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Questions and Answers
What physiological role do the kidneys play in maintaining acid-base balance?
What physiological role do the kidneys play in maintaining acid-base balance?
Which statement correctly describes the relationship between pH and hydrogen ion concentration?
Which statement correctly describes the relationship between pH and hydrogen ion concentration?
What reaction describes the simplified relationship between carbon dioxide and bicarbonate in the body?
What reaction describes the simplified relationship between carbon dioxide and bicarbonate in the body?
What is the primary function of carbonic acid in the body?
What is the primary function of carbonic acid in the body?
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Which condition is defined by an increased concentration of hydrogen ions?
Which condition is defined by an increased concentration of hydrogen ions?
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What primarily distinguishes venous blood from arterial blood in terms of pH and hydrogen concentration?
What primarily distinguishes venous blood from arterial blood in terms of pH and hydrogen concentration?
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The law of mass action states that the velocity of a reaction is dependent on what factor?
The law of mass action states that the velocity of a reaction is dependent on what factor?
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What is the daily production range of non-carbonic acids generated from protein metabolism?
What is the daily production range of non-carbonic acids generated from protein metabolism?
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What is the minimum urine pH?
What is the minimum urine pH?
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What is the primary buffer in the tubular fluid for removing extra hydrogen?
What is the primary buffer in the tubular fluid for removing extra hydrogen?
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Where does the majority of monohydrogen phosphate buffering occur?
Where does the majority of monohydrogen phosphate buffering occur?
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Which of the following is NOT a cause of metabolic alkalosis?
Which of the following is NOT a cause of metabolic alkalosis?
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What is the role of Carbonic Anhydrase (CA) in bicarbonate reabsorption in the proximal tubule?
What is the role of Carbonic Anhydrase (CA) in bicarbonate reabsorption in the proximal tubule?
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Which of these mechanisms contribute to ammonia excretion in the collecting duct?
Which of these mechanisms contribute to ammonia excretion in the collecting duct?
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What happens to intracellular pH when potassium moves out of the cell?
What happens to intracellular pH when potassium moves out of the cell?
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How does aldosterone promote hydrogen loss in the collecting duct?
How does aldosterone promote hydrogen loss in the collecting duct?
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What is the role of the sodium-hydrogen exchanger in the thick ascending limb of the loop of Henle?
What is the role of the sodium-hydrogen exchanger in the thick ascending limb of the loop of Henle?
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A patient with diabetes mellitus who is experiencing uncontrolled blood sugar is likely to develop what condition?
A patient with diabetes mellitus who is experiencing uncontrolled blood sugar is likely to develop what condition?
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What is the role of glutamine in ammonia production?
What is the role of glutamine in ammonia production?
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Which of the following is a TRUE statement about intracellular acidosis?
Which of the following is a TRUE statement about intracellular acidosis?
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Which of these is a mechanism for increased acid excretion in the collecting duct?
Which of these is a mechanism for increased acid excretion in the collecting duct?
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What is the significance of the negative environment in the lumen of the collecting duct?
What is the significance of the negative environment in the lumen of the collecting duct?
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What is the consequence of renal failure on acid excretion?
What is the consequence of renal failure on acid excretion?
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Which of the following situations can lead to increased acid production in the body?
Which of the following situations can lead to increased acid production in the body?
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What happens to the kidneys' ability to excrete acid in renal failure?
What happens to the kidneys' ability to excrete acid in renal failure?
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How does hypokalemia influence bicarbonate reabsorption during metabolic alkalosis?
How does hypokalemia influence bicarbonate reabsorption during metabolic alkalosis?
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What effect does renal failure have on ammonium excretion over time?
What effect does renal failure have on ammonium excretion over time?
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Which statement correctly describes the long-term effect of bone buffering in renal failure?
Which statement correctly describes the long-term effect of bone buffering in renal failure?
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What is the primary cause of acidosis in patients with renal failure?
What is the primary cause of acidosis in patients with renal failure?
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What is the primary mechanism for the kidneys to retain bicarbonate?
What is the primary mechanism for the kidneys to retain bicarbonate?
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Which transporter is crucial for hydrogen ion secretion in the nephron?
Which transporter is crucial for hydrogen ion secretion in the nephron?
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What is a key factor that leads to metabolic alkalosis?
What is a key factor that leads to metabolic alkalosis?
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What primarily causes metabolic acidosis?
What primarily causes metabolic acidosis?
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Which of these factors does NOT contribute to acid-base balance in the nephron?
Which of these factors does NOT contribute to acid-base balance in the nephron?
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Which condition is primarily associated with an increase in plasma bicarbonate concentration?
Which condition is primarily associated with an increase in plasma bicarbonate concentration?
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What effect does increased hydrogen ion concentration have on blood pH?
What effect does increased hydrogen ion concentration have on blood pH?
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Which of the following is a consequence of excessive vomiting on acid-base balance?
Which of the following is a consequence of excessive vomiting on acid-base balance?
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Study Notes
Acid-Base Physiology Regulation
- Plasma hydrogen concentration is tightly controlled, far lower than common electrolytes.
- Hydrogen ions react with proteins; changes impact physiological functions.
- Acid-base balance measured by arterial plasma hydrogen concentration (pH).
- Lower pH means more acidity and hydrogen ions.
- Acids donate hydrogen ions, bases accept them.
- Primary renal mechanism for retaining bicarbonate and excreting hydrogen: reabsorbing bicarbonate in the proximal tubule and secreting hydrogen via the distal tubule and collecting ducts.
Classes of Acids
- Two main acid types: carbonic acid (H2CO3) and non-carbonic acids.
- Carbonic acid forms from CO2 and water, with high daily production (15,000 millimoles). CO2 removed by respiration.
- Non-carbonic acids from protein metabolism (~50-100 milliequivalents daily).
- The body manages acid concentration by combining acids with buffers.
Buffer Systems and Reactions
- Major buffer system: CO2/bicarbonate (CO2 + H2O HCO3− + H+).
- Increased hydrogen concentration shifts this reaction to form more CO2 and water.
- Venous blood has lower pH and increased hydrogen compared to arterial blood.
- Survival pH range: 6.8 to 7.8 (hydrogen concentration: 16 to 120 nanoequivalents/liter).
Acidemia and Alkalemia
- Acidemia: increased hydrogen concentration, lowered pH.
- Alkalemia: decreased hydrogen concentration, elevated pH.
- Acidosis: process decreasing pH; alkalosis increases pH.
- Net hydrogen loss leads to alkalosis (pH > 7.4); net gain causes acidosis (pH < 7.4).
- Decreased bicarbonate relates to increased hydrogen and acidosis.
- Increased bicarbonate relates to decreased hydrogen and alkalosis.
Acid-Base Regulation by Kidneys
- Kidneys excrete daily 50-100 milliequivalents hydrogen.
- Hydrogen excretion via renal tubules (proximal, loop of Henle, collecting ducts).
- Minimum urine pH: 4.5 (much more acidic than plasma).
- Hydrogen buffered in tubular lumen by monohydrogen phosphate and ammonia.
Bicarbonate Reabsorption
- Filtered bicarbonate must be reabsorbed.
- Proximal tubule major site for bicarbonate reabsorption (80-90%).
- Hydrogen combines with bicarbonate forming H2CO3 using carbonic anhydrase (CA).
- CA catalyzes the conversion back to bicarbonate and hydrogen intracellularly.
- Bicarbonate leaves cell via sodium bicarbonate transporter.
- Loop of Henle (thin ascending limb) also reabsorbs some bicarbonate (about 15%).
Acid Load Excretion
- Monohydrogen phosphate is a key tubular fluid buffer, combining with hydrogen to form dihydrogen phosphate, excreted in urine.
- Major monohydrogen phosphate buffering happens in the collecting duct.
- Ammonia excretion is major adaptation to acid loading, from 40 to 300 milliequivalents/day.
- Ammonia production from glutamine metabolism; crucial in proximal tubules.
- Ammonium excretion via two methods: proximal tubule (mimicking hydrogen secretion) and collecting duct (diffusion and reaction with hydrogen).
Collecting Duct Activity
- Hydrogen ATPase excretes hydrogen; combines with monohydrogen phosphate for excretion.
- Potassium reabsorbed with hydrogen excretion.
- Ammonia diffuses, combines with hydrogen, forming ammonium and excreted.
Metabolic Alkalosis
- Primary elevation in plasma bicarbonate and increased extracellular pH.
- Common causes:
- Hydrogen loss (vomiting, nasogastric suction, diuretic use).
- Hyperaldosteronism: hypokalemia contributes to alkalosis.
- Volume depletion contributing to hyperaldosterone.
- Hypokalemia promotes bicarbonate reabsorption and inhibits excretion; hypokalemia promotes cellular acidosis, which enhances bicarbonate reabsorption.
- Intracellular acidosis facilitates bicarbonate reabsorption.
- Cortical collecting duct (type A intercalated cells) generate bicarbonate to combat alkalosis.
- Aldosterone increases sodium channels and hydrogen ATPase activity, promoting hydrogen loss.
Metabolic Acidosis
- Reduced plasma bicarbonate concentration.
- Common causes:
- Increased acid production (lactic acidosis, ketoacidosis, ingestion of acids).
- Loss of bicarbonate (diarrhea, renal tubular failure).
- Renal failure limits acid excretion, affecting ammonium and bicarbonate balance.
- Initial increased ammonium excretion then decreases over time.
- Excess acid buffering by bicarbonate, cells, and bone; can lead to bone loss.
- Renal failure can damage the nephron from increased ammonium production.
- Sodium-hydrogen exchanger (NHE); Hydrogen ATPase; Sodium-bicarbonate co-transporter are directly involved in acid-base balance. Sodium-potassium pump is not directly involved.
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Description
Test your knowledge on the regulation of acid-base physiology, including the mechanisms of hydrogen ion control and the classes of acids. Explore buffer systems and their reactions, as well as the implications of pH levels in physiological functions. Perfect for students studying advanced biology or physiology.
