Renal Acid Base Regulation Flashcards
1
Q
Acids are compounds that release
A
H+ ions
2
Q
_____ dissociate completely
A
Strong Acids
3
Q
_____ do not dissociate completely and dissociate into hydrogen ions (H+) and conjugate base
A
Weak acids (conjugate acid)
4
Q
Compounds that accept H+ ions
A
Bases
5
Q
What are the two types of acids produced in the body
A
- Volatile Acids
- Nonvolatile Acids (fixed acids)
6
Q
Volatile acid are excreted from the ____
A
lungs
7
Q
Carbon dioxide is a _____ acid
A
Volatile
8
Q
Carbon dioxide is a product of
A
cellular aerobic metabolism
9
Q
CO2 + H2O —->
A
H2CO3
10
Q
H2CO3 —->
A
H+ + HCO3-
11
Q
Carbonic anhydrase catalyzes
A
H2O + CO2—-> H2CO3
and
H2CO3—–> HCO3- + H+
12
Q
Nonvolatile acids (fixed acids) are excreted from
A
kidneys
13
Q
Examples of Nonvolatile acids (fixed acids)
A
- Sulfuric acid (product of protein catabolism)
- Phosphoric acid (product of phospholipid catabolism)
- Ketoacids, lactic acid, salicylic acid
14
Q
sulfuric acid is a product of
A
protein catabolism
15
Q
Phosphoric acid is a product of
A
phospholipid catabolism
16
Q
pH=
A
pH= -log{H+}
17
Q
Arterial blood pH range
A
7.37-7.44
18
Q
Venous blood pH range
A
7.35-7.45
19
Q
The greater the hydrogen ion concentration, the ____ the pH
A
Lower
20
Q
____ is the equilibrium constant for the dissociation reaction
A
Ka
21
Q
The major systems regulating [H+]
A
- Chemical acid-base systems of the body fluid
- Respiratory center
- Kidneys
22
Q
Henderson-Hasselbalch Equation
A
pH= pKa + log [A-]/ [HA]
23
Q
A _____ is a substance that can reversibly bind H+
A
buffer
24
Q
a buffer consists of a
A
weak acid (HA)=conjugate acid
25
What are the 3 buffer systems
- bicarbonate buffer system
- Phosphate buffer system
- proteins as buffer
26
Bicarbonate buffer system consists of
- a weak acid: H2CO3
| - A bicarbonate salt: NaHCO3
27
CO2+H2o----> H2CO3 is catalyzed by
carbonic anhydrase
28
when a strong acid is added to the bicarbonate buffer system _____ is formed
a weak acid
ex. H+ + HCO3- ----> CO2 +H2O
29
Addition of a strong base to bicarbonate buffer system leads to the formation of
a weak base
- NaOH+ H2CO3----> NaHCO3 + H2O
30
The increased levels of HCO3- can be excreted via the
kidneys
31
What is the most important extracellular buffer system
Bicarbonate Buffer System
32
Bicarbonate concentration is regulated mainly by the
kidneys
33
pCO2 is controlled by rate of
respiration
34
a pH of ____ occurs when concentrations of both bicarbonate ions and carbon dioxide are equal
6.1 ( note that at this point pH= pKa of the buffer system)
35
Plays a major role in buffering renal tubular fluid and intracellular fluids
Phosphate Buffer system
36
What are the two reasons for phosphate buffer systems importance as a buffer in kidney tubular fluids
- Usually becomes greatly concentrated in tubules
| - Lower pH of the tubular fluid brings the operating range of the buffer closer to the pK of the buffer system
37
What are the main elements of the phosphate buffer system
H2PO4- , HPO4
38
In the phosphate buffer system strong acids is replaced by
an additional amount of weak acid and pH change is minimal
39
kidneys can excrete either acidic or basic urine how
- Large numbers of bicarbonate ions are filtered continuously into the tubule, and if they are excreted this removes base form the blood
- Large numbers of hydrogen ions can be secreted into the tubular lumen
40
The primary method for removing nonvolatile acids is through
renal excretion
41
Almost all filtered bicarbonate is ______, but it must react with secreted hydrogen ion to form _____ before it can be _______.
reabsorbed, carbonic acid, reabsorbed
42
_____ mEq of hydrogen ion must be secreted each day just to reabsorb the ______ mEq of filtered bicarbonate
4320mEq, 4320 mEq
43
Mechanisms for regulating extracellular H+
- kidneys reabsorb filtered bicarbonate ions
- kidneys can secrete hydrogen ions
- Kidneys produce new bicarbonate ions
44
What percent of bicarbonate is reabsorbed in the proximal convoluted tubule
85%
45
What % of bicarbonate is reabsorbed in the thick ascending loop of Henle
10%
46
What percent of bicarbonate is reabsorbed in the distal tubule and collecting duct
about 4.9%
47
Explain the mechanism of Bicarbonate reabsorption in the proximal, thick ascending, and early distal tubule
Secondary active transport via H+-Na antiporter
The secretory process begins when CO 2 either diffuses into the tubular cells or is formed by metabolism in the tubular epithelial cells. CO 2 , under the influence of the enzyme carbonic anhydrase, combines with H 2 O to form H 2 CO 3 , which dissociates into HCO 3 − and H + . The H + is secreted from the cell into the tubular lumen by sodium-hydrogen counter-transport. That is, when Na + moves from the lumen of the tubule to the interior of the cell, it first combines with a carrier protein in the luminal border of the cell membrane; at the same time, a H + in the interior of the cells combines with the carrier protein. The Na + moves into the cell down a concentration gradient that has been established by the sodium-potassium ATPase pump in the basolateral membrane. The gradient for Na + movement into the cell then provides the energy for moving H + in the opposite direction from the interior of the cell to the tubular lumen. The HCO 3 − generated in the cell (when H + dissociates from H 2 CO 3 ) then moves downhill across the basolateral membrane into the renal interstitial fluid and the peritubular capillary blood. The net result is that for every H + secreted into the tubular lumen, an HCO 3 − enters the blood.
48
How is H+ secreted in the late distal and collecting tubules
Primary active secretion of H+ in the intercalated cells
It occurs at the luminal surface of the tubular cells, where H+ is transported directly by specific proteins, a hydrogen-transporting ATPase and a hydrogen potassium-ATPase transporter
Hydrogen ion secretion is accomplished in two steps
- 1.) the dissolved CO2 in this cell combines with H2O to form H2CO3
- 2.) The H2CO3 then dissociates into HCO3-, which is reabsorbed into the blood, plus H+, which is secreted into the tubule by means of the hydrogen-ATPase transporters.
note that one HCO3- is absorbed for each H+ secreted,and one chloride ion is passively secreted along with H+
49
Although the secretion of H+ in the late distal tubule and collecting tubules accounts for only about 5 percent of the total H+ secreted, this mechanism is important in
forming maximally acidic urine
50
What is the transporter in Type A intercalated cells that allows HCO3- to enter the renal interstitial fluid
HCO3- - Chloride exchanger
51
Where in the kidney tubules does hydrogen ion secretion and bicarbonate reabsorption occur
- Hydrogen ion secretion via secondary active transport (coupled with sodium ion transport) occurs in almost all parts of the tubules except the descending and ascending thin limbs of the loop of henle
- Primary active hydrogen secretion begins in the late distal tubules in the intercalated cells and involves a hydrogen-transporting ATPase and Hydrogen-potassium ATPase transporter
52
Primary active hydrogen secretion begins in the ____ and involves a ______ and ______
Late distal tubules in intercalated cells,hydrogen-transporting ATPase and hydrogen-potassium ATPase transporter
53
Bicarbonate reabsorption is initiated by a reaction in the tubules between bicarbonate ion filtered at the glomerulus and hydrogen ion secreted by the _____. This results in the formation of ______ which then dissociates into carbon dioxide and water
tubular cells, Carbonic acid
54
Carbon dioxide diffuses into the tubular cells where it recombines with water to generate a new ______ which then dissociates to form ____ and ____
Carbonic acid molecule, bicarbonate ion, hydrogen ion
55
The bicarbonate ion diffuses through the basolateral membrane into the ______ fluid and then into the ___
interstitial fluid, blood
56
______ is necessary for the formation of carbonic acid from carbon dioxide and water
Carbonic anhydrase
57
The bicarbonate ion taken up by the pericapillary tubules is formed from the dissociation of _______ into hydrogenion and bicarbonate ion.
carbonic acid
58
Is the bicarbonate ion taken up by the pericapillary tubules the same as the one that is filtered into the tubular lumen
No
59
Explain the use of incomplete titration to correct acidosis or alkalosis
- Normally each time a hydrogen ion is formed in the tubular epithelial cells, a bicarbonate ion is also formed and released back into the blood
- In metabolic acidosis new bicarbonate ion is added to the extracellular fluid
- in metabolic alkalosis, bicarbonate ions are removed form extracellular fluid by renal excretion
60
Active transport resulting in hydrogen ion secretion is carried out by
intercalated cells
61
2-step process of hydrogen ion secretion in intercalated cells
- Dissolved carbon dioxide in intercalated cells combines with water to form carbonic acid
- The carbonic acid then dissociates into bicarbonate, which is rapidly reabsorbed into the blood, and hydrogen ion, which is secreted into the tubular lumen by means of the hydrogen-ATPase transporters
62
What is the lower limit of pH that can be achieved in normal kidneys
4.5
63
Hydrogen ion secretion in the proximal tubule (and other areas of the renal tubule) occurs via __________
secondary sodium-hydrogen countertransporter
64
The sodium-hydrogen exchangers are located on the _________ of the renal epithelial cells
apical (luminal) membranes
65
Sodium-potassium ATPase exchangers are found on the ________ of renal epithelial cells
basal membranes
66
Each day the body produces about _____ mEq of nonvolatile acids, mostly from the metabolism of proteins. because these are nonvolatile acids, they cannot be excreted by the _____. They are primarily removed via ______
80mEq, Lungs, They are primarily removed via renal excretion
67
The loss of bicarbonate ions in the extracellular fluid is the same as
adding hydrogen ions to the Extracellular fluid
68
Only a small part of the excess hydrogen ion secreted in excess of the filtered bicarbonate ion can be excreted in ionic form in the ____
urine
69
why can only a small part of the excess hydrogen ion secreted in excess of the filtered bicarbonate ion be excreted in ionic form in the urine
Because the minimal urine pH is about 4.5 (H+ concentration= 10^-4.5 mEq/L or 0.03 mEq/L)
70
To excrete the 80mEQ of nonvolatile acid formed by metabolism per day, about _____ liters of urine would have to be excreted if all the excess hydrogen ion remained free in solution
2667 (80/minimal urine pH, which is equal to 0.03mEq/L of H+)
71
What buffers are important in allowing larger amounts of hydrogen ion to be excreted
- Phosphate buffer system
| - Ammonia buffer system
72
excess hydrogen ions are eliminated through binding with _____ or _____ ions
phosphate or ammonia
73
What is new bicarbonate ion
when hydrogen ions are combining with other buffers in the tubular lumen, then excess bicarbonate ion is available to be returned to the blood. This is new bicarbonate ion
74
Where are intercalated cells found
Only in the late distal tubules
75
What are intercalated cells role in hydrogen ion transport
They actively transport Hydrogen ions into the tubular lumen using hydrogen ATPase transporters.
This leads to the acidic concentration of urine
76
Reduction in extracellular fluid hydrogen ion concentration leads to
alkalosis
77
Kidneys can correct ____ by failing to reabsorb all the filtered bicarbonate ion (this is the same as adding hydrogen ion to the extracellular fluid)
alkalosis
78
kidneys can correct alkalosis by
failing to reabsorb all the filtered bicarbonate ion (this is the same as adding hydrogen ion to the extracellular fluid)
79
_____ occurs when the ratio of bicarbonate ion to carbon dioxide n extracellular fluid decreases
Acidosis
80
Metabolic acidosis
Decrease in bicarbonate ion
81
Respiratory acidosis
Increase in carbon dioxide
82
What is the primary compensatory response for respiratory acidosis
increase in plasma bicarbonate ion due to addition of new bicarbonate by the kidney
83
Primary compensatory response metabolic acidosis
- Increased ventilation rate
| - Renal compensation: adds new bicarbonate ion to extracellular fluid
84
Respiratory alkalosis occurs when there is a decrease in
carbon dioxide concentration
85
Respiratory alkalosis can be caused by
- caused by hyperventilation
86
Compensatory response of respiratory alkalosis
-Reduction in plasma bicarbonate ion concentration caused by renal excretion of bicarbonate ion
87
Metabolic alkalosis is caused by a rise
extracellular fluid bicarbonate ion concentration
88
What are the compensatory response for metabolic alkalosis
- Decreased ventilation
| - Increased renal bicarbonate ion excretion
89
What is the most important buffering system for renal tubular fluid
Phosphate buffer system
90
Compounds that dissociate incompletely into hydrogen ions and a conjugate base are made of compounds
- Weak acids
91
The bicarbonate buffer system consists of bicarbonate and what
A weak acid
92
Primary active hydrogen secretion involves a hydrogen transporting ATPase. It occurs in which of the following parts of the renal tubules?
- A.) Descending limb of Henle
- B.) Ascending limb of Henle
- C.) Late distal tubules in intercalated cells
- D.) Early collecting in principle cells
C.) Late distal tubules in intercalated cells
93
Most bicarbonate reabsorption occurs in which of the following parts of the renal tubule?
A.) Proximal tubule
B.) Descending limb of Henle
C.) Ascending limb of Henle
D.) Distal tubule
- Proximal Tubule
94
Which of the following occurs when a decrease in bicarbonate ion results in a decrease in the ratio of bicarbonate ion to carbon dioxide in the extracellular fluid?
A.) Respiratory Acidosis
B.) Respiratory Alkalosis
C.) Metabolic Acidosis
D.) Metabolic Alkalosis
Metabolic Acidosis
95
Respiratory alkalosis due to a decrease in carbon dioxide concentration caused by hyperventilation is compensated for by which of the following mechanisms?
A.) Increased Ventilation Rate
B.) Decreased Ventilation Rate
C.) Renal Excretion of bicarbonate ion
D.) Renal addition of new bicarbonate ion to extracellular fluid
C.) Renal excretion of bicarbonate ion
