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Questions and Answers
What process allows for the exchange of sodium with hydrogen ions in the kidneys during acidosis?
What process allows for the exchange of sodium with hydrogen ions in the kidneys during acidosis?
Which enzyme is responsible for producing ammonia from glutamine in renal tubular cells?
Which enzyme is responsible for producing ammonia from glutamine in renal tubular cells?
In the proximal convoluted tubules, what percentage of filtered bicarbonate is normally reclaimed?
In the proximal convoluted tubules, what percentage of filtered bicarbonate is normally reclaimed?
What is the important buffer system of extracellular fluid?
What is the important buffer system of extracellular fluid?
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What happens to ammonium ions once ammonia forms in the renal tubular cells?
What happens to ammonium ions once ammonia forms in the renal tubular cells?
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What is acidosis defined as in terms of blood pH?
What is acidosis defined as in terms of blood pH?
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Which condition is a cause of respiratory acidosis?
Which condition is a cause of respiratory acidosis?
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Which of the following is a characteristic of metabolic acidosis?
Which of the following is a characteristic of metabolic acidosis?
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What primarily enables the body to maintain compatible pH levels?
What primarily enables the body to maintain compatible pH levels?
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What leads to respiratory alkalosis?
What leads to respiratory alkalosis?
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How do buffers work to maintain pH?
How do buffers work to maintain pH?
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Which of the following combinations can be a buffer solution?
Which of the following combinations can be a buffer solution?
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What does an increase in HCO3- typically indicate?
What does an increase in HCO3- typically indicate?
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Which buffer system is primarily involved in the extracellular fluid (ECF)?
Which buffer system is primarily involved in the extracellular fluid (ECF)?
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What is the role of the basic part of a buffer when a strong acid is added?
What is the role of the basic part of a buffer when a strong acid is added?
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What occurs when water dissociates?
What occurs when water dissociates?
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Which of the following components is NOT part of the phosphate buffer system?
Which of the following components is NOT part of the phosphate buffer system?
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How do kidneys primarily adjust for acidosis?
How do kidneys primarily adjust for acidosis?
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Which statement accurately describes the role of water in the body?
Which statement accurately describes the role of water in the body?
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What is the importance of maintaining a pH of around 7.3-7.4 in human blood?
What is the importance of maintaining a pH of around 7.3-7.4 in human blood?
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Which mechanism is responsible for respiratory acidosis?
Which mechanism is responsible for respiratory acidosis?
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Which of the following conditions occurs when blood pH falls below 7.3?
Which of the following conditions occurs when blood pH falls below 7.3?
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What is produced in the kidneys in response to acidosis that aids in pH regulation?
What is produced in the kidneys in response to acidosis that aids in pH regulation?
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During respiratory alkalosis, what is the primary change that occurs in the body?
During respiratory alkalosis, what is the primary change that occurs in the body?
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How does the body maintain acid-base balance?
How does the body maintain acid-base balance?
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What is the normal pH range of human blood?
What is the normal pH range of human blood?
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Which two components make up the carboxylic acid/bicarbonate buffer system?
Which two components make up the carboxylic acid/bicarbonate buffer system?
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What is the correct relationship between hydrogen ion concentration and pH?
What is the correct relationship between hydrogen ion concentration and pH?
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What is the normal ratio of sodium bicarbonate to carbonic acid in the acid-base balance system?
What is the normal ratio of sodium bicarbonate to carbonic acid in the acid-base balance system?
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What is the normal daily water allowance for a healthy adult weighing 60 Kg?
What is the normal daily water allowance for a healthy adult weighing 60 Kg?
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Which process involves the use of water to break larger molecules into smaller units?
Which process involves the use of water to break larger molecules into smaller units?
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Which hormone is primarily involved in the regulation of water balance in the body?
Which hormone is primarily involved in the regulation of water balance in the body?
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What type of solution is characterized by solute particle sizes less than 1 nm?
What type of solution is characterized by solute particle sizes less than 1 nm?
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Which of the following best describes the pH of water?
Which of the following best describes the pH of water?
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What is a significant role of water in physiological processes?
What is a significant role of water in physiological processes?
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What is the role of water in dehydration reactions?
What is the role of water in dehydration reactions?
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Which concept is closely related to the regulation of blood pH?
Which concept is closely related to the regulation of blood pH?
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Study Notes
Water Metabolism
- Water is the predominant chemical component of living organisms.
- Daily normal allowance for an adult (60kg) is approximately 1800-2500ml/day.
- Water is a neutral substance with a pH of 7.
Regulation of Water Balance
- Water balance is regulated by:
- Hypothalamic mechanisms controlling thirst.
- Antidiuretic hormone (ADH).
- Retention or excretion of water by the kidneys.
Functions of Water
- Essential constituent of living cells. No living cell can resist drying.
- Solvent action forms a great number of crystalline and colloidal solutions.
- Serves as a universal medium for intracellular and extracellular chemical reactions.
- Plays a role in maintaining intracellular and extracellular pH.
- Important for absorption of food material from the intestine, reabsorption from kidney tubules, transport of food stuffs, manufacturing of secretions.
- Regulates body temperature.
- Acts as a lubricant preventing friction and drying.
- Mechanical buffer preventing injury to the nervous system.
pH
- pH is the negative logarithm of the hydrogen ion concentration (pH = -log [H+]).
- The square brackets around the H+ mean "concentration".
- pH symbol: p = power, H = Hydrogen.
- Water is a neutral solution because ionization gives equal amounts of H+ and OH- ions (10−7 = 7).
- Low pH values correspond to high concentrations of H+ ions.
- High pH values correspond to low concentrations of H+ ions.
pH Scale
- The pH scale ranges from 1 to 14.
- Values below 7 are acidic, values above 7 are alkaline.
- pH 7 is neutral.
Clinical Importance of pH
- Normal human blood pH is approximately 7.3-7.4.
- Blood pH below 7.3 is acidosis.
- Blood pH above 7.4 is alkalosis.
- Both acidosis and alkalosis are fatal conditions as changes affect enzyme activity (each enzyme has an optimal pH).
Acid-Base Balance
- Acid-base balance is vital for controlling hydrogen ion (H+) balance.
- Healthy kidneys and lungs control acid-base balance
- Normal ratio of Na bicarbonate (NaHCO3) to carbonic acid (H2CO3) is 20:1.
- Alterations in the concentration of one component are immediately compensated to maintain the ratio.
- Significant alterations result in acidosis or alkalosis.
- Body cells can only function within a narrow range of pH.
Clinical Abnormalities of Blood pH
-
Acidosis (below 7.3):
- Respiratory acidosis: Caused by CO2 buildup due to lung issues, respiratory depression, or breathing air with excess CO2.
- Metabolic acidosis: Caused by reduced bicarbonate level (e.g., severe muscle exercise, ketoacidosis in uncontrolled diabetes, increase of proteins in diet, failure of kidney to excrete acids, vomiting with significant loss of alkaline intestinal and pancreatic juices).
-
Alkalosis (above 7.4):
- Respiratory alkalosis: Caused by hyperventilation (e.g., high altitude, high fever).
- Metabolic alkalosis: Caused by excessive vomiting with HCl loss, and diets high in salt content.
Regulation of Blood pH
- Systems responsible for regulating blood pH include:
- Buffers
- Kidneys
- Respiratory system
Buffers
- Normal metabolism produces CO2, metabolic acids (e.g., lactic acid, ketone bodies), and inorganic acids (e.g., sulfuric acid).
- CO2 is a major source of acid reacting with water to produce carbonic acid.
- Buffers are crucial to maintain a pH compatible with life.
- Buffers work by substituting strong acids/bases with weaker ones, reducing free H+ and minimizing pH changes.
- Solutions resist pH changes when acids or alkalis are added moderately.
Types of Buffers
- Mixture of weak acid and its salt with strong base (e.g., carbonic acid and its salt, sodium bicarbonate, and acetic acid and sodium acetate).
- Mixture of weak base and its salt with strong acid (e.g., ammonium hydroxide and its salt, ammonium chloride).
Examples of Buffer Systems
- Carbonic acid/Bicarbonate buffer system: Found mainly in extracellular fluid.
- Phosphate buffer system: Found in intracellular fluids and RBCs.
- Protein buffers: Include amino acid buffers, hemoglobin and oxyhemoglobin in RBCs, and plasma protein buffers.
Mechanism of Buffer Action
- Any buffer consists of basic and acidic parts.
- Strong acid reacts with the basic part of the buffer, minimizing pH change.
- Strong base reacts with the acidic part of the buffer, minimizing pH change.
Renal Regulation of pH
- Kidneys regulate pH and acid-base balance through excretion of excess acids or bases.
- Mechanisms include:
- Excretion of hydrogen (H+) and potassium ions in tubules (acidifying the urine) responding to acidosis.
- Reabsorption of bicarbonate (HCO3−) responding to acidosis, and excreting it in response to alkalosis.
- Production and excretion of ammonia and ammonium ions (NH4+).
Excretion of Hydrogen
- Occurs in proximal, distal, and collecting tubules.
- CO2 combines with H2O to form H2CO3.
- H2CO3 dissociates into bicarbonate (HCO3−) and H+.
- H+ is secreted in exchange for Na+.
- Net production of HCO3− and net excretion of H+.
Na-H Exchange
- Exchange of sodium with hydrogen against concentration gradient via ATP hydrolysis.
- H+ ions extruded into tubular fluid in exchange for Na+ ions during acidosis.
- Process is inhibited during alkalosis.
Ammonia and Ammonium Excretion
- Ammonia is released by glutaminase enzyme action on glutamine in renal tubular cells.
- Ammonia diffuses across the cell membrane into tubular lumen.
- It is converted to ammonium ions which cannot cross the membrane, and is excreted with anions (e.g., phosphate, chloride, sulfate).
Bicarbonate Reabsorption
- Bicarbonate reabsorption primarily occurs in proximal convoluted tubules.
- Excreted hydrogen reacts with bicarbonate to form carbonic acid.
- Carbonic acid dissociates into CO2 and H2O.
- CO2 diffuses back and reforms carbonic acid, then bicarbonate.
- Approximately 90% of filtered bicarbonate is reclaimed, matching sodium reabsorption.
Important Buffer System
- Bicarbonate/carbonic acid is the main extracellular fluid buffer system.
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Description
Test your knowledge on the crucial roles and functions of water in living organisms. This quiz covers topics such as water balance regulation, daily water allowance, and the physiological importance of water. Perfect for students of biology and health sciences looking to refine their understanding of this essential substance.
