pH Buffer Systems

Buffer Systems - Acid-Base Balance 


Buffers is defined as solution which resists change in (H+) ion concentration either on the addition of small amount of acid or base.


It is able to neutralize small amount of added acid or base, thus maintaining of pH of solution relatively stable.


Buffers can absorb excess H+ ions or OH ions, thereby maintaining  pH in the solution.

Buffer System is solution or substance that has the ability to maintain PH and bring it back to optimum value by addition or removal hydrogen ion.


Know-how is acid-base balanced in the body?

Strong acid – It releases large amount of hydrogen ions.


Weak acid – It release small amount of hydrogen ions.


Strong bases – It accept large amount of Hydrogen ions.


Weak bases – It accept small amount of Hydrogen ions.


Buffers are the first line of defence against the acid and base load in the body. The function of buffer is to resist change in PH of solution.


For example - Blood in the human body is buffer solution.


The buffer that maintain and regulate the pH of human blood involves carbonic acid (H2CO3), bicarbonate ion (HCO3), and carbon dioxide (CO2). 

Major Buffer System in Human Body

Three major buffer systems in body fluids are –

1. Carbonic acid bicarbonate buffer system

2. Protein buffer system

3. Phosphate buffer system


1. Intracellular fluid (ICF)



A. Phosphate buffer system



Phosphate buffer system operates in the internal fluids of all cells.


It is main intracellular buffer, they are Important for maintaining intracellular pH and regulating urine pH.


Phosphate buffer system has two elements-


1. H2PO4

2. HpO4 -



1. Phosphate buffer system major role in the eliminating of H+ via the kidney.  

3. It stabilizes the PH of blood and Urine.

4. It has major role in buffering renal tubular fluid and intracellular fluids.




2. Extracellular fluid (ECF)


A. Carbonic acid-bicarbonate buffer system



Carbonic acid-bicarbonate buffer system most important buffer for maintaining acid-base balance in the blood.


Carbonic acid-bicarbonate buffer system directly linked up with respiration.



Carbonic acid-bicarbonate buffer system is an acid-base homeostatic mechanism involving the balance of-  


1. Carbonic acid (H2CO3), carbonate ion and,

2. Carbon dioxide CO2


Bicarbonate buffer systems are regulated as follows-


1. Bicarbonate ion by kidney (metabolic component)

2. Co2 by respiration system (respiratory component)



It Involve in maintaining PH in blood and duodenum. Bicarbonate buffer acts to regulate pH in the small intestine. In the human stomach and duodenum, the bicarbonate buffer serves to neutralize gastric and stabilize intracellular pH of epithelial cell via secretion of bicarbonate ion into gastric mucosa.  




3. Protein Buffer System

Protein buffer system help to maintain acidity in and around cells.


A. Haemoglobin buffer system (RBC only)

Haemoglobin makes an excellent buffer by binding to small amounts of acids in blood , before they can alter of PH of blood.


B. Amino acid buffers (all proteins)


Protein containing amino acid Histidine(present in albumin and hemoglobin) are also good at buffering.


C. Plasma protein buffers


Albumin, alkaline act as buffer in plasma.




Different Buffer Systems Role in Different part of Body


1. Interstitial fluid


Major buffers


Bicarbonate buffer system


Minor buffers


Protein buffer system

Phosphate buffer system


2. Blood



Bicarbonate buffer system

Haemoglobin buffer system




Plasma buffer system

Protein buffer system

Phosphate buffer system


3. Intracellular fluid



Protein buffer system

Phosphate buffer system


4. Urine



Ammonia buffer

Phosphate buffer system



Check out here 4 types of acid-base imbalance in the body?

Regulation of Acid-Base Balance



An organ involved in acid-base balance in the body-


1. Blood -  Excellent buffering agent

2. Kidney -  Carry out excretion of acids and conservation of base

3. Lung - Elimination of CO2

4. Intestine - Helps in dilution, making liquid more dilute, reducing the concentration of chemical


Lungs and kidneys play important role in regulating blood pH.


Role of the kidney in Acid-Base Balance


Kidney has two very important roles in maintaining acid- base balance-


1. Secretes H+ ion into urine.

2. Reabsorb bicarbonate (HCO3) from urine back to the blood.

3. Kidney regulates pH by excretion acid, primarily in ammonium ion NH4.

By adjusting amounts reabsorbed and secreted, they balance bloodstream pH.



Role of Respiratory System in Acid-Base Balance - Blood pH Regulation


1. The lungs regulate pH through the retention or elimination of CO2 by changing rate and volume of ventilation.


2. When CO2 dissolved in blood, it increases acidic content of blood as a result of decrease pH value. Base buffers come into action by mixing with plasma of blood and then neutralized acidic content of blood.


Similarly when alkaline value of blood increase, Acidic buffer in blood plasma come into action.

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