IBSS 1540 EXAM 3 2025 QUESTIONS AND
ANSWERS
What is normal body pH? - ANS 7.35-7.45
What is normal pressure of carbon dioxide in the body? - ANS 35-45 mmHg
What is the normal level of bicarbonate in the body? - ANS 22-26 mEq/L
What does Mass action describe? - ANS the effect of respiratory disorders and associated
changes in carbon dioxide on bicarb in the body
According to mass action, what happens when PCO2 changes in increments of 10 mmHg? -
ANS If carbon dioxide raises by 10 mmHg, bicarb will increase by 1 mEq/L. If it decreases by
ten, then bicarb will decrease by two units
What is the normal value of the anion gap? - ANS 12 +/- 4
What is the anion gap? - ANS the charge difference that exists based on the amount of Na,
Cl, and bicarb in the body
1
Page
@COPYRIGHT SIRJOEL 2025/2026
, Why is the concentration of H+ tightly regulated within the body? - ANS because H+ ions are
very reactive and can interfere with the structure and function of proteins if their concentration
is left unchecked
What is the difference between the degree of regulation of Na concentration in the body vs H+?
- ANS H+ is regulated with much tighter control than most other body substances because it
is so highly reactive
What is the Henderson-Hasselbach equation? - ANS Ph= pka+ log [HCO3-]/ 0.03 PCO2
What is pKa, as occurs in the Henderson Hasselbach equation? - ANS it is an acid dissociation
constant
What fraction is pH proportional to? - ANS bicarb/carbon dioxide; or in other words, base
divided by acid
Changes in which two variables can be responsible for a shift in body pH? - ANS in either
bicarb or carbon dioxide
What two factors determine the efficiency of a buffer? - ANS its pKa and cocnentration
What is the role of a buffer's pKa? - ANS it will be most effective at buffering acids near that
pKa
Why is bicarbonate the most efficient buffer in the body? - ANS because it is present in such
high concentration
2
What forms of regulation of bicarbonate allow it to be the most efficient buffer? - ANS the
Page
fact that it is both directly regulated by the kidneys and indirectly regulated by the lungs
@COPYRIGHT SIRJOEL 2025/2026
, what happens when bicarbonate binds acid? - ANS it forms carbonic acid, which dissociates
in to carbon dioxide and water
What are the three main buffers found in the blood? - ANS bicarbonate, hemoglobin,
phosphate/proteins
How much of the blood's buffering capacity occurs due to bicarbonate? - ANS 50%
How much of the blood's buffering capacity occurs due to hemoglobin? - ANS 35%
How much of the blood's buffering capacity occurs due to phosphate or other proteins? -
ANS 15%
What is the most important non-bicarbonate buffer in the blood? - ANS hemoglobin
What aspect of bone allows it to act as a buffer? - ANS H+ ions can displace the surface
cations of bone, thereby binding up the acid and preventing it from causing problems
How effective is bone as a buffer? - ANS it takes a long time to have its effect, sometimes up
to 4 hours
In which situation is bone a more effective buffer? - ANS in chronic acidosis
What portion of the buffering is accomplished by bone in cases of chronic acidosis? -
ANS 40%
3
Page
@COPYRIGHT SIRJOEL 2025/2026
, Is bicarbonate an intracellular or extracellular buffer? - ANS extracellular, since it is found at
very low concentrations within ells
What is the main intracellular buffer? - ANS proteins
After proteins, what is the next best intracellular buffer? - ANS phosphate
What kind of buffering occurs in cases of metabolic acidosis? - ANS all bicarbonate in the
body binds to acid in order to buffer it. The bone and cells also play a role in buffering
What causes metabolic acidosis? - ANS conditions like diarrhea, which cause bicarbonate to
be lost and causes the pH to decrease
During metabolic acidosis, is extracellular or intracellular buffering more active? - ANS most
of the buffering occurs within cells
What is the role of bicarbonate in buffering respiratory acidosis? - ANS it does not play a
large role because bicarbonate would regenerate carbonic acid if it tried to buffer it
What is the role of red blood cells in buffering respiratory acidosis? - ANS the hemoglobin
within these cells binds protons and accomplishes 35% of the buffering
What is the primary mechanism of buffering in respiratory acidosis? - ANS mostly
intracellular, with only about 3% occurring extracellularly
What occurs in transcellular exchange in cases of acidosis caused by diabetes or COPD? -
ANS the increased concentration of protons creates a concentration gradient that causes
4
influx into cells. The increase in positive charge within the cells causes K+ efflux, resulting in
Page
hyperkalemia
@COPYRIGHT SIRJOEL 2025/2026
ANSWERS
What is normal body pH? - ANS 7.35-7.45
What is normal pressure of carbon dioxide in the body? - ANS 35-45 mmHg
What is the normal level of bicarbonate in the body? - ANS 22-26 mEq/L
What does Mass action describe? - ANS the effect of respiratory disorders and associated
changes in carbon dioxide on bicarb in the body
According to mass action, what happens when PCO2 changes in increments of 10 mmHg? -
ANS If carbon dioxide raises by 10 mmHg, bicarb will increase by 1 mEq/L. If it decreases by
ten, then bicarb will decrease by two units
What is the normal value of the anion gap? - ANS 12 +/- 4
What is the anion gap? - ANS the charge difference that exists based on the amount of Na,
Cl, and bicarb in the body
1
Page
@COPYRIGHT SIRJOEL 2025/2026
, Why is the concentration of H+ tightly regulated within the body? - ANS because H+ ions are
very reactive and can interfere with the structure and function of proteins if their concentration
is left unchecked
What is the difference between the degree of regulation of Na concentration in the body vs H+?
- ANS H+ is regulated with much tighter control than most other body substances because it
is so highly reactive
What is the Henderson-Hasselbach equation? - ANS Ph= pka+ log [HCO3-]/ 0.03 PCO2
What is pKa, as occurs in the Henderson Hasselbach equation? - ANS it is an acid dissociation
constant
What fraction is pH proportional to? - ANS bicarb/carbon dioxide; or in other words, base
divided by acid
Changes in which two variables can be responsible for a shift in body pH? - ANS in either
bicarb or carbon dioxide
What two factors determine the efficiency of a buffer? - ANS its pKa and cocnentration
What is the role of a buffer's pKa? - ANS it will be most effective at buffering acids near that
pKa
Why is bicarbonate the most efficient buffer in the body? - ANS because it is present in such
high concentration
2
What forms of regulation of bicarbonate allow it to be the most efficient buffer? - ANS the
Page
fact that it is both directly regulated by the kidneys and indirectly regulated by the lungs
@COPYRIGHT SIRJOEL 2025/2026
, what happens when bicarbonate binds acid? - ANS it forms carbonic acid, which dissociates
in to carbon dioxide and water
What are the three main buffers found in the blood? - ANS bicarbonate, hemoglobin,
phosphate/proteins
How much of the blood's buffering capacity occurs due to bicarbonate? - ANS 50%
How much of the blood's buffering capacity occurs due to hemoglobin? - ANS 35%
How much of the blood's buffering capacity occurs due to phosphate or other proteins? -
ANS 15%
What is the most important non-bicarbonate buffer in the blood? - ANS hemoglobin
What aspect of bone allows it to act as a buffer? - ANS H+ ions can displace the surface
cations of bone, thereby binding up the acid and preventing it from causing problems
How effective is bone as a buffer? - ANS it takes a long time to have its effect, sometimes up
to 4 hours
In which situation is bone a more effective buffer? - ANS in chronic acidosis
What portion of the buffering is accomplished by bone in cases of chronic acidosis? -
ANS 40%
3
Page
@COPYRIGHT SIRJOEL 2025/2026
, Is bicarbonate an intracellular or extracellular buffer? - ANS extracellular, since it is found at
very low concentrations within ells
What is the main intracellular buffer? - ANS proteins
After proteins, what is the next best intracellular buffer? - ANS phosphate
What kind of buffering occurs in cases of metabolic acidosis? - ANS all bicarbonate in the
body binds to acid in order to buffer it. The bone and cells also play a role in buffering
What causes metabolic acidosis? - ANS conditions like diarrhea, which cause bicarbonate to
be lost and causes the pH to decrease
During metabolic acidosis, is extracellular or intracellular buffering more active? - ANS most
of the buffering occurs within cells
What is the role of bicarbonate in buffering respiratory acidosis? - ANS it does not play a
large role because bicarbonate would regenerate carbonic acid if it tried to buffer it
What is the role of red blood cells in buffering respiratory acidosis? - ANS the hemoglobin
within these cells binds protons and accomplishes 35% of the buffering
What is the primary mechanism of buffering in respiratory acidosis? - ANS mostly
intracellular, with only about 3% occurring extracellularly
What occurs in transcellular exchange in cases of acidosis caused by diabetes or COPD? -
ANS the increased concentration of protons creates a concentration gradient that causes
4
influx into cells. The increase in positive charge within the cells causes K+ efflux, resulting in
Page
hyperkalemia
@COPYRIGHT SIRJOEL 2025/2026
