Acid-Base Balance Part 1

Question 1

What is the Henderson-Hasselbach equation

Answer 1

ph = pK + log [ (HCO3/H2CO3) ]

Question 2

what is the ratio of bicarbonate (salt) to carbonic acid (acid) which results in a normal pH of 7.40

Answer 2

20 : 1

Question 3

What is the equation which describes the bicarbonate-carbonic acid system

Answer 3

CO2 + H20 H2CO3 H+ + HCO3-

Question 4

what enzyme catalyzes the reversible reaction in the equilibrium equation?

Answer 4

Carbonic anhydrase

Question 5

What two cell types contain carbonic anhydrase

Answer 5

RBC’s and renal epithelial cells only

Question 6

What is the modified Henderson-hasselbach equation as used in the bicarbonate:carbonic acid buffer system

Answer 6

pH = pK + log [ HCO3/ (alpha) (pCO2) ]

Question 7

What are the values for pK in the blood and alpha, the solubility coefficient

Answer 7

pK = 6.1
alpha = 0.031

Question 8

Two reasons why hemoglobin is an important whole blood buffer, regulating acid-base balance both in the lungs and the tissues

Answer 8

1. RBC’s contain carbonic anhydrase (enzyme that converts the three forms of carbon dioxide)
2. Has 9 histidine residues on each of its four chains that can accept carbon dioxide molecules forming stable amide bond

Question 9

Physiologic importance of the isohydric shift in red blood cells

Answer 9

It is important because it is a set of chemical reactions by which oxygen is released to the tissues and carbon dioxide is taken up WHILE the blood remains at a constant pH

Question 10

Process of the isohydric shift in red blood cells

Answer 10

• CO2 is generated from metabolism
• it joins with water to become H2CO3 (by carbonic anhydrase)
• It then splits to become an H+ ion and HCO3-
• H ion attaches to hemoglobin to become reduced hemoglobin
• when that happens, oxygen is given to the tissues

Question 11

Chloride shift:

- movemnt of bicarbonate and chloride

Answer 11

**bicarb goes out of the cell and Cl- goes into the cell

Question 12

Chloride shift:
- how this shift is responsible for the hyper-or hypochloremia noted in acid-bace disturbances for which the body is compensating

Answer 12

*This regulates how much Cl- is getting into the cell so if its to low then its hypochloremia

Question 13

*

Answer 13

*

Question 14

Protein and phosphate buffer system according to specific sites of action (blood,tissue, and/or organs)

Answer 14

Protein Buffer system: 2/3 buffering power in blood and most of the buffering power intracellularly
Phosphate Buffer system: minor component of blood but great importance in the kidneys and RBC’s

Question 15

Protein and phosphate buffer system according to processes involved

Answer 15

Protein: it accepts hydrogen ions because of its histidine residues
Phosphate: hydrogen ions are added to filtrate in the forming urine. Dibasic phosphate picks up a hydrogen ion to become monobasic

Question 16

Rank the body’s buffer systems in order of their importance

Answer 16

Whole blood: Hemoglobin is most important

Plasma: Bicarbonate most important, then protein, then phosphate

Question 17

State the organ which regulates the respiratory component and the organ which regulates the metabolic component of acid-base balance

Answer 17

Respiratory: lungs
Metabolic: kidneys

Question 18

Pulmonary hyperventilation:
- how does it regulate the acid-base balance according to how it alters the bicarbonate:carbonic acid ratio, thus compensating for acidosis or alkalosis

Answer 18

Hyperventilation increases CO2 release, decreasing the denominator in of the H-H equation

Question 19

Pulmonary hypoventilation:
– how does it regulate the acid-base balance according to how it alters the bicarbonate:carbonic acid ratio, thus compensating for acidosis or alkalosis

Answer 19

Hypoventilation decreases CO2 release, increasing the denominator of the H-H equation

Question 20

Four specific mechanisms by which the kidney regulates acid-base balance

Answer 20

1. Reabsorption of bicarbonate
2. Excreting excess H+ by exchanging Na+ for H+
3. Forming titratable acids with phosphate
4. Excreting excess H+ as NH4+

Question 21

Reabsorption of bicarbonate

- How does it correct for acidosis or alkalosis

Answer 21

In filtrate:
HCO3 in filtrate + H ions from renal cells form carbonic acid (H2CO3), this breaks down into H2O and CO2 which enter the renal tubular cells
In renal cells:
H2O and CO2 come together to form H2CO3. This breaks down into H+ ion and HCO3-. Bicarb goes into the interstitial fluid

Question 22

Excreting excess H+ by exchanging Na+ for H+

- How does it correct for acidosis or alkalosis

Answer 22

In renal cells:

H2CO3 (carbonic acid) breaks down into H+ ion and bicarbonate. H+ ions are exchanged (out) for a sodium (in)

Question 23

Forming titratable acids with phosphate

- How does it correct for acidosis or alkalosis

Answer 23

IN filtrate:

NaHPO4 joins with the secreted H ion to form NaH2PO4 which is a titratable acid that is excreted in the urine

Question 24

Excreting excess H+ as NH4+

- How does it correct for acidosis or alkalosis

Answer 24

H ion plus NH3 are secreted by the renal cells. They come together to form NH4+ which is excreted in the urine

Question 25

How does the kidney excrete acid via sodium hydrogen ion exchange?

Answer 25

*

Question 26

How does the kidney excrete acid via sodium hydrogen ion exchange including
- How mechanism maintains the Gibbs-Donnan equilibrium

Answer 26

*

Question 27

How does the kidney excrete acid via sodium hydrogen ion exchange including
- Interrelationship of hydrogen, sodium, and potassium ions’ reabsorption and secretion

Answer 27

*

Question 28

How does the kidney excrete acid via sodium hydrogen ion exchange including
- The reabsorption of bicarbonate when sodium is reabsorbed

Answer 28

*