Protien buffer system
Nearly all proteins can function as buffers. Proteins are made up of amino acids,
which contain positively charged amino groups and negatively charged carboxyl
groups. The charged regions of these molecules can bind hydrogen and hydroxyl
ions, and thus function as buffers. Buffering by proteins accounts for two-thirds of
the buffering power of the blood and most of the buffering within cells.
 Protien buffers are most important intracellular buffer and the most plentiful
buffer of the body.
 Protiens are extracellular buffers because they contain both acid and base
groups that can give up or take up H+.
 Protiens are extremely abundant in the cell.
 The more limited number of protien in the plasma reinforces the bicarbonate
system in the ECF.

6.  Haemoglobin of RBC’s is also an important buffer. It mainly buffers the fixed
acids, besides being involved in the transport of gases (O2 & CO2)
 Hemoglobin is the principal protein inside of red blood cells and accounts for
one-third of the mass of the cell. During the conversion of CO2 into
bicarbonate, hydrogen ions liberated in the reaction are buffered by
hemoglobin, which is reduced by the dissociation of oxygen. This buffering
helps maintain normal pH. The process is reversed in the pulmonary capillaries
to re-form CO2, which then can diffuse into the air sacs to be exhaled into the
atmosphere.
Mechanism of blood buffering system
 When any acidic substanceenters 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.
 On the other hand, when a basic substance enters the bloodstream, carbonic
acid reacts with the hydroxide ions producing bicarbonate ions and water.

7. 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.
Importance of blood buffers in regulation homeostasis
Homeostasis is defined as maintenance of relatively stable internal
environment. It is essential for functioning and survival of all cells. Blood
buffering is important in living system as means of maintaining fairly constant
environment (homeostasis). Small molecules such as bicarbonates and
phosphates, haemoglobin and other protiens helps in maintaining constant
internal environment. These all are Blood Buffers that helps regulating
homeostasis by maintaining blood acid-base balance.
The body has a wide array of mechanisms to maintain homeostasis in the blood
and extracellular fluid. The most important way that the pH of the blood is kept
relatively constant is by buffers dissolved in the blood. Other organs help
enhance the homeostatic function of the buffers.
 The kidneys help remove excess chemicals from the blood. It is the
kidneys that ultimately remove (from the body) H+ ions and other
components of the pH buffers that build up in excess. Acidosis that
results from failure of the kidneys to perform this excretory function is
known as metabolic acidosis. However, excretion by the kidneys is a
relatively slow process, and may take too long to prevent acute acidosis
resulting from a sudden decrease in pH (e.g., during exercise).
 The lungs provide a faster way to help control the pH of the blood. The
increased-breathing response to exercise helps to counteract the pH-
lowering effects of exercise by removing CO2, a component of the
principal pH buffer in the blood. Acidosis that results from failure of the
lungs to eliminate CO2 as fast as it is produced is known as respiratory
acidosis.