Cremo 1: Fundamentals of body buffers and gases Flashcards
What is the concentration of H+ ions in a healthy individual?
35 and 45 nM
Normal range for pH
7.35-7.45
Acid production originates intracellularly. What is the average intracellular pH?
7
Non bicarbonate buffers
hemoglobin
plasma proteins
phosphates
This has the highest buffer capacity of non-volatile buffers
hemoglobin
What two things does buffering capacity depend on?
- concentration of the buffer
2. PKA (how close is the PKA to 7.4?)
Hemoglobin has abundant (blank) side chains, therefore it has a PKA of about (blank)
histidine; 6.5
Plasma proteins have about (blank) percent of the buffering capacity of Hb
20%
The most plentiful plasma protein
Albumin
An important buffer in the renal tubular filtrate
Phosphate
List the non-bicarbonate (non-volatile) buffers in order of buffering capacity
- hemoglobin
- plasma proteins
- phosphate
What is the most important function of the non-volatile buffers?
Mitigate pH changes due to changes in volatile acid (CO2)
Can the bicarbonate system mitigate changes in the levels of CO2?
No! Non-volatile buffers are the only ones that can do this.
Most powerful buffer of the ECF
Bicarbonate buffer system
Atmospheric pressure
760mmHg
Total of partial pressures (barometric pressure) at sea level? Total of partial pressure in Reno?
760mmHg; 680mmHg
Partial pressure of CO2.
0.23mmHg
Clinical PCO2
Zero (0.23 at sea level)
PO2 at sea level? In Reno?
159mmHg; 143mmHg
In an unopened bottle of soda water, the partial pressure of the gas above the liquid is
the same as the liquid.
The partial pressure of a gas dissolved in a liquid is the partial pressure of that gas which would be generated in a gas phase (blank) with the liquid.
in equilibrium
Gases always travel down (blank) gradients, but may or may not travel down (blank) gradients.
partial pressure gradients; concentration gradients
What does Henry’s law quantify?
How much gas is dissolved in a liquid
What’s the formula for Henry’s law?
P•KH = C = Concentration
Where KH is different for each gas.
At equilibrium, the solubility of a gas in a liquid is directly proportional to the partial pressure of the gas above the liquid.
Henry’s law
K acid equation for the bicarbonate buffer system
K = ([H+][HCO3-])/CO2
Simplified bicarbonate buffer system
CO2 H+ + HCO3-
Normal concentration of bicarbonate in the body in a healthy individual
24mM
In a healthy individual, the ratio of bicarbonate to CO2 is…
20
The Henderson equation
Kacid = ([H+][HCO3-])/PaCO2
Normal [H+] concentration
Normal [HCO3-] concentration
Normal PaCO2
40nM
24mM
40mmHg
When a sample of whole blood is exposed to an increased PCO2, what will happen?
This will shift the equilibrium to the right, increasing H+ and HCO3-
Henderson Hasselbalch Equation for clinical use
pH = 6.1 + log [HCO3-]/(0.3*PaCO2)
Rearranged Henderson equation to solve for [H+]
(24 * PaCO2)/HCO3- = [H+]
The bicarbonate system is open to the atmosphere, so it allows for the removal of (blank) to give effective buffering even though the PKA of 6.1 is far from 7.4
CO2
What kind of buffers responds to changes in CO2?
Non-volatile buffers, like hemoglobin
Describe what happens when Hb is present during hypoventilation.
During hypoventilation, there is an increase in the PCO2, so the system produces more H+ and more HCO3-. Hb can act as a buffer by pulling out some of the H+ to make HbH+.
Is a shift in equilibrium equal to a buffering effect?
No!
Two main processes that acidify the body
- Metabolism produces CO2
2. Endogenous acid production
Does metabolism consume bicarbonate? Does endogenous acid production consume bicarbonate?
No; Yes
Major source of metabolic acid production
Eating protein
Industrialized diets (high in meat and eggs) have (blank) rates of metabolic acid production, while non-industrialized diets (more fruits and veggies) have (blank) rates of metabolic acid production.
high; low
Compare the daily production of CO2 to the daily production of metabolic acid
Daily CO2»»metabolic acid
Volatile acid is about 100 times that of non-volatile.
Acid secreted by the gut into the blood
Gastrointestinal acid production
Does GAP consume bicarbonate?
yes
(blank) serves as a buffer for gastrointestinal acid production
Bicarbonate system
In the upper gut, (blank) enters the lumen of the gut, while (blank) is pushed out into the bloodstream. In the lower gut, (blank) enters the lumen of the gut and (blank) is pushed out into the bloodstream.
H+, HCO3-
HCO3-, H+
On balance, the gut secretes slightly more (blank) into the blood stream than (blank)
H+ ; HCO3-
Endogenous acid production equation
EAP = MAP + GAP
Prolonged vomiting can lead to metabolic (blank), while diarrhea can lead to prolonged metabolic (blank).
alkalosis; acidosis
Vomiting causes (blank) to leave the stomach lumen, and (blank) to enter the blood.
H+ ; bicarbonate
Diarrhea causes (blank) to leave the stomach lumen, and (blank) to enter the blood.
bicarbonate; H+