Biochemistry Unit-1: Biological buffer systems

 Hello friends, in today's article, we see the biological buffer systems. In this system we see the four different types of biological systems, they are as follows

Biological Buffer Systems:

• Cells and organisms maintain a specific and constant cytosolic pH and keeping biomolecules in their optimal ionic state. (usually pH 7.0)
• In multicelled organisms, the pH of the extracellular fluids is also tightly regulated. the process of maintaining pH is constant that require system is called as biological buffer systems.
• Biological buffer is the mixture of weak acid and base, there are three important buffering systems of body fluids and in them, classification five biological buffer come. they are as follows

1. The bicarbonate buffer system
2. The protein buffer system
3. The phosphate buffer system
4. The Amino Acid buffer system

The Bicarbonate buffer system:

• The bicarbonate is the main extracellular buffer system, which provides a means for the necessary removal of CO₂ produced by tissue metabolism.
• This is the main buffer in blood plasma and consists of carbonic acid as proton donor and bicarbonate as a proton acceptor.

  
  H₂CO₃                                H⁺ + HCO₃^-

  This system has an equilibrium constant:                                                                             

• In blood bicarbonate system ratio is  [HCO₃^-]/[H₂CO₃ ] ratio of 20 to 1 is required to maintain pH 7.4 in blood plasma.

• If there is a change in the ratio in favor of H₂CO₃ is going to acidosis. this change can result from a decrease in [HCO₃^-] or an Increase in [H₂CO₃ ]

• There are two forms of acidosis 1) metabolic acidosis: metabolic acidosis is caused by a decrease in [HCO₃^-]. e.g. in uncontrolled diabetes with ketosis(starvation). 2) Respiratory acidosis: respiratory acidosis happens when there is an obstruction to the respiration system.

• If acidosis is not treated promptly the patient may go into a comma.

• Alkalosis: when H₂CO₃  concentration increase is called alkalosis. 1) Metabolic Alkalosis: This happens when the HCO₃^- fraction increase with little or no concomitant change in H₂CO₃. Severe vomiting or ingestion of excessive amounts of sodium bicarbonate con produce this condition. 2) Respiratory alkalosis: This happens when hyperventilation because of the excessive removal of CO₂ from the blood results in a decrease in [H₂CO₃ ]. Hyperventilation can result in anxiety, hysteria, prolonged hot bath, or lack of oxygen at high altitudes.

• alkalosis can produce convulsive seizures in children and tetany in adults. the pH Blood is maintaining at 7.4 when the ratio [HCO₃^-]/[H₂CO₃ ] becomes 20. buffer ratio remains by the respiratory elimination of H₂SO₃ as CO₂ or the urinary elimination of HCO^-₃. since cells contain a much lower amount of HCO^-₃, the importance of bicarbonate buffer inside the cell is negligible.

    2. The protein Buffer system: 

• The protein buffers are very important in the plasma and the intracellular fluids but their concentration is very low in cerebrospinal fluid, lymph, and interstitial fluids.
• The proteins exist as anions serving as a conjugate base at the blood pH 7.4 and form conjugate acids accepting H⁺. They have the capacity to buffer some H₂SO₃ in the blood.

    3.The phosphate Buffer System:

• this system, which acts in the cytoplasm of all cells, consists of H₂PO₄^-         as proton donor & HPO₄^2- as a proton acceptor.

• H₂PO₄^-        (draw both direction line)                             H⁺ + HPO₄^2-

• The phosphate buffer system work exactly like the acetate buffer system, except for the pH range in which it functions.

• This system is maximally effective at a pH close to its pKa of 6.86 & thus tends to resist pH changes in the range between 6.8 and 7.4.

• It is effective in providing buffering power in intracellular fluids. The concentration of phosphate buffer in the blood plasma is about 8% of that of the bicarbonate buffer. it is buffering capacity is much lower than bicarbonate in the plasma.

• The pH of intracellular fluids (6.0-6.9) is nearer to the pKa of the phosphate buffer. The buffering capacity of the phosphate buffer is highly elevated inside the cells and the phosphate is also effective in the Urine inside the renal distal tubules and collecting ducts.

• the ratio of [HPO₄^-2]/[H₂PO₄^-] tends to be changed by the formation of more H₂PO₄^-, there occurs the renal elimination of H₂PO₄^- for which ratio ultimately remains unaltered.

    4.The amino acid buffer system: This system also operates in humans, the amino acid content in humans, amino acids contain in their molecules both an acidic (-COOH) and basic(-NH2) group.

• They can be visualized as existing in the form of a neutral zwitterion in which a hydrogen atom can be pass between the carboxyl and amino groups the glycine may thus be represented as
  

• And the addition of HCl would result in the formation of amino acid hydrochloride, (1H-h2N-Ch2-COOH), but these substances would ionize in solution to some extent to form their corresponding ions. Hemoglobin plasma proteins act as buffers in a similar way.
• Amino acids differ in the degree to which they will produce the cation or anion form, in other words, a solution of amino acids is not neutral but is either predominantly acidic or basic, depending on which form is present in greater quantity. For this reason, different amino acids may be used as buffers for different pH values and a mixture of them possess a wide buffer range.

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    5. The Hemoglobin buffer Systems:

• these buffer systems are involved in buffering co2 inside erythrocytes. The buffering capacity of hemoglobin depends on its oxygenation and deoxygenation. Inside the erythrocytes, co2 combines with h2o to form carbonic acid under the action of carbonic anhydrase.
• at the blood pH 7.4, carbonic acid([HCO₃^-]) dissociates into H⁺ and [HCO₃^-], and needs immediate buffering.
  
  
  

This is all about the different types of the biological buffer system.

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