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Questions and Answers
What is the primary cause of hypoxemia related to diffusion abnormalities in the alveolar-capillary bed?
What is the primary cause of hypoxemia related to diffusion abnormalities in the alveolar-capillary bed?
What would happen if the pH of a strong acid is raised above its pK value?
What would happen if the pH of a strong acid is raised above its pK value?
Which of the following buffers is most important in the plasma for maintaining acid-base balance?
Which of the following buffers is most important in the plasma for maintaining acid-base balance?
Which of the following describes the relationship between pH and H concentration?
Which of the following describes the relationship between pH and H concentration?
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What is the typical reference range for the anion gap in blood plasma?
What is the typical reference range for the anion gap in blood plasma?
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What does a pH level below 7.34 indicate?
What does a pH level below 7.34 indicate?
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Which condition is NOT associated with an increased anion gap?
Which condition is NOT associated with an increased anion gap?
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What should be done cautiously when using O2 concentrations of 60% or higher?
What should be done cautiously when using O2 concentrations of 60% or higher?
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Which component of the blood plays a major role in maintaining pH homeostasis?
Which component of the blood plays a major role in maintaining pH homeostasis?
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What is indicated by a pH of 7.40 in arterial blood?
What is indicated by a pH of 7.40 in arterial blood?
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How much 0.05 mol/L HCl is needed to change 100 mL of normal blood from a pH of 7.35 to a pH of 7.00?
How much 0.05 mol/L HCl is needed to change 100 mL of normal blood from a pH of 7.35 to a pH of 7.00?
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What can a deviation of H concentration from its normal range result in?
What can a deviation of H concentration from its normal range result in?
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What happens to CO2 when the lungs fail to remove it at the rate of its production?
What happens to CO2 when the lungs fail to remove it at the rate of its production?
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Which substance is primarily responsible for binding H in the kidneys?
Which substance is primarily responsible for binding H in the kidneys?
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What role do the lungs primarily play in acid-base homeostasis?
What role do the lungs primarily play in acid-base homeostasis?
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How does the kidney respond under alkalotic conditions?
How does the kidney respond under alkalotic conditions?
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What is the daily net excess of acid that the body must excrete through the kidneys under normal conditions?
What is the daily net excess of acid that the body must excrete through the kidneys under normal conditions?
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What is the consequence of kidney failure concerning HCO3 levels in plasma?
What is the consequence of kidney failure concerning HCO3 levels in plasma?
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What is the role of hemoglobin in the transport of oxygen?
What is the role of hemoglobin in the transport of oxygen?
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What occurs when the rate of CO2 removal is faster than its production?
What occurs when the rate of CO2 removal is faster than its production?
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What is formed when HCO3 combines with H in the kidney's tubular cell?
What is formed when HCO3 combines with H in the kidney's tubular cell?
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What is the minimum urine pH that the kidney can excrete?
What is the minimum urine pH that the kidney can excrete?
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What is the primary role of the bicarbonate-carbonic acid buffering system?
What is the primary role of the bicarbonate-carbonic acid buffering system?
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Which factor does NOT play a role in the regulation of blood pH?
Which factor does NOT play a role in the regulation of blood pH?
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How does the addition of an acid like HCl affect the bicarbonate-carbonic acid system?
How does the addition of an acid like HCl affect the bicarbonate-carbonic acid system?
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What equation depicts the relationship between lung and kidney functions in maintaining pH?
What equation depicts the relationship between lung and kidney functions in maintaining pH?
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Which buffer system is specifically involved in the plasma and red blood cells?
Which buffer system is specifically involved in the plasma and red blood cells?
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How do kidneys contribute to the regulation of blood pH?
How do kidneys contribute to the regulation of blood pH?
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What role does H2CO3 play in the bicarbonate-carbonic acid system upon formation?
What role does H2CO3 play in the bicarbonate-carbonic acid system upon formation?
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What characterizes the buffering capacity of hemoglobin?
What characterizes the buffering capacity of hemoglobin?
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What happens to carbon dioxide during a metabolic process within tissues?
What happens to carbon dioxide during a metabolic process within tissues?
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What can cause an increase in HCO3 levels besides the infusion of lactate?
What can cause an increase in HCO3 levels besides the infusion of lactate?
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What is the expected effect of most diuretics on HCO3 levels?
What is the expected effect of most diuretics on HCO3 levels?
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How is the Henderson-Hasselbalch equation related to acid-base homeostasis?
How is the Henderson-Hasselbalch equation related to acid-base homeostasis?
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Which condition is least likely to impair HCO3 reabsorption?
Which condition is least likely to impair HCO3 reabsorption?
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What role does the destruction of alveoli play in gas exchange?
What role does the destruction of alveoli play in gas exchange?
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What effect does pulmonary edema have on the diffusion of gases?
What effect does pulmonary edema have on the diffusion of gases?
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What is a potential cause of airway blockage that impacts gas exchange?
What is a potential cause of airway blockage that impacts gas exchange?
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What occurs when there is an inadequate blood supply to the lungs?
What occurs when there is an inadequate blood supply to the lungs?
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In terms of buffering capacity, what is pK in the Henderson-Hasselbalch equation?
In terms of buffering capacity, what is pK in the Henderson-Hasselbalch equation?
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Which of the following factors does NOT influence O2 diffusion through the alveoli?
Which of the following factors does NOT influence O2 diffusion through the alveoli?
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Study Notes
Acid-Base Balance
- An acid is a substance that releases hydrogen (H+) or hydronium ions (H3O+) in water.
- A base is a substance that releases hydroxyl ions (OH-) in water.
- The relative strengths of acids and bases, and their ability to dissociate in water, are described by their dissociation constant (ionization constant K value).
- A pK value, which is the negative log of the ionization constant, indicates the pH at which protonated and unprotonated forms are equally concentrated.
- Strong acids have pK values less than 3, and strong bases have pK values greater than 9.
- Increasing the pH above the pK of an acid causes it to dissociate and release H+.
- Lowering the pH below the pK of a base causes it to release OH-.
- Many substances have multiple pK values, meaning they can accept or donate more than one hydrogen ion.
- Blood pH is maintained at 7.35-7.45.
- Changing blood pH by 0.3 requires a significant amount of acid or base.
- Normal serum H+ concentration is 36-44 nmol/L(pH 7.34-7.44). However, metabolism produces greater quantities of H+.
- Lungs and kidneys help maintain pH homeostasis.
- Alterations in H+ levels outside the normal range disrupt metabolic processes and can cause serious consequences, including death.
- The logarithmic pH scale expresses hydrogen ion concentration (c is concentration): pH = log1/cH = -log cH.
- Arterial blood pH is 7.40, equivalent to an H+ concentration of 40 nmol/L.
Buffer Systems
- The bicarbonate-carbonic acid system is a weak acid system that buffers blood. It combines with excess acids or bases to minimize pH changes. H2CO3 is a weak acid, not completely dissociating.
- In the presence of an acid, bicarbonate (HCO3-) combines with the H+ to form carbonic acid (H2CO3).
- In the presence of a base, carbonic acid (H2CO3) combines with the OH- to form more bicarbonate (HCO3-) and water (H2O).
- Phosphate buffer system (HPO4 2- / H2PO4-) plays a role in plasma and red blood cells, and is involved in the exchange of sodium ion in the urine filtrate.
- Plasma proteins, especially imidazole groups of histidine, form an important buffer system in plasma.
Kidney and Lung Function in Acid-Base Balance
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The lungs regulate pH by controlling CO2 levels.
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The kidneys regulate pH by excreting acids (primarily ammonium ion) and reclaiming bicarbonate.
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In normal conditions, the body produces 50-100 mmol/L acid that must be excreted by the kidneys.
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Urine pH is approximately 4.5, so non-buffered H+ is excreted combined with dibasic phosphate, (HPO4-), and ammonia (NH3) as dihydrogen phosphate (H2PO4-) and ammonium (NH4+).
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Plasma HCO3- level rarely exceeds 30 mmol/L unless excretory capabilities are compromised.
Anion Gap
- The anion gap is a calculation of the difference between anions and cations in the blood.
- It helps estimate acid-base and electrolyte disturbances.
- Formula: Anion Gap (AG)=([Na+]+[K+])-([HCO3-]+[Cl-])
- Reference range is 10 to 20 mmol/L.
Other Important Details
- pCO2 (partial pressure of carbon dioxide) is a key factor in regulating acid-base balance.
- The most important buffers are bicarbonate/carbonic acid, phosphate, and plasma proteins, including histidine, hemoglobin.
- Factors influencing O2 movement include alveolar surface area, pulmonary edema (fluid leaking), and airway blockage.
- Inadequate blood supply to the lungs impedes O2 exchange, while increased CO2 removal can decrease [H+] in the blood.
- The lungs provide initial defense against changes in blood pH within seconds.
- The kidneys have a key role in maintaining acid-base homeostasis by controlling H+ and HCO3-.
- Different causes of acidosis and alkalosis affect acid-base balance, including metabolic and respiratory factors.
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Description
Test your knowledge on acid-base balance concepts, including the definitions and roles of acids and bases, dissociation constants, and pK values. Understand how these factors contribute to maintaining blood pH and the implications of pH changes.
