HLTH1004 W2 L.2.4.3

Acid-Base Balance

• Maintaining acid-base balance is crucial for health.

• Disruptions can lead to imbalances:

  • Too much hydrogen ions results in acidosis (blood pH less than 7.35).

  • Too few hydrogen ions results in alkalosis (blood pH greater than 7.45).

• The normal pH range is narrow; balance must be maintained for organ function.

Sources of Acids in the Body

• The body contains different types of acids:

  • Fixed Acids:

    • Remain in body fluids; eliminated by kidneys.

    • Examples: sulfuric and phosphoric acids.

    • Produced during the breakdown of amino acids, phospholipids, and nucleic acids.

  • Metabolic Acids:

    • Derived from metabolism (e.g., lactic acid, pyruvic acid, ketone bodies).

    • Generally broken down easily and do not accumulate significantly.

  • Volatile Acids:

    • Can convert to gas and leave the body.

    • Example: carbonic acid formed from water and carbon dioxide.

    • Breaks down into carbon dioxide and water, with CO₂ diffusing through blood and exhaled.

Role of Carbonic Anhydrase

• Carbonic anhydrase is a key enzyme for converting carbon dioxide and water into carbonic acid and vice versa.

• Found in numerous body cells, including:

  • Red blood cells

  • Liver and kidney cells

  • Stomach lining

• Detects carbon dioxide levels, which are critical for regulating blood acidity (pH).

Impact of Carbon Dioxide on pH

• Increased CO₂ leads to higher concentrations of hydrogen ions, lowering blood pH (making it more acidic).

• At alveoli, CO₂ diffuses into atmosphere causing H⁺ and HCO^- in alveolar capillaries to decrease (blood pH rises)

• A trigger mechanism is in place to prevent toxic carbon dioxide buildup:

  • Binds to hemoglobin, reducing oxygen transport.

• Maintaining CO₂ balance is vital; excess leads to health issues.

Mechanisms for Acid-Base Balance

• The body employs multiple mechanisms to control hydrogen ion concentrations:

  • Gains of Hydrogen Ions:

    • Sources include food intake, metabolic activity, and breakdown products.

  • Losses of Hydrogen Ions:

    • Eliminated primarily through the kidneys and lungs.

• Neutralization of excess hydrogen ions is crucial to prevent tissue damage.

• Buffers in body fluids, such as blood, temporarily neutralize acids and maintain pH stability.

Acids and Bases Classifications

• Acids and bases can be classified into:

  • Strong Acids and Bases:

    • Completely dissociate in solution; e.g., hydrochloric acid (HCl).

  • Weak Acids and Bases:

    • Partially dissociate; fewer hydrogen ions present resulting in higher pH.

• Example: Carbonic acid acts as a weak acid in body fluids.

Carbonic Acid Equilibrium

• Carbonic acid exists in equilibrium with its dissociation products (hydrogen ions and bicarbonate ions).

• H₂CO₃ ←→ H⁺ + HCO^-

• The equation shows the balance between carbonic acid and hydrogen ions:

  • When hydrogen is released, pH decreases (more acidic), and when it is absorbed, pH increases (more alkaline).

• This equilibrium is vital for maintaining acid-base homeostasis within the body.