Basics of Acid Base & Buffer Systems

Introduction to Acid-Base Balance

• Important for maintaining hydrogen ion concentration in body fluids.
• Balance achieved through:
  • Buffers in extracellular fluid.
  • Respiratory excretion of CO2.
  • Renal reabsorption of bicarbonate and secretion of hydrogen ions.

pH Review

• Definition: pH = - log [H+].
• Range: 0 to 14.
  • Acidic solution: pH < 7.
  • Basic solution: pH > 7.
• Acids: H+ donors.
• Bases: H+ acceptors or give up OH-.
• Effect on Enzymes and Hormones:
  • Enzymes have specific pH ranges for optimal function.
  • pH affects electrolyte balance and hormonal function.

Body pH Homeostasis

• Normal arterial blood pH: 7.35 - 7.45.
• Importance of maintaining pH:
  • Prevents enzyme denaturation.
  • Maintains synaptic function.
• Acidosis: pH < 7.35.
• Alkalosis: pH > 7.45.

Sources of Acid Threats

1. Food (fats and proteins).
2. Metabolism of lipids and proteins.
3. Cellular metabolism producing CO2.

Buffer Systems

• Chemical Buffer Systems: Convert strong acids/bases to weak ones.
  • Bicarbonate Buffer: Most abundant, acts extracellularly and intracellularly.
  • Phosphate Buffer: Major intracellular and renal buffer.
  • Protein Buffer: Includes hemoglobin and other proteins.

Physiological Buffer Systems

Respiratory Mechanism

• Adjusts body pH by altering CO2 exhalation.
• Hypoventilation: Retains CO2.
• Hyperventilation: Excretes excess CO2.

Renal Mechanism

• Can excrete excess base and eliminate large amounts of acid.
• Functions:
  • Reabsorption of filtered bicarbonate.
  • Generation of new bicarbonate.
  • Excretion of H+.
• Buffering in Tubules:
  • Ammonia and phosphate buffer systems stabilize pH in renal tubules.

Summary

• Chemical Buffers: First line of defense.
• Physiological Buffers: Second and third lines, including respiratory and renal adjustments.
• Kidney Function:
  • Filters and reabsorbs bicarbonate efficiently.
  • Secretes excess H+ using ammonia and phosphate buffers.

Important Notes

• Maintaining blood pH within a narrow range is critical for physiological functions.
• Body produces more acids than bases, requiring robust buffering and excretion systems.
• Renal and respiratory systems work together to maintain acid-base balance.

Questions & Key Points

1. Chemical Buffers: Bicarbonate, phosphate, and protein systems.
2. Kidney Functions: Bicarbonate reabsorption, H+ secretion, and new bicarbonate generation.
3. Importance of pH: Enzyme function and neural transmission depend on stable pH levels.
4. Acid Sources: Diet and cellular metabolism.
5. Buffer Efficacy: Ammonia is a key buffer in renal tubules, especially under acidic conditions.

These notes capture the essence of the presentation on acid-base balance and buffer systems, detailing the mechanisms and importance of maintaining pH within the normal range.