Questions and Answers
What is the primary factor that acidity depends on?
What is the normal pH range of blood?
Which of the following is NOT a source of acid in the body?
What is the purpose of chemical buffers in the body?
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What is the role of the kidneys in acid-base balance?
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What is the term for a condition where the blood pH falls below 7.35?
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What is the importance of pKa in biological buffering?
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How do proteins act as physiological buffers?
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What is the ionic product of water?
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What is the pH of a solution with a hydrogen ion concentration of 10-2M?
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What is the concentration of hydroxide ions in a solution with a hydrogen ion concentration of 10-4M?
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What is the definition of a strong acid?
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What is the pH of blood?
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What is the concentration of hydrogen ions in blood?
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What is the main component of buffers?
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What percentage of body mass is water in a healthy young woman?
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What is the significance of the pKa value?
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What is the purpose of the Henderson-Hasselbalch equation?
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What is the characteristic of a strong acid?
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What is the significance of the buffering region?
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What is the relationship between the pKa and the strength of an acid?
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What is the purpose of a buffer solution?
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What is the significance of the equivalence point in a titration curve?
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What is the relationship between the conjugate base and acid in a buffer solution?
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What is the main reason why the pKa of histidine in Hb is different from that of free His?
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Which of the following is a better buffer for H+ produced in metabolism?
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What is the ratio of base to acid for oxyhaemoglobin at a pH of 7.4?
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What can be predicted about the diffusion of aspirin across biological membranes?
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What is the pH of blood at which the ratio of base to acid for oxyhaemoglobin is 1:1?
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Which of the following statements about deoxyhaemoglobin is true?
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What is the primary function of a buffer in a physiological system?
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At what pH does an acid buffer best?
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What is the purpose of the Henderson-Hasselbalch equation?
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Why is glycine not a good physiological buffer?
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What is the role of the alpha carboxyl and alpha amino groups in proteins?
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What is the characteristic of amino acid side chains that makes them poor physiological buffers?
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What is the primary reason why histidine residues make haemoglobin a good blood buffer?
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What is the advantage of using the Henderson-Hasselbalch equation in diagnosing acidosis?
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Study Notes
pH and Buffering
- pH is a measure of hydrogen ion concentration (acidity or alkalinity of a solution)
- Acidity depends only on free hydrogen ions, not those still bound to anions
- Blood pH is normally maintained within a narrow range of 7.35 to 7.45, and outside this range can be fatal
- Living range of pH: 7.0-7.8
Acid-Base Balance
- Acid-base balance is regulated in the body by the lungs, kidneys, and chemical buffers in the blood
- Buffers resist abrupt and large swings in pH of body fluids by releasing H+ (acting as acids) when pH rises and binding H+ (acting as bases) when pH drops
Buffering Mechanism
- Buffers operate by releasing H+ when pH rises and binding H+ when pH drops
- Strong acids are completely dissociated in solution, while weak acids are partially dissociated
- Strong bases are more effective proton acceptors than weak bases
Ionisation of Water
- Pure water is a 55.6M solution that dissociates to a very small extent
- At neutrality, [H+] = [OH-] = 10-7M
- pH = -log[H+]
Dissociation of Acids
- Acids are proton (H+) donors, while bases are proton acceptors
- Strong acids dissociate completely in solution, while weak acids dissociate partially
- pKa is the pH at which an acid is half-dissociated, and is a measure of an acid's strength
Henderson-Hasselbalch Equation
- pH = pKa + log([A-] / [HA])
- The equation relates the pH of a solution, the pKa of a weak acid, and the relative amounts of dissociated and non-dissociated forms of the acid
- At the pKa, buffering is best, as there are equal amounts of dissociated and non-dissociated forms of the acid
Physiologically Important Buffers
- Physiologically important buffers include H2CO3/HCO3- (pKa 6.1), H2PO4-/HPO42- (pKa 6.8), and protein buffers
- Haemoglobin is an important buffer in the blood, with a pKa of 6.8 for oxyhaemoglobin and 7.8 for deoxyhaemoglobin
Haemoglobin as a Buffer
- Haemoglobin is a good blood buffer due to the presence of histidine residues
- The pKa of histidine in haemoglobin is different from that of free histidine, due to the effects of neighbouring groups
- Oxyhaemoglobin is a better buffer for H+ produced in metabolism than deoxyhaemoglobin
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Description
This quiz covers the basics of pH and buffering in biological systems, including strong and weak acids, pKa, Henderson-Hasselbalch equation, physiological buffers, and proteins as buffers.
