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Questions and Answers
What is the primary way nonvolatile acid hydrogen ions are excreted in urine?
What is the primary way nonvolatile acid hydrogen ions are excreted in urine?
- As dissociated sulfate ions
- As ammonium ions only
- As undissociated acid (correct)
- As organic phosphates
What compounds generate sulfuric acid in the body?
What compounds generate sulfuric acid in the body?
- Phosphate ions from metabolism
- Dicarboxylic acids produced in the liver
- Sulfate-containing compounds in foods (correct)
- Ammonium ions excreted in urine
Which of the following acids is classified as a nonvolatile acid?
Which of the following acids is classified as a nonvolatile acid?
- Acetic acid
- Carbonic acid
- Sulfuric acid (correct)
- Lactic acid
Which ions primarily contribute to buffering urinary pH?
Which ions primarily contribute to buffering urinary pH?
What is the relationship between phosphate excretion and phosphate ingestion?
What is the relationship between phosphate excretion and phosphate ingestion?
What is the range of urinary pH typically maintained through buffering?
What is the range of urinary pH typically maintained through buffering?
Which of the following is NOT a byproduct of sulfuric acid dissociation in the blood and urine?
Which of the following is NOT a byproduct of sulfuric acid dissociation in the blood and urine?
Which nonvolatile acid is a component of the tricarboxylic acid cycle?
Which nonvolatile acid is a component of the tricarboxylic acid cycle?
What role do dicarboxylic acids play in the context of nonvolatile acids?
What role do dicarboxylic acids play in the context of nonvolatile acids?
What is a consequence of increased H+ secretion and HCO3- reabsorption in the kidneys?
What is a consequence of increased H+ secretion and HCO3- reabsorption in the kidneys?
Which application of the Henderson-Hasselbalch equation is NOT mentioned?
Which application of the Henderson-Hasselbalch equation is NOT mentioned?
In terms of drug permeability, which form of a weak acid passes through membranes more readily?
In terms of drug permeability, which form of a weak acid passes through membranes more readily?
Which factor does NOT influence the ratio of charged to uncharged drug forms at an absorption site?
Which factor does NOT influence the ratio of charged to uncharged drug forms at an absorption site?
When the blood pH is below normal, which physiological state might be suggested?
When the blood pH is below normal, which physiological state might be suggested?
What is the role of the Henderson-Hasselbalch equation in pharmacology?
What is the role of the Henderson-Hasselbalch equation in pharmacology?
In a high pH environment, which form of a weak base is more likely to be uncharged?
In a high pH environment, which form of a weak base is more likely to be uncharged?
What is the impact of a high pCO2 on blood pH given the Henderson-Hasselbalch equation?
What is the impact of a high pCO2 on blood pH given the Henderson-Hasselbalch equation?
What effect does a weak acid (HA) have when it donates a proton (H+)?
What effect does a weak acid (HA) have when it donates a proton (H+)?
What is a key characteristic of a buffer solution?
What is a key characteristic of a buffer solution?
At what point during titration is the buffering effect maximal?
At what point during titration is the buffering effect maximal?
What ratio of [A-] to [HA] occurs when the pH of a buffered solution is one unit below the pKa?
What ratio of [A-] to [HA] occurs when the pH of a buffered solution is one unit below the pKa?
What happens to the pH when more hydrogen ions are added to a buffered solution near its pKa?
What happens to the pH when more hydrogen ions are added to a buffered solution near its pKa?
Which statement about the concentration of a buffer is true?
Which statement about the concentration of a buffer is true?
What occurs to the buffering capacity as the pH moves above the pKa?
What occurs to the buffering capacity as the pH moves above the pKa?
When equal amounts of a weak acid and its conjugate base are present, what is the expected pH level?
When equal amounts of a weak acid and its conjugate base are present, what is the expected pH level?
What characterizes the behavior of pH near 50% neutralization during titration?
What characterizes the behavior of pH near 50% neutralization during titration?
What occurs when a base is added to a buffered solution around its pKa?
What occurs when a base is added to a buffered solution around its pKa?
What is the pH of pure water at 25°C?
What is the pH of pure water at 25°C?
Which ion does the dissociation of water produce alongside hydroxyl ions?
Which ion does the dissociation of water produce alongside hydroxyl ions?
What is the concentration of hydrogen ions in pure water expressed in mol/L?
What is the concentration of hydrogen ions in pure water expressed in mol/L?
What is the equilibrium constant (K) for the dissociation of water at 25°C?
What is the equilibrium constant (K) for the dissociation of water at 25°C?
What is the main factor determining the acidity of a solution?
What is the main factor determining the acidity of a solution?
In the context of water ionization, what happens to protons when water dissociates?
In the context of water ionization, what happens to protons when water dissociates?
What is the assumption made about the concentration of water at equilibrium during dissociation?
What is the assumption made about the concentration of water at equilibrium during dissociation?
Which term describes the relationship between hydrogen ion concentration, hydroxide ion concentration, and the concentration of water at equilibrium?
Which term describes the relationship between hydrogen ion concentration, hydroxide ion concentration, and the concentration of water at equilibrium?
The concentration of which ion indicates higher acidity in a solution?
The concentration of which ion indicates higher acidity in a solution?
Which property of water allows biological macromolecules to assume specific shapes?
Which property of water allows biological macromolecules to assume specific shapes?
In which role does water NOT participate during photosynthesis?
In which role does water NOT participate during photosynthesis?
Which statement about water and its role in living cells is FALSE?
Which statement about water and its role in living cells is FALSE?
What aspect of the water molecule contributes to its dipole moment?
What aspect of the water molecule contributes to its dipole moment?
Which function does water serve in the context of blood composition?
Which function does water serve in the context of blood composition?
Why is heat dissipation an important property of water in biological systems?
Why is heat dissipation an important property of water in biological systems?
Which of the following statements best describes the role of water in biochemical reactions?
Which of the following statements best describes the role of water in biochemical reactions?
What is the major consequence of the electron dense cloud surrounding the oxygen atom in a water molecule?
What is the major consequence of the electron dense cloud surrounding the oxygen atom in a water molecule?
Which of the following does NOT contribute to water's effectiveness in separating charged molecules?
Which of the following does NOT contribute to water's effectiveness in separating charged molecules?
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Study Notes
Water and Acid-Base Equilibria
- Water constitutes around 60% of the mass of living cells and is crucial for biochemical reactions.
- Biological macromolecules rely on water for their specific shapes and chemical reactions.
- Water plays key roles as a reactant in many biochemical processes, particularly photosynthesis, which produces oxygen.
- It also acts as a medium for molecular transport, cellular separation, and heat dissipation.
Dipole Moment and Ionization of Water
- Water molecules are uncharged, yet they form hydrogen bonds with other polar molecules.
- The oxygen atom in water has two unshared electrons creating an electron-dense cloud.
- Water can ionize, producing hydrogen ions (H+) and hydroxyl ions (OH-), impacting the solution's acidity and pH levels.
- Pure water has a very low concentration of hydrogen ions (10^-7 mol/L), giving it a neutral pH of 7.
Dissociation Constants
- The dissociation constant of water (K) at 25°C is 1.8 x 10^-16 mol/L, emphasizing its limited dissociation.
- At equilibrium, water is considered constant at a concentration of 55.5 M.
Buffering Systems
- A buffer consists of a weak acid and its conjugate base, allowing solutions to resist pH changes when acids or bases are added.
- Buffer effectiveness peaks near pKa, maintaining a stable pH despite the addition of H+ or OH-.
- Nonvolatile acids in urine help buffer pH, typically ranging between 5.5 and 7.0.
Acidic Excretions and Their Sources
- Major nonvolatile acids include phosphates, uric acid, and sulfuric acid, contributing to the body’s acid-base balance.
- Sulfuric acid, generated from sulfur-containing compounds and amino acids, dissociates in the blood and urine to manage acidity.
- Phosphate ions and ammonium contribute significantly to buffering urinary pH, although not to blood pH.
Henderson-Hasselbalch Equation Applications
- This equation helps in preparing buffer solutions with specific pH values.
- It allows calculation of the degree of dissociation for weak acid-conjugate base pairs and how physiological solutions respond to pH changes.
- The bicarbonate buffer system is crucial for predicting pH shifts in relation to bicarbonate and carbon dioxide levels.
Drug Permeability and pH
- Understanding the ionic forms of weak acids and bases is essential for drug absorption; uncharged forms permeate membranes more effectively.
- The ratio of charged to uncharged drug forms is influenced by local pH and the drug's pKa, which is vital for its absorption in varying environments, like stomach vs. blood plasma.
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