Acid Base regulation

Question 1

Where does most of the acid come from within the body? What are the lesser sources?

Answer 1

Breakdown of metabolic products, producing CO2

Lesser = breakdown of proteins produces sulfuric/phosphoric acid

Question 2

What are the three acids that are only secreted through the kidneys?

Answer 2

1. Phosphoric acid
2. Sulfuric acid
3. Lactic acid

Question 3

What is the normal pH of the blood?

Answer 3

7.35-7.45

Question 4

What are the two major organs responsible for regulating blood pH? How long does each take to change the acidity of the blood?

Answer 4

Lungs- fast acting

Kidneys - slow acting

Question 5

What is the range of pH of urine? What does this depend on?

Answer 5

4.5- 8, depending on whether the kidney needs to excrete more acid or more base

Question 6

What is acidemia?

Answer 6

Blood pH <7.35

Question 7

What is acidosis?

Answer 7

Disease process or condition that acts to lower pH

Question 8

What is alkalemia?

Answer 8

Blood pH >7.45

Question 9

What is alkalosis?

Answer 9

Any disease process that raises pH

Question 10

What is severe acidosis?

Answer 10

Blood pH <7

Question 11

What is the highest pH that the body can tolerate?

Answer 11

8

Question 12

What part of the diet can contribute to alkalosis? How?

Answer 12

Fruits, since they contain the salts of weak organic acids (Na, and K)

Question 13

What is the immediate source of buffering changes in blood pH?

Answer 13

Body proteins (Hb)

Question 14

If the pH decreases, what is the response by the respiratory system?

Answer 14

Respiratory center of the brain will increase ventilation to blow off CO2, to decrease carbonic acid

Question 15

Respiratory acidosis is caused by what? (Hypoventilation or Hyperventilation?)

Answer 15

Hypoventilation

Question 16

Respiratory alkalosis is caused by what? (Hypoventilation or Hyperventilation?)

Answer 16

Hyperventilation

Question 17

Can metabolic acidosis/alkalosis be eliminated by respiratory compensation?

Answer 17

No, but can adjust

Question 18

If acidosis/alkalosis is nonrespiratory it is called what?

Answer 18

Metabolic

Question 19

How does the kidney compensate for metabolic alkalosis?

Answer 19

Excrete alkaline urine (HCO3)

Question 20

How does the kidney compensate for metabolic acidosis?

Answer 20

Excreting acidic urine, and reabsorb all of the bicarbonate in the filtrate

Question 21

What is a buffer?

Answer 21

A weak acid/base and its conjugate

Question 22

What is the Henderson-Hasselbalch equation?

Answer 22

pH = pka+log(base/acid)

Question 23

What is the equation for the bicarbonate buffer system? Walk through what would happen if [H] were to increase/decreases.

Answer 23

H2CO3 -> H +HCO3

If H increases, rxn shifts left

If H decreases, rxn shifts right

Question 24

A buffer system acts best around what pH?

Answer 24

where pH = pKa

Question 25

What is the buffer system used by the kidneys and intracellular fluid? What is its pKa?

Answer 25

Phosphate buffer system pKa = 6.8

Question 26

Why are proteins not part of the normal compensatory response to acid-base changes?

Answer 26

The amount of protein does not change in response to changes in the acid/base status of the body

Question 27

Why is Q the main AA involved in the ammonium buffer system?

Answer 27

can be broken down to HCO3 to go the the blood, and NH4 to the tubular lumen

Question 28

Where in the nephron is H+ secreted? (3) What is the mechanism behind this?

Answer 28

Proximal tubule, thick ascending tubule, and early distal tubule Na/H exchanger

Question 29

What happens to the H+ secreted into the tubular lumen?

Answer 29

Reacts with HCO3 to produce bicarb. Bicarb then converts to CO2 and H2O, and CO2 is picked up by the blood or converted to bicarb

Question 30

How do we "reabsorb" bicarb from the nephron?

Answer 30

Pump out H, take in H2O that that makes, and react it with water to produce bicarb

Question 31

For every H+ secreted into the tubular lumen, what happens?

Answer 31

a bicarbonate ion enters the blood

Question 32

How do we increase bicarb [c] if there is no more bicarb left in the tubular lumen?

Answer 32

Use carbonic anhydrase to convert CO2 in the blood to bicarb, and pump out H ion into the tubular lumen. Cl is used to follow this.

Question 33

What is the rxn that carbonic anhydrase catalyzes?

Answer 33

CO2 + H2O -> bicarb + H

Question 34

How does the hydrogen phosphate system work in the tubular cells?

Answer 34

Same way as CO2 is excreted, but more inert compound produced (NaH2PO4)

Question 35

What drives the dissociation of bicarb?

Answer 35

Drawing out H ions into the tubular lumen, which can be picked up by bicarb, phosphate, or excreted with Cl

Question 36

What if we have reabsorbed all the bicarbonate and used up all the phosphate buffers that can be excreted but are still acidotic? What is the next system utilized?

Answer 36

The glutamine- NH4+ system can be used for compensating for extreme acidotic condition

Question 37

What is the Q-NH4 system? Where does this take place in the nephron?

Answer 37

Q can be broken down into two bicarbs and two ammonium ions to be secreted into the urine This is found in the proximal tubule

Question 38

What is the process utilized later in the nephron to have the same effect as the Q-NH4 system?

Answer 38

ammonia is excreted to ensure urine is not too acidic

Question 39

What is secreted in the urine if the body needs to get rid of acid?

Answer 39

H+ and NH4

Question 40

What is secreted in the urine if the body needs to get rid of base?

Answer 40

HCO3

Question 41

How do the kidneys compensate for respiratory alkalosis? (hint, there is less CO2)

Answer 41

Reabsorb less bicarb; increase bicarb excretion

Question 42

What are the axes of the Davenport diagram?

Answer 42

``` X= pH Y= [HCO3] ```

Question 43

What happens to the davenport curve if you have an increase in baseline pCO2 (e.g. in COPD)

Answer 43

Shift up

Question 44

What happens to the davenport curve if you have an decrease in baseline pCO2?

Answer 44

Shifts down

Question 45

Short term changes are reflected how on the Davenport diagram?

Answer 45

Shifts **along** the respiratory curve

Question 46

Long term changes are reflected how on the Davenport diagram?

Answer 46

Shift of the metabolic curve

Question 47

Review that graph and situations!

Answer 47

Review that graph and situations!

Question 48

How do you differentiate between respiratory and metabolic acidosis in the clinic?

Answer 48

If change is due to pCO2, respiratory If change is due to HCO change, then it is metabolic

Question 49

What is the process of acid/base secretion used by the proximal tubules?

Answer 49

H/Na exchanger

Question 50

What is the process of acid/base secretion used by the collecting ducts?

Answer 50

H+ ATPase

Question 51

What are the two buffers in the urine that can absorb excess H+ from the blood?

Answer 51

Phosphate and ammonium buffers

Question 52

Where does the NH4 buffer come into play (proximal tubule or collecting duct)?

Answer 52

proximal tubule and thick limb

Question 53

What AA is used to generate 2 NH4 and 2 HCO3 for the ammonium buffer system?

Answer 53

Glutamine (Q)

Question 54

Is NH3 permeable to the cell membrane in the nephron? Is NH4?

Answer 54

NH3 is, but NH4 is not. Thus is hold H+ ions in the urine

Question 55

When is the glutamine budder utilized?

Answer 55

Under extreme acidemia

Question 56

What can hydrogen ions combine with (what are the buffers utilized)?

Answer 56

Cl PO3 HCO3 NH4 (from Q)

Question 57

Glutamine can be broken down into 2x(NH4 + HCO3). Where does each of these molecules go?

Answer 57

NH4 goes into lumen | HCO3 goes into the interstitium.