What is the role of the phosphate buffer system?
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Answer:
The three major buffer systems of our body are carbonic acid bicarbonate buffer system, phosphate buffer system and protein buffer system.
Explanation:
The body's chemical buffer system consists of three individual buffers out of which the carbonic acid bicarbonate buffer is the most important.
CARBONIC ACID BICARBONATE BUFFER
Cellular respiration produces carbon dioxide as a waste product. This is immediately converted to bicarbonate ion in the blood. On reaching the lungs it is again converted to and released as carbon dioxide.
While in the blood , it neutralises acids released due to other metabolic processes. In the stomach and deudenum it also neutralises gastric acids and stabilises the intra cellular pH of epithelial cells by the secretions of bicarbonate ions into the gastric mucosa.
PHOSPHATE BUFFER SYSTEM
Phosphate buffer system operates in the internal fluids of all cells. It consists of dihydrogen phosphate ions as the hydrogen ion donor ( acid ) and hydrogen phosphate ion as the ion acceptor ( base ) . If additional hydroxide ions enter the cellular fluid, they are neutralised by the dihydrogen phosphate ion. If extra hydrogen ions enter the cellular fluid then they are neutralised by the hydrogen phosphate ion.
PROTEIN BUFFER SYSTEM
Protein buffer system helps to maintain acidity in and around the cells. Haemoglobin makes an excellent buffer by binding to small amounts of acids in the blood, before they can alter the pH of the blood. Other proteins containing amino acid histidine are also good at buffering.
The main purpose of all these buffers is to maintain proper pH within the body system so that all biochemical process can take place.
Phosphate Buffer System
Although the phosphate buffer system is not impor-tant as an extracellular fluid buffer, it plays a major role in buffering renal tubular fluid and intracellular fluids.
The main elements of the phosphate buffer system are H2PO4– and HPO4=. When a strong acid such as HCl is added to a mixture of these two substances, the hydrogen is accepted by the base HPO4= and con-verted to H2PO4–.
HCl + Na2HPO4 - - > NaH2PO4 + NaCl
The result of this reaction is that the strong acid, HCl, is replaced by an additional amount of a weak acid, NaH2PO4, and the decrease in pH is minimized.
When a strong base, such as NaOH, is added to the buffer system, the OH– is buffered by the H2PO4– to form additional amounts of HPO4= + H2O.
NaOH + NaH2PO4 - - > Na2HPO4 + H2O
In this case, a strong base, NaOH, is traded for a weak base, NaH2PO4, causing only a slight increase in pH.
The phosphate buffer system has a pK of 6.8, which is not far from the normal pH of 7.4 in the body fluids; this allows the system to operate near its maximum buffering power. However, its concentration in the extracellular fluid is low, only about 8 per cent of the concentration of the bicarbonate buffer. Therefore, the total buffering power of the phosphate system in the extracellular fluid is much less than that of the bicarbonate buffering system.
In contrast to its rather insignificant role as an extra-cellular buffer, the phosphate buffer is especiallyimportant in the tubular fluids of the kidneys, for tworeasons: (1) phosphate usually becomes greatly con-centrated in the tubules, thereby increasing the buffer-ing power of the phosphate system, and (2) the tubular fluid usually has a considerably lower pH than the extracellular fluid does, bringing the operating range of the buffer closer to the pK (6.8) of the system.
The phosphate buffer system is also important in buffering intracellular fluid because the concentrationof phosphate in this fluid is many times that in the extracellular fluid. Also, the pH of intracellular fluid is lower than that of extracellular fluid and therefore is usually closer to the pK of the phosphate buffer system compared with the extracellular fluid.
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Acids & Bases
Important Buffers in Living Systems
By David Stewart; Updated April 29, 2018

Motortion/iStock/GettyImages
A buffer is a chemical substance that helps maintain a relatively constant pH in a solution, even in the face of addition of acids or bases. Buffering is important in living systems as a means of maintaining a fairly constant internal environment, also known as homeostasis. Small molecules such as bicarbonate and phosphate provide buffering capacity as do other substances, such as hemoglobin and other proteins.
Several substances serve as buffers in the body, including cell and plasma proteins, hemoglobin, phosphates, bicarbonate ions, and carbonic acid. The bicarbonate buffer is the primary buffering system of the IF surrounding the cells in tissues throughout the body.
The three major buffer systems of our body are carbonic acid bicarbonate buffer system, phosphate buffer system and protein buffer system.
Explanation:
The body's chemical buffer system consists of three individual buffers out of which the carbonic acid bicarbonate buffer is the most important.
CARBONIC ACID BICARBONATE BUFFER
Cellular respiration produces carbon dioxide as a waste product. This is immediately converted to bicarbonate ion in the blood. On reaching the lungs it is again converted to and released as carbon dioxide.
While in the blood , it neutralises acids released due to other metabolic processes. In the stomach and deudenum it also neutralises gastric acids and stabilises the intra cellular pH of epithelial cells by the secretions of bicarbonate ions into the gastric mucosa.
PHOSPHATE BUFFER SYSTEM
Phosphate buffer system operates in the internal fluids of all cells. It consists of dihydrogen phosphate ions as the hydrogen ion donor ( acid ) and hydrogen phosphate ion as the ion acceptor ( base ) . If additional hydroxide ions enter the cellular fluid, they are neutralised by the dihydrogen phosphate ion. If extra hydrogen ions enter the cellular fluid then they are neutralised by the hydrogen phosphate ion.
PROTEIN BUFFER SYSTEM
Protein buffer system helps to maintain acidity in and around the cells. Haemoglobin makes an excellent buffer by binding to small amounts of acids in the blood, before they can alter the pH of the blood. Other proteins containing amino acid histidine are also good at buffering.
The main purpose of all these buffers is to maintain proper pH within the body system so that all biochemical process can take place.
Phosphate Buffer System
Although the phosphate buffer system is not impor-tant as an extracellular fluid buffer, it plays a major role in buffering renal tubular fluid and intracellular fluids.
The main elements of the phosphate buffer system are H2PO4– and HPO4=. When a strong acid such as HCl is added to a mixture of these two substances, the hydrogen is accepted by the base HPO4= and con-verted to H2PO4–.
HCl + Na2HPO4 - - > NaH2PO4 + NaCl
The result of this reaction is that the strong acid, HCl, is replaced by an additional amount of a weak acid, NaH2PO4, and the decrease in pH is minimized.
When a strong base, such as NaOH, is added to the buffer system, the OH– is buffered by the H2PO4– to form additional amounts of HPO4= + H2O.
NaOH + NaH2PO4 - - > Na2HPO4 + H2O
In this case, a strong base, NaOH, is traded for a weak base, NaH2PO4, causing only a slight increase in pH.
The phosphate buffer system has a pK of 6.8, which is not far from the normal pH of 7.4 in the body fluids; this allows the system to operate near its maximum buffering power. However, its concentration in the extracellular fluid is low, only about 8 per cent of the concentration of the bicarbonate buffer. Therefore, the total buffering power of the phosphate system in the extracellular fluid is much less than that of the bicarbonate buffering system.
In contrast to its rather insignificant role as an extra-cellular buffer, the phosphate buffer is especiallyimportant in the tubular fluids of the kidneys, for tworeasons: (1) phosphate usually becomes greatly con-centrated in the tubules, thereby increasing the buffer-ing power of the phosphate system, and (2) the tubular fluid usually has a considerably lower pH than the extracellular fluid does, bringing the operating range of the buffer closer to the pK (6.8) of the system.
The phosphate buffer system is also important in buffering intracellular fluid because the concentrationof phosphate in this fluid is many times that in the extracellular fluid. Also, the pH of intracellular fluid is lower than that of extracellular fluid and therefore is usually closer to the pK of the phosphate buffer system compared with the extracellular fluid.
Home »
Science »
Chemistry »
Acids & Bases
Important Buffers in Living Systems
By David Stewart; Updated April 29, 2018

Motortion/iStock/GettyImages
A buffer is a chemical substance that helps maintain a relatively constant pH in a solution, even in the face of addition of acids or bases. Buffering is important in living systems as a means of maintaining a fairly constant internal environment, also known as homeostasis. Small molecules such as bicarbonate and phosphate provide buffering capacity as do other substances, such as hemoglobin and other proteins.
Several substances serve as buffers in the body, including cell and plasma proteins, hemoglobin, phosphates, bicarbonate ions, and carbonic acid. The bicarbonate buffer is the primary buffering system of the IF surrounding the cells in tissues throughout the body.
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