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Questions and Answers
What is the main function of buffers in bodily fluids?
What is the main function of buffers in bodily fluids?
- To facilitate the breakdown of proteins
- To resist rapid changes in pH (correct)
- To completely eliminate acids from the body
- To increase the temperature of body fluids
What is pKa, and why is it important in biological buffering?
What is pKa, and why is it important in biological buffering?
- It reflects the protonation state of a buffering agent at a specific pH (correct)
- It indicates the strength of an acid in terms of its complete dissociation
- It is the pH at which a weak acid is completely dissociated
- It demonstrates the rate of reaction of acids with bases
What is the normal pH range for human blood?
What is the normal pH range for human blood?
- 7.0 to 7.8
- 7.0 to 8.0
- 6.5 to 7.0
- 7.35 to 7.45 (correct)
Which of the following is a consequence of acidosis?
Which of the following is a consequence of acidosis?
Which organs are primarily responsible for regulating acid-base balance in the body?
Which organs are primarily responsible for regulating acid-base balance in the body?
What role do proteins serve in physiological buffering?
What role do proteins serve in physiological buffering?
How do hemoglobin molecules function as buffers in the blood?
How do hemoglobin molecules function as buffers in the blood?
Which of the following components primarily generates acids in the human body?
Which of the following components primarily generates acids in the human body?
What is the effect of an increase in pH on hydroxide ion concentration?
What is the effect of an increase in pH on hydroxide ion concentration?
At what pH level does the concentration of hydrogen ions equal that of hydroxide ions?
At what pH level does the concentration of hydrogen ions equal that of hydroxide ions?
Which of the following describes a strong acid?
Which of the following describes a strong acid?
Which statement correctly describes the dissociation of water?
Which statement correctly describes the dissociation of water?
What is the formula relating hydrogen ion concentration and pH?
What is the formula relating hydrogen ion concentration and pH?
What does the pKa value indicate about an acid?
What does the pKa value indicate about an acid?
Which statement accurately describes the relationship between pKa and acid strength?
Which statement accurately describes the relationship between pKa and acid strength?
When the hydrogen ion concentration is $10^{-2}$ M, what is the corresponding pH value?
When the hydrogen ion concentration is $10^{-2}$ M, what is the corresponding pH value?
Which of the following correctly describes weak acids?
Which of the following correctly describes weak acids?
In the context of buffers, what occurs at the pKa of a weak acid?
In the context of buffers, what occurs at the pKa of a weak acid?
What is the purpose of the Henderson-Hasselbalch equation?
What is the purpose of the Henderson-Hasselbalch equation?
What is the ionic product of water at neutrality?
What is the ionic product of water at neutrality?
During the titration of phosphoric acid with KOH, what species is produced upon complete dissociation?
During the titration of phosphoric acid with KOH, what species is produced upon complete dissociation?
Which of the following correctly describes a weak acid?
Which of the following correctly describes a weak acid?
What is the dissociation constant (Ka) a measure of?
What is the dissociation constant (Ka) a measure of?
When titrating with NaOH, what is the primary factor that changes the pH?
When titrating with NaOH, what is the primary factor that changes the pH?
Which pKa value indicates that deoxyhaemoglobin is a weaker acid compared to oxyhaemoglobin?
Which pKa value indicates that deoxyhaemoglobin is a weaker acid compared to oxyhaemoglobin?
What is the base/acid ratio for oxyhaemoglobin at a blood pH of 7.4?
What is the base/acid ratio for oxyhaemoglobin at a blood pH of 7.4?
At which pH value does aspirin diffuse more easily across biological membranes?
At which pH value does aspirin diffuse more easily across biological membranes?
What effect do neighboring groups have on the pKa of histidine in hemoglobin compared to free histidine?
What effect do neighboring groups have on the pKa of histidine in hemoglobin compared to free histidine?
What is the pKa of oxyhaemoglobin, and how does it relate to its buffering capacity for H+?
What is the pKa of oxyhaemoglobin, and how does it relate to its buffering capacity for H+?
What log ratio for deoxyhaemoglobin indicates a higher acid concentration compared to a base concentration at a blood pH of 7.4?
What log ratio for deoxyhaemoglobin indicates a higher acid concentration compared to a base concentration at a blood pH of 7.4?
What happens when H+ ions are added to a buffer system?
What happens when H+ ions are added to a buffer system?
Which physiological buffer system has a pKa value closest to neutral pH?
Which physiological buffer system has a pKa value closest to neutral pH?
Why is glycine a poor physiological buffer?
Why is glycine a poor physiological buffer?
What determines the buffering effectiveness of an acid at a specific pH?
What determines the buffering effectiveness of an acid at a specific pH?
What characteristic of hemoglobin contributes to its role as a buffer in blood?
What characteristic of hemoglobin contributes to its role as a buffer in blood?
What does the Henderson-Hasselbalch equation primarily express?
What does the Henderson-Hasselbalch equation primarily express?
Which amino acid group does not contribute effectively to physiological buffering?
Which amino acid group does not contribute effectively to physiological buffering?
Which form of carbonic acid is dominant when regulating blood pH?
Which form of carbonic acid is dominant when regulating blood pH?
Study Notes
pH and its Measurement
- pH indicates the concentration of hydrogen ions in a solution, influencing its acidity or alkalinity.
- True acidity is determined by free hydrogen ions, not those bound to anions.
- Normal blood pH ranges from 7.35 to 7.45; levels outside this can be dangerous (acidosis <7.35, alkalosis >7.45).
Sources of Acids in the Body
- Acids mainly originate from:
- Breakdown of proteins
- Incomplete oxidation of fats and glucose
- Transport of carbon dioxide in the blood
- The body regulates acid-base balance through the lungs, kidneys, and chemical buffer systems.
Buffering System
- Buffers stabilize pH by:
- Releasing hydrogen ions as acids when pH rises
- Binding hydrogen ions as bases when pH drops
- Ideal buffering occurs at the pKa where acid and conjugate base are present in equal amounts.
Understanding Acids and Bases
- Strong acids fully dissociate (e.g., HCl → H+ + Cl-), while weak acids partially dissociate (e.g., H2CO3 → H+ + HCO3-).
- Strong bases are more effective proton acceptors than weak bases.
Water Ionization
- Pure water is a 55.6M solution and dissociates slightly into H+ and OH- ions.
- At neutrality, both [H+] and [OH-] equal 10^-7 M, yielding a pH of 7.
pKa and its Importance
- pKa is the negative logarithm of the dissociation constant (Ka); it indicates the pH at which an acid is half dissociated.
- The lower the pKa, the stronger the acid.
Henderson-Hasselbalch Equation
- Formula: pH = pKa + log([A-]/[HA])
- This equation connects pH, pKa, and the concentrations of an acid and its conjugate base, guiding buffer capacity.
Physiological Buffers
- Key physiological buffers include:
- H2CO3 ↔ HCO3- (pKa 6.1)
- H2PO4- ↔ HPO42- (pKa 6.8)
- Proteins also function as buffers, with a specific dependence on amino acid side chains.
Role of Amino Acids
- Glycine's buffering capacity is limited outside its pKa values (2.34 and 9.66).
- The active buffering in physiological conditions is largely attributed to R groups of amino acids.
Hemoglobin as a Buffer
- Hemoglobin effectively buffers H+ produced during metabolism due to its histidine residues.
- The pKa of histidine in hemoglobin is altered by neighboring groups:
- Oxyhemoglobin has a pKa of 6.8
- Deoxyhemoglobin has a pKa of 7.8
Analyzing Hemoglobin's Buffering Capacity
- For normal blood pH (7.4):
- OxyHb with pKa 6.8 provides a ratio of base/acid (3.98:1).
- DeoxyHb with pKa 7.8 has a ratio of 1:2.51, making oxyhemoglobin a better buffer for metabolic acid.
Diffusion of Lipid-soluble Molecules
- Lipid-soluble substances can easily diffuse across biological membranes, while those strongly interacting with water struggle to do so.
- Aspirin diffusion is affected by pH, diffusing more readily at pH 8 than at pH 2.
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Description
This quiz evaluates your understanding of pH and buffering, focusing on the differences between strong and weak acids, the significance of pKa, and the application of the Henderson-Hasselbalch equation. Additionally, it covers physiological buffers and the role of proteins and hemoglobin in buffering systems. Test your knowledge on these essential topics in biology and chemistry.
