ASCP MLS Clinical Chemistry – Questions With
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Terms in this set (520)
Which of the following B. The Henderson-Hasselbalch equation describes the
represents the Henderson- pH of a buffer comprised of a weak acid and its salt. pH
Hasselbalch equation as = pKa + log salt/acid, where pKa is the negative
applied to blood pH? logarithm of the dissociation constant of the acid. In this
case, the salt is sodium bicarbonate and the acid is the
A. pH = 6.1 + log dissolved CO2, which is equal to 0.03 (mmol/L per mm
HCO3-/PCO2 Hg) x PCO2. The pKa includes both the hydration and
B. pH = 6.1 + log dissociation constant for dissolved CO2 in blood, 6.1
HCO3-/(0.03 × PCO2) and is termed pK´.
C. pH = 6.1 + log
dCO2/HCO3-
D. pH = 6.1 + log (0.03 ×
PCO2)/HCO3-
What is the PO2 of C. Convert barometric pressure in inches to mm Hg by
calibration gas containing multiplying by 25.4 (mm/in.). Next, subtract the vapor
20.0% O2, when the pressure of H2O at 37°C, 47 mm Hg, to give dry gas
barometric pressure is 30 pressure. Multiply dry gas pressure by the %O2:
in.?
25.4 mm/in. × 30 in. = 762 mm Hg
A. 60 mm Hg 762 mm Hg - 47 mm Hg (vapor pressure) = 715 mm Hg
B. 86 mm Hg (dry gas pressure)
C. 143 mm Hg 0.20 × 715 mm Hg = 143 mm Hg PO2
D. 152 mm Hg
,What is the blood pH when C. Solve using the Henderson-Hasselbalch equation.
the partial pressure of pH = pK´ + log HCO3-/(0.03 × PCO2), where pK´, the
carbon dioxide (PCO2) is negative logarithm of the combined hydration and
60 mm Hg and the dissociation constants for dissolved CO2 and carbonic
bicarbonate concentration acid, is 6.1 and 0.03 is the solubility coefficient for CO2
is 18 mmol/L? gas.
A. 6.89 pH = 6.1 + log 18/(0.03 × 60) = 6.1 + log 18/1.8
B. 7.00 pH = 6.1 + log 10. Because log 10 = 1, pH = 7.10
C. 7.10
D. 7.30
Which of the following best A. The reference range for arterial blood pH is 7.35-7.45
represents the reference and is only 0.03 pH units lower for venous blood owing
(normal) range for arterial to the buffering effects of hemoglobin (Hgb) known as
pH? the chloride isohydric shift. Most laboratories consider
less than 7.20 and greater than 7.60 the critical values
A. 7.35-7.45 for pH.
B. 7.42-7.52
C. 7.38-7.68
D. 6.85-7.56
What is the normal ratio of C. When the ratio of HCO3-:dCO2 is 20:1, the log of
bicarbonate to dissolved salt/acid becomes 1.3. Substituting this in the
carbon dioxide Henderson-Hasselbalch equation and solving for pH
(HCO3-:dCO2) in arterial gives pH = 6.1 + log 20; pH = 6.1 + 1.3 = 7.4. Acidosis
blood? results when this ratio is decreased, and alkalosis when
it is increased.
A. 1:10
B. 10:1
C. 20:1
D. 30:1
C. Dissolved CO2 is calculated from the measured
What is the PCO2 if the
PCO2 × 0.0306, the solubility coefficient for CO2 gas in
dCO2 is 1.8 mmol/L?
blood at 37°C.
A. 24 mm Hg
dCO2 = PCO2 × 0.03
B. 35 mm Hg
Therefore, PCO2 = dCO2 /0.03
C. 60 mm Hg
PCO2 = 1.8 mmol/L ÷ 0.03 mmol/L per mm Hg = 60 mm
D. 72 mm Hg
Hg
,In the Henderson- A. The equilibrium constant, Kh, for the hydration of
Hasselbalch expression CO2 (dCO2 + H2O →H2CO3) is only about 2.3 × 10-3M,
making dCO2 far more prevalent than carbonic acid.
pH = 6.1 + log The dissociation constant, Kd, for the reaction H2CO3
HCO3-/dCO2, the 6.1 →H+ + HCO3 - is about 2 × 10-4 M. The product of these
represents: constants is the combined equilibrium constant, K´. The
negative logarithm of K´ is the pK´, which is 6.103 in
A. The combined hydration blood at 37°C.
and dissociation constants
for CO2 in blood at 37°C
B. The solubility constant
for CO2 gas
C. The dissociation constant
of H2O
D. The ionization constant
of sodium bicarbonate
(NaHCO3)
C. The total CO2 is the sum of the dCO2, H2CO3
(carbonic acid or hydrated CO2), and bicarbonate (as
mainly NaHCO3). When serum is used to measure total
CO2, the dCO2 is insignificant because all the CO2 gas
has escaped into the air. Therefore, serum total CO2 is
Which of the following
equivalent to the bicarbonate concentration. Total CO2
contributes the most to the
is commonly measured by potentiometry. An organic
serum total CO2?
acid is used to release CO2 gas from bicarbonate and
pCO2 is measured with a Severinghaus electrode.
A. PCO2
Alternately, bicarbonate can be measured by an
B. dCO2
enzymatic reaction using phosphoenol pyruvate
C. HCO3-
carboxylase. The enzyme forms oxaloacetate and
D. Carbonium ion
phosphate from phosphoenol pyruvate and
bicarbonate. The oxaloacetate is reduced to malate by
malate dehydrogenase and NADH is oxidized to NAD+.
The negative reaction rate is proportional to plasma
bicarbonate concentration.
, In addition to sodium A. The primary blood buffer bases preventing acidosis
bicarbonate, what other in order of concentration are bicarbonate,
substance contributes most deoxyhemoglobin, albumin, and monohydrogen
to the amount of base in phosphate. At physiological pH, there is significantly
the blood? more H2PO4^-1 than HPO4^-2, and phosphate is a more
efficient buffer system at preventing alkalosis than
A. Hemoglobin acidosis. Since all of the blood buffer systems are in
concentration equilibrium, the pH can be calculated accurately from
B. Dissolved O2 the concentration of bicarbonate and dissolved CO2
concentration using the Henderson-Hasselbalch equation.
C. Inorganic phosphorus
D. Organic phosphate
Which of the following A. The PO2 of air at sea level (21% O2) is about 150 mm
effects results from Hg. The PCO2 of air is only about 0.3 mm Hg.
exposure of a normal Consequently, blood releases CO2 gas and gains O2
arterial blood sample to when exposed to air. Loss of CO2 shifts the equilibrium
room air? of the bicarbonate buffer system to the right,
decreasing hydrogen ion concentration and blood
A. PO2 increased PCO2 becomes more alkaline.
decreased pH increased
B. PO2 decreased PCO2
increased pH decreased
C. PO2 increased PCO2
decreased pH decreased
D. PO2 decreased PCO2
decreased pH decreased
Detailed Solutions
Save
Terms in this set (520)
Which of the following B. The Henderson-Hasselbalch equation describes the
represents the Henderson- pH of a buffer comprised of a weak acid and its salt. pH
Hasselbalch equation as = pKa + log salt/acid, where pKa is the negative
applied to blood pH? logarithm of the dissociation constant of the acid. In this
case, the salt is sodium bicarbonate and the acid is the
A. pH = 6.1 + log dissolved CO2, which is equal to 0.03 (mmol/L per mm
HCO3-/PCO2 Hg) x PCO2. The pKa includes both the hydration and
B. pH = 6.1 + log dissociation constant for dissolved CO2 in blood, 6.1
HCO3-/(0.03 × PCO2) and is termed pK´.
C. pH = 6.1 + log
dCO2/HCO3-
D. pH = 6.1 + log (0.03 ×
PCO2)/HCO3-
What is the PO2 of C. Convert barometric pressure in inches to mm Hg by
calibration gas containing multiplying by 25.4 (mm/in.). Next, subtract the vapor
20.0% O2, when the pressure of H2O at 37°C, 47 mm Hg, to give dry gas
barometric pressure is 30 pressure. Multiply dry gas pressure by the %O2:
in.?
25.4 mm/in. × 30 in. = 762 mm Hg
A. 60 mm Hg 762 mm Hg - 47 mm Hg (vapor pressure) = 715 mm Hg
B. 86 mm Hg (dry gas pressure)
C. 143 mm Hg 0.20 × 715 mm Hg = 143 mm Hg PO2
D. 152 mm Hg
,What is the blood pH when C. Solve using the Henderson-Hasselbalch equation.
the partial pressure of pH = pK´ + log HCO3-/(0.03 × PCO2), where pK´, the
carbon dioxide (PCO2) is negative logarithm of the combined hydration and
60 mm Hg and the dissociation constants for dissolved CO2 and carbonic
bicarbonate concentration acid, is 6.1 and 0.03 is the solubility coefficient for CO2
is 18 mmol/L? gas.
A. 6.89 pH = 6.1 + log 18/(0.03 × 60) = 6.1 + log 18/1.8
B. 7.00 pH = 6.1 + log 10. Because log 10 = 1, pH = 7.10
C. 7.10
D. 7.30
Which of the following best A. The reference range for arterial blood pH is 7.35-7.45
represents the reference and is only 0.03 pH units lower for venous blood owing
(normal) range for arterial to the buffering effects of hemoglobin (Hgb) known as
pH? the chloride isohydric shift. Most laboratories consider
less than 7.20 and greater than 7.60 the critical values
A. 7.35-7.45 for pH.
B. 7.42-7.52
C. 7.38-7.68
D. 6.85-7.56
What is the normal ratio of C. When the ratio of HCO3-:dCO2 is 20:1, the log of
bicarbonate to dissolved salt/acid becomes 1.3. Substituting this in the
carbon dioxide Henderson-Hasselbalch equation and solving for pH
(HCO3-:dCO2) in arterial gives pH = 6.1 + log 20; pH = 6.1 + 1.3 = 7.4. Acidosis
blood? results when this ratio is decreased, and alkalosis when
it is increased.
A. 1:10
B. 10:1
C. 20:1
D. 30:1
C. Dissolved CO2 is calculated from the measured
What is the PCO2 if the
PCO2 × 0.0306, the solubility coefficient for CO2 gas in
dCO2 is 1.8 mmol/L?
blood at 37°C.
A. 24 mm Hg
dCO2 = PCO2 × 0.03
B. 35 mm Hg
Therefore, PCO2 = dCO2 /0.03
C. 60 mm Hg
PCO2 = 1.8 mmol/L ÷ 0.03 mmol/L per mm Hg = 60 mm
D. 72 mm Hg
Hg
,In the Henderson- A. The equilibrium constant, Kh, for the hydration of
Hasselbalch expression CO2 (dCO2 + H2O →H2CO3) is only about 2.3 × 10-3M,
making dCO2 far more prevalent than carbonic acid.
pH = 6.1 + log The dissociation constant, Kd, for the reaction H2CO3
HCO3-/dCO2, the 6.1 →H+ + HCO3 - is about 2 × 10-4 M. The product of these
represents: constants is the combined equilibrium constant, K´. The
negative logarithm of K´ is the pK´, which is 6.103 in
A. The combined hydration blood at 37°C.
and dissociation constants
for CO2 in blood at 37°C
B. The solubility constant
for CO2 gas
C. The dissociation constant
of H2O
D. The ionization constant
of sodium bicarbonate
(NaHCO3)
C. The total CO2 is the sum of the dCO2, H2CO3
(carbonic acid or hydrated CO2), and bicarbonate (as
mainly NaHCO3). When serum is used to measure total
CO2, the dCO2 is insignificant because all the CO2 gas
has escaped into the air. Therefore, serum total CO2 is
Which of the following
equivalent to the bicarbonate concentration. Total CO2
contributes the most to the
is commonly measured by potentiometry. An organic
serum total CO2?
acid is used to release CO2 gas from bicarbonate and
pCO2 is measured with a Severinghaus electrode.
A. PCO2
Alternately, bicarbonate can be measured by an
B. dCO2
enzymatic reaction using phosphoenol pyruvate
C. HCO3-
carboxylase. The enzyme forms oxaloacetate and
D. Carbonium ion
phosphate from phosphoenol pyruvate and
bicarbonate. The oxaloacetate is reduced to malate by
malate dehydrogenase and NADH is oxidized to NAD+.
The negative reaction rate is proportional to plasma
bicarbonate concentration.
, In addition to sodium A. The primary blood buffer bases preventing acidosis
bicarbonate, what other in order of concentration are bicarbonate,
substance contributes most deoxyhemoglobin, albumin, and monohydrogen
to the amount of base in phosphate. At physiological pH, there is significantly
the blood? more H2PO4^-1 than HPO4^-2, and phosphate is a more
efficient buffer system at preventing alkalosis than
A. Hemoglobin acidosis. Since all of the blood buffer systems are in
concentration equilibrium, the pH can be calculated accurately from
B. Dissolved O2 the concentration of bicarbonate and dissolved CO2
concentration using the Henderson-Hasselbalch equation.
C. Inorganic phosphorus
D. Organic phosphate
Which of the following A. The PO2 of air at sea level (21% O2) is about 150 mm
effects results from Hg. The PCO2 of air is only about 0.3 mm Hg.
exposure of a normal Consequently, blood releases CO2 gas and gains O2
arterial blood sample to when exposed to air. Loss of CO2 shifts the equilibrium
room air? of the bicarbonate buffer system to the right,
decreasing hydrogen ion concentration and blood
A. PO2 increased PCO2 becomes more alkaline.
decreased pH increased
B. PO2 decreased PCO2
increased pH decreased
C. PO2 increased PCO2
decreased pH decreased
D. PO2 decreased PCO2
decreased pH decreased
