Lecture 19 - Renal Acid-Base Flashcards
This is an acid excreted from the lungs. What is an example?
volatile acid; carbon dixoide
This substance receives H+ ions
A. acid
B. base
C. Volatile compound
D. Non-volatile compound
B. base
This is the classification of acids excreted from kidneys. What is it called? Give an example.
Non-volatile (or “fixed”) acid; sulphuric acid, phosphoric acid, ketoacids
-log[H]+
A. pKa
B. pKb
C. pH
D. pOH
C. pH
What is the normal pH of arterial blood?
A. 7.37-7.44
B. 7.35-7.45
A. 7.37-7.44
What is the KEq?
The dissociation constant for a given reaction. It is the ([product]/[reactant])
What is the normal pH range for venous blood?
A. 7.37-7.44
B. 7.35-7.45
B. 7.35-7.45
This compound dissociates to release H+
A. Acid
B. Base
C. Volatile chemical
D. Non-volatile chemical
A. Acid
These are capable of reversibly binding H+
A. Acid
B. Base
C. Buffer
D. Hydroxide ions
C. buffer
What are the components of the bicarbonate buffer system?
weak acid;
bicarbonate salt
In the bicarbonate buffer system, the strength of the product is (proprtional/inversely proportional) to the strength of the added reactant.
Inversely proportional;
Example: the addition of a strong acid forms a weak acid. This is how the buffer system works. Strong acids produce weak acids, which do not readily dissociate. These weak acids “trap” H+, and prevent large changes in pH
The most important ECF buffer system is the:
a. Protein buffer system
b. Bicarbonate buffer system
c. Phosphate buffer system
b. Bicarbonate buffer system
Increased [H+] in the bicarbonate buffer system results in increased _____ via carbonic anhydrase. How is this product excreted?
CO2;
by increasing the respiratory rate
Metabolic acid-base disorders are the result of __________.
changes to [HCO3]
Respiratory acid-base disorders are the result of _________.
changes to [H+], typically due to a respiratory problem.
The most important renal tubular fluid buffer system is the:
a. Protein buffer system
b. Bicarbonate buffer system
c. Phosphate buffer system
c. Phosphate buffer system
The primary method for removal of non-volatile acids is through ___________.
renal excretion
Reabsorption of HCO3 requires the HCO3 to react with ____ prior.
A. H+
B. H20
C. CO2
D. Na+
A. H+
What are the 3 mechanisms of ECF [H+] regulation?
1) Reabsorption of filtered HCO3
2) Secretion of H+
3) Production of new HCO3
Where in the kidney tubules does H+ ion secretion occur?
Secondary active transport - everywhere except thin asc./desc. Loops of Henle
Primary - late distal tubule’s intercalated cells
Where in the kidney tubules does bicarbonate reabsorption occur?
PCT
Describe the mechanism by which bicarbonate ion is reabsorbed.
Bicarbonate is filtered at the glomerulus, and H+ is secreted by tubular cells. These combine to form carbonic acid, which dissociates into water and carbon dioxide.
The CO2 diffuses into the tubular cells and combines again with water, forming carbonic acid again.
This carbonic acid then dissociates into HCO3 and H+.
The HCO3 then diffuses across the basolateral membrane and back into blood.
What is the function of carbonic anhydrase?
To form carbonic acid in tubular cells.
Is the HCO3 in the ECF the same as the HCO3 filtered at the glomerulus? Why or why not?
No. The HCO3 that is reabsorbed into the blood arises from the dissociation of the H2CO3 formed by carbonic anhydrase in the tubular cell.
Describe what is meant by “incomplete titration.”
Incomplete titration occurs when there is not a 1:1 ratio of H+:HCO3 excretion. Instead, HCO3 can be reabsorbed to correct acidosis (completing the titration). Or, HCO3 can be excreted in the urine to correct metabolic alkalosis.
Intercalated cells can secrete H+ ions into the tubular lumen via ____.
a. primary active transport
b. secondary active transport
a. primary active transport
H+ ATPase pumps act to remove hydrogen following carbonic acid dissociation in tubular epithelial cells. Where are these H+ ATPases located?
A. PCT
B. Loop of Henle
C. Intercalated cells - late DCT
D. Principal cells - late DCT
C. Intercalated cells - late DCT
H+ can also be removed by Na/H+ counter transport. Where does this occur?
A. PCT
B. Loop of Henle
C. Intercalated cells - late DCT
D. Principal cells - late DCT
A. PCT
What is the lower limit of pH that the kidneys can achieve?
A. 4.0
B. 4.5
C. 5.0
D. 5.5
B. 4.5
Excess H+ generation primarily occurs through:
A. failure to completely titrate H+ to HCO3
B. through protein metabolism
C. through improperly functioning phosphate buffer system
B. through protein metabolism
Why can only a small amount of free H+ be excreted in urine daily?
In order to excrete all free H+, urine output would have to increase dramatically (to approximately 2,667 L/day)
What two buffer systems play an important role in the excretion of large amounts of H+?
Phosphate and ammonia buffer system
How do phosphate and ammonia buffer systems generate “new” bicarbonate?
The excess H+ is bound to phosphate and ammonia buffer systems. Therefore, HCO3 remains unbound and free in the system. That HCO3 then is returned to the blood, generating “new” HCO3.
Excess base is handled by increased HCO3 excretion. By what mechanism does this occur?
By failing to resorb excess base.
