Role of the Kidneys in Acid/Base Balance Flashcards

1
Q

What is the molarity of [H+] at 7.40 pH?

A

0.00004 mmol/L

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2
Q

What is the difference between acidosis and acidemia?

A

Acidemia is the state of having more protons in the blood, while acidosis is the process of getting more acid in the blood.

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3
Q

How much metabolic acid is produced per day?

A

1 mmol/kg/day

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4
Q

__________ acids must be eliminated by the kidneys.

A

Nonvolatile

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5
Q

What two molecules often get metabolized to acidic compounds?

A

Nucleic acids (to phosphaturic acid) and sulfur-containing proteins

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6
Q

How much nonvolatile acid does the average Westerner consume per day?

A

60 - 70 mmol

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7
Q

List three general pH functions of the kidney.

A
Eliminate acid anions (sulfuric acid and phosphuric acid)
Reabsorb bicarb (~85% in the PCT)
Synthesize new bicarb (60 - 70 mmol daily; mainly in the intercalated cells of the DCT)
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8
Q

Essentially no bicarb synthesis can take place until _____________.

A

bicarb reabsorption is complete

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9
Q

How much HCO3 do we need to synthesize daily?

A

60 - 70 mmol

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10
Q

Impaired proximal-tubule resorption of bicarb will result in ____________.

A

proximal renal tubule acidosis

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11
Q

For every proton that is excreted, a new ________ is synthesized.

A

bicarb (this occurs because CO2 diffuses into the intercalated cells; carbonic anhydrase converts it to carbonic acid; a proton is excreted; and the remaining bicarb is reabsorbed)

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12
Q

What prevents the urinary pH from being so low?

A

Titratable acids (creatinine, phosphate, and urate) and ammonia trapping keep the pH from being lower than 4.5

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13
Q

NH3 diffuses easily through the _________.

A

apical membrane of the renal rubule

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14
Q

NH3 binds to ______ and becomes trapped as ______.

A

H+; NH4+

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15
Q

Ammonia is generated in the ___________ via ___________.

A

proximal tubule cells; glutaminase

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16
Q

One molecule of bicarb can bind to _____ protons.

A

two

17
Q

Acidosis stimulates the bones to ______________.

A

release buffers such as phosphate and carbonate

18
Q

How is bicarb different than other buffers?

A

Other buffers just bind H+ in the blood. Bicarb carries it into the tubule and to excretion.

19
Q

With chronic metabolic alkalosis, bicarb excretion can go to _________.

A

80 mmol per day (from the usual zero)

20
Q

How does hypokalemia lead to metabolic alkalosis?

A

Hypokalemia induces the intercalated cells to preferentially reabsorb K and secrete H+. More H+ secretion happens alongside bicarb synthesis.

21
Q

Hyperkalemia induces metabolic acidosis, but hyperkalemia also ____________, a counteractive effect.

A

induces increased bicarb synthesis

22
Q

How is bicarb absorbed in the proximal tubule?

A

By conversion to CO2. Carbonic anhydrase converts HCO3 and a proton to CO2 and water. The CO2 diffuses into the PCT cells, where it is converted to HCO3 and a proton. The proton is pumped back into the lumen (to participate in the carbonic anhydrase reaction again) and the bicarb is actively pumped into the interstitium with sodium.

23
Q

There are two membrane transporters that are crucial for secreting acid and synthesizing bicarb in intercalated cells. What are they?

A

On the apical side, there are ATP proton pumps that secrete protons. On the basolateral side, there are bicarb/chloride antiporters that allow for the reabsorption of chloride.