Acid-Base Balance Quiz
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Questions and Answers

What is the primary function of buffers in acid-base physiology?

  • To enhance the production of acids in the body
  • To eliminate CO2 from the system
  • To increase H+ concentration in the body fluids
  • To regulate H+ concentrations in the extracellular fluid (correct)
  • Which buffer system provides the largest proportion of buffer capacity in the body?

  • Phosphate buffer system
  • Ammonium buffer system
  • Protein buffer system
  • Bicarbonate buffer system (correct)
  • Which of the following is NOT a type of acid produced in the body?

  • Volatile acid
  • Hydrochloric acid (correct)
  • Non-volatile acid
  • Carbonic acid
  • How does renal compensation primarily affect the extracellular fluid?

    <p>By altering bicarbonate (HCO3-) levels</p> Signup and view all the answers

    What role do ammonia (NH3) and ammonium (NH4+) ions play in the body?

    <p>They contribute to the generation of bicarbonate in the kidneys</p> Signup and view all the answers

    What component of a buffer system is present in greater concentration at low pH levels?

    <p>Weak acid</p> Signup and view all the answers

    Which buffer system is primarily responsible for maintaining pH in the extracellular fluid?

    <p>Bicarbonate buffer system</p> Signup and view all the answers

    Under what condition can the weak acid (HA) contribute H+ ions in a buffer system?

    <p>Base load</p> Signup and view all the answers

    What is the primary role of hemoglobin in blood buffering?

    <p>Buffering through imidazole groups</p> Signup and view all the answers

    Why is the phosphate buffer system considered unimportant in blood?

    <p>It has low concentrations in blood</p> Signup and view all the answers

    What occurs to [H+] when pH increases from 7.4 to 7.6?

    <p>[H+] decreases by 15 nEq/L</p> Signup and view all the answers

    What is the effect on [H+] when pH decreases from 7.4 to 7.2?

    <p>[H+] increases by 23 nEq/L</p> Signup and view all the answers

    Which statement about changes in pH is correct?

    <p>A given change in pH in the acidic range reflects a larger change in [H+].</p> Signup and view all the answers

    Which of the following pH values corresponds to extreme acidosis?

    <p>7.0</p> Signup and view all the answers

    What is a characteristic of volatile acids in the body?

    <p>They are produced from aerobic metabolism of cells.</p> Signup and view all the answers

    Which acid is considered a non-volatile acid produced from protein catabolism?

    <p>Sulfuric acid</p> Signup and view all the answers

    What pH level indicates maximum urine acidity?

    <p>4.5</p> Signup and view all the answers

    Which of the following is associated with diabetic ketosis?

    <p>β-hydroxy butyric acid</p> Signup and view all the answers

    What is the primary role of the kidneys in acid-base balance?

    <p>Synthesis of new bicarbonate when plasma bicarbonate is low</p> Signup and view all the answers

    How do buffers respond to acid-base disturbances?

    <p>They minimize pH changes</p> Signup and view all the answers

    Which factor is the primary regulator of ventilation and acid-base balance?

    <p>PaCO2 levels</p> Signup and view all the answers

    What happens to bicarbonate when plasma levels exceed 26 mEq/L?

    <p>It appears in urine as it is excreted</p> Signup and view all the answers

    What does decreased bicarbonate or increased PCO2 indicate?

    <p>Acidosis</p> Signup and view all the answers

    How do both PCO2 and bicarbonate levels contribute to pH maintenance?

    <p>They can vary independently while maintaining pH</p> Signup and view all the answers

    What is the effect of hyperventilation on acid-base balance?

    <p>It results in respiratory alkalosis</p> Signup and view all the answers

    What occurs to filtered bicarbonate when plasma bicarbonate is low?

    <p>It undergoes complete recovery</p> Signup and view all the answers

    What is a common cause of metabolic alkalosis?

    <p>Alkaline antacid ingestion</p> Signup and view all the answers

    What happens to pH during respiratory alkalosis?

    <p>It increases above 7.45</p> Signup and view all the answers

    Which statement about renal compensation in respiratory alkalosis is accurate?

    <p>It conserves H+ ions</p> Signup and view all the answers

    What primary condition leads to respiratory acidosis?

    <p>Decreased ventilation</p> Signup and view all the answers

    Which of the following is involved in metabolic alkalosis correction?

    <p>HCO3- excretion by kidneys</p> Signup and view all the answers

    What physiological change mainly characterizes respiratory compensation for metabolic alkalosis?

    <p>Hypoventilation</p> Signup and view all the answers

    In respiratory alkalosis caused by hyperventilation, what happens to HCO3- levels?

    <p>They decrease as a result of renal excretion</p> Signup and view all the answers

    What is a common feature of metabolic alkalosis?

    <p>Decreased stomach HCl secretion</p> Signup and view all the answers

    Study Notes

    Acid-Base Balance

    • Acid-base physiology is the study of H+ concentration ([H+]) regulation in the extracellular fluid (ECF).
    • [H+] is tightly regulated through powerful homeostatic mechanisms: buffers, respiratory compensation, and renal compensation.
    • The bicarbonate buffer system is considered the most important buffer due to its high concentration and the tight regulation of both CO2 and HCO3- by the lungs and kidneys.
    • Buffer effectiveness depends on its concentration and pK (dissociation constant).
    • Buffers are weak acids and their conjugate bases. At low pH, weak acid [HA] dominates, and at high pH, conjugate base [A-] dominates.
    • Buffers prevent drastic pH changes by absorbing or releasing H+ ions as needed.

    Buffer Systems in the Body

    • The major buffers in the body include:
      • Bicarbonate: Primary buffer in the ECF, comprising 53% of total buffering. It has a low pK (6.1) but its high concentration and the regulation of both H2CO3/CO2 and HCO3- make it very effective.
      • Hemoglobin: Second most important buffer, accounting for 35% of total ECF buffering. Imidazole groups on histidine and α-amino groups act as primary buffer sites on proteins.
      • Proteins: Contribute 7% of total ECF buffering. They have good pK values (6.4-7.9) but their concentrations are too low.
      • Phosphate: Less significant in blood due to low concentration, it's more important in urine where its concentration is higher.

    Measuring Acid-Base Status: pH & H+ concentration

    • pH is a logarithmic measure of H+ concentration. A change of 0.2 pH units represents a significant change in [H+].
    • Normal pH in plasma is 7.4, corresponding to an [H+] of 0.00004 mEq/L.
    • Acidosis: pH below 7.35, reflecting increased [H+].
    • Alkalosis: pH above 7.45, reflecting decreased [H+].
    • Different body fluids have varying pH and H+ concentrations.

    Sources of H+ in the Body

    • Volatile acid: Primarily CO2, produced by aerobic metabolism of cells and eliminated by the lungs.
    • Non-volatile or fixed acids: Examples include sulfuric acid from protein catabolism, phosphoric acid from phospholipid catabolism, and lactic acid from exercise.
    • Other acid loads: Result from diabetic ketoacidosis, poisoning ingestion, etc.

    Acid-Base Disorders

    • Metabolic acidosis: Decreased [HCO3-] or increased non-volatile acid load, resulting in decreased pH (less than 7.35).
    • Metabolic alkalosis: Increased [HCO3-] or loss of H+, leading to increased pH (greater than 7.45).
    • Respiratory acidosis Increased PCO2 (CO2 retention), resulting in decreased pH (less than 7.35).
    • Respiratory alkalosis: Decreased PCO2 (CO2 loss), leading to increased pH (greater than 7.45).

    Compensation Mechanisms

    • Buffers: Rapidly minimize pH changes but cannot restore pH to normal.
    • Respiratory compensation: Lungs regulate CO2 levels by altering ventilation rate.
    • Renal compensation: Kidneys regulate HCO3- levels through reabsorption, secretion, and new synthesis.

    Respiratory Control of CO2

    • Lungs primarily regulate ventilation rate based on PCO2 levels.
    • Hyperventilation lowers PaCO2, resulting in alkalosis.
    • Hypoventilation raises PaCO2, resulting in acidosis.

    Renal Control of Bicarbonate

    • Kidneys maintain plasma [HCO3-] within a narrow range (22-26 mEq/L).
    • HCO3- recovery: Kidneys recover filtered HCO3- when plasma [HCO3-] is below 26 mEq/L.
    • HCO3- synthesis: Kidneys synthesize “new” HCO3- when plasma [HCO3-] is above 26 mEq/L.
    • HCO3- excretion: Kidneys excrete excess HCO3- in urine.

    Mechanisms of Renal Bicarbonate Recovery

    • The process is driven by H+ secretion.
    • H+ is formed in the intracellular fluid by the reaction of CO2 and water catalyzed by carbonic anhydrase.
    • H+ is exchanged for Na+ (primarily in the proximal tubule) or actively secreted (in the distal tubule).
    • HCO3- enters the peritubular capillary blood.

    Titratable Acidity & Ammonia (NH3) & Ammonium (NH4+) Ions

    • Titratable acidity: Refers to the acid excreted in the urine that can be titrated with a base.
    • Ammonia (NH3) and ammonium (NH4+) ions: NH3 is produced by renal cells and combines with H+ to form NH4+, which is excreted in the urine. This process is critical for generating new HCO3- and removing excess acid from the body.

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    Description

    Test your understanding of acid-base physiology and the mechanisms that regulate hydrogen ion concentration in the body. This quiz covers buffer systems, especially the bicarbonate buffer system, and their importance in maintaining pH balance. Challenge yourself with questions on homeostatic mechanisms, buffer effectiveness, and the major buffers in the body.

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