Explain the main buffer systems in the human body, including their pK, concentration, compartment, and relevant organs.

This table summarizes the main buffer systems in the human body, which are crucial for maintaining a stable pH. Let's break down each column and the buffer systems:

• Buffer System: This column lists the specific chemical pairs that act as buffers (a weak acid and its conjugate base).
• pK: This is the negative logarithm of the acid dissociation constant ($K_a$). It indicates the pH at which the buffer system is most effective (where the concentrations of the weak acid and its conjugate base are equal).
• Concentration: This shows the typical concentration of the buffer components in the body.
• Compartment: This indicates where the buffer system primarily operates:
  • ICF (Intracellular Fluid): Fluid inside cells.
  • ECF (Extracellular Fluid): Fluid outside cells, including plasma and interstitial fluid.
• Organ/s: This specifies the main locations or organs where the buffer system is particularly important.

Here's an explanation of each buffer system listed:

1. Bicarbonate (H₂CO₃/HCO₃⁻):

   • pK 6.1: This system is vital in both ICF and ECF, especially in blood and plasma. It's closely linked to the respiratory system (CO₂) and kidneys (bicarbonate regulation), making it highly adaptable.

2. Haemoglobin (HHb/Hb⁻):

   • pK 7.3: Found within the ICF of red blood cells in the blood. Hemoglobin buffers H⁺ ions generated from CO₂ transport, playing a key role in maintaining blood pH.

3. Phosphate (H₂PO₄⁻/HPO₄²⁻):

   • pK 6.8: Important in both ICF (especially in red blood cells) and ECF, and significantly in the urinary system. It helps buffer the pH of urine and intracellular fluid.

4. Protein (HPr/Pr⁻):

   • Proteins have many ionizable groups, allowing them to buffer H⁺ ions. They are abundant in both ICF and ECF (blood and plasma), making them a powerful and versatile buffer system.

5. Ammonia (NH₃/NH₄⁺):

   • pK 9.8: Primarily functions in the ECF within the urinary system. The kidneys use ammonia to excrete excess acid, forming ammonium ions (NH₄⁺) that are then eliminated in urine.