Clinical Correlates of pH Levels Problem Set
Problem 3: Rapid response to mild acidosis
Correct!
The bicarbonate buffering system of blood can respond quickly to mild metabolic acidosis (between pH 7.15 and 7.35) by:
A.
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expelling CO2 in the lung.
This removal of CO2 from the system then elicits a shift in the bicarbonate equilibrium, consuming H+ and HCO3- to replace the vanished CO2 (with
water as the other product). Since H+ ions are consumed, pH is raised. (HCO3- is also consumed, but this is not a problem with mild acidosis,
since the CO2 is constantly produced via the processes of normal metabolism and will gradually balance the bicarbonate reaction back the other way, restoring equilibrium.)
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B.
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retaining HCO3- in the kidney.
Although this measure does, in fact, help the situation, it is neither rapid
nor complete.
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C.
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excreting H+ in the kidney.
This does happen, but is slow and incomplete compared to the real way
the body deals with a little excess acid.
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D.
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direct buffering action of the H2CO3 central intermediate.
H2CO3 can only serve as an effective buffer within a pH unit of its pKa, which is about 6.1.
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E.
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retaining CO2 in the lung.
This would actually make the situation worse.
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The Biology Project
Department of Biochemistry and Molecular Biophysics
The University of Arizona
January 19, 1999
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All contents copyright © 1998. All rights reserved.
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