Biochemical Ph Buffering

Front 1

Carbonic acid (H2CO3) has pKavalues of 3.8 & 10.2 while the amino acid histidine has pKavalues of 2.3, 6.0, & 9.6. Which compound, given equal concentrations, will best buffer the blood at a pH value of 7.4?
1.Carbonic acid
2.Histidine
3.Both equal
4.Neither able to buffer pH

Back 1

2. Histidine

Front 2

What is the optimal pH range for a buffer to resist changes in pH the best?

Back 2

At pH values 1 unit from the pKa value, the greater the resistance to changes in pH, the greater the capacity of the buffer system.

Front 3

What is the physiologic source of carbonic acid?

Back 3

CO2 + H2O -> H2CO3

Front 4

What catalyzes the conversion of CO2 and H2O to H2CO3?

Back 4

Carbonic anhydrase

Front 5

Which version of carbonic anhydrase is more important?

Back 5

Carbonic Anhydrase 2
*Carbonic anhydrase 1 deficiency has minimal consequences, CA2 deficiency yields osteopetrosis, renal tubular acidosis and cerebral calcification

Front 6

What kinds of drugs inhibit carbonic anhydrase?

Back 6

Diuretic drugs

Front 7

What are the effects of carbonic anhydrase inhibitors?

Back 7

1. lower blood [HCO3]
2. lower blood pH
3. lower blood lactate
4. increased ventilation

Front 8

What is the henderson-hasselbach equation for the bicarbonate blood buffer system?

Back 8

pH = 6.1 + log (([HCO3])/(.03PCO2))

Front 9

What is the normal physiologic concentration of HCO3?

Back 9

24mM

Front 10

What is the normal physiologic PCO2?

Back 10

40 mmHg

Front 11

What produces acid when you exercise?

Back 11

Cell metabolism

Front 12

Where is CO2 produced?

Back 12

In peripheral tissues by cell metabolism

Front 13

What form is most CO2 transported in during rest?

Back 13

bicarbonate (HCO3)

Front 14

Does the blood buffer CO2 equivalents?

Back 14

Nope, dissolved CO2 equivalents, however, buffer the pH

Front 15

What is acidemia?

Back 15

acidic blood pH (<7.35)

Front 16

What is acidosis?

Back 16

A disturbance leading to acidemia

Front 17

What is alkalemia?

Back 17

basic blood pH (>7.45)

Front 18

What is alkalosis?

Back 18

A disturbance leading to alkalemia

Front 19

What is metabolic acidosis?

Back 19

Lower [HCO3]
*ie: lactic acidosis

Front 20

What is metabolic alkalosis?

Back 20

higher [HCO3]
*ie: vomiting

Front 21

What is respiratory acidosis?

Back 21

higher pCO2
*ie: airway obstruction

Front 22

What is respiratory alkalosis?

Back 22

lower pCO2
*ie hyperventilation

Front 23

What are the most likely blood gas values shortly after initiating strenuous exercise?

 pH [HCO3]pCO2
1. 7.40 24 40
2. 7.50 30 40
3. 7.34 21 40
4. 7.50 24 32
5. 7.34 24 46

Back 23

5. 7.34 24 46

Front 24

A 24 year-old male is admitted to the emergency department unconscious and having difficulty breathing. The patient was discovered by his wife who called 911. The reported blood-gas values are [HCO3-] = 27 mM, pCO2= 65 mm Hg. What is the calculated blood pH?
1. 7.13
2. 7.24
3. 7.41
4. 7.56
5. 7.62
6. 7.76

Back 24

2. 7.24

Front 25

A 24 year-old male is unconscious and having difficulty breathing. The reported blood-gas values are [HCO3-] = 27 mM, pCO2= 65 mm Hg, pH = 7.26. The blood pressure = 120/80 mm Hg and heart rate = 85 bpm. What is the most likely source of the blood pH imbalance?
1.Heart attack
2.Partially blocked airway
3.Stroke
4.Severe dehydration

Back 25

2. Partially blocked airway

Front 26

What change does acute respiratory acidosis cause?

Back 26

Increased pCO2

Front 27

What can cause acute respiratory acidosis?

Back 27

1. Trauma to airway/lungs
2. Drugs like sedatives and general anesthetics
3. Head trauma -> causing slowed breathing
4. Poor mechanical respiration in ICU

Front 28

What effect on pCO2 does strenuous exercise have?

Back 28

Increases pCO2

Front 29

What is the physiologic response to high CO2?

Back 29

Increased minute ventilation

Front 30

When does the pH = pKa?

Back 30

When the concentrations of acid and base are equal

Front 31

What is the difference in concentration of CO2 in the lungs verses the atmosphere?

Back 31

The pCO2 of the lungs is much higher than the pCO2 of the atmosphere.

Front 32

What facilitates the ability of CO2(g) to be in equilibrium w/ CO2(aq)?

Back 32

The large surface area of the lungs

Front 33

A 16 year-old high school football player was briefly knocked unconscious and sent to hospital as a precaution. In route, he passed out. On admission, the respiration rate = 30 bpm, arterial pO2= 95 mm Hg, pCO2= 20 mm Hg, and [HCO3-] = 20 mM. What is the arterial blood pH?
1. 7.13
2. 7.24
3. 7.41
4. 7.56
5. 7.62
6. 7.76

Back 33

5. 7.62

Front 34

What causes acute respiratory alkalosis?

Back 34

1. hyperventilation
2. Drugs
3. head trauma -> causing hyperventilation
4. poor mechanical respiration in ICU

Front 35

What change in [HCO3] is seen for every 10 mmHg increase in pCO2?

Back 35

HCO3 increases 1 mM for every 10 mmHg increase in pCO2 due to chemical equilibrium

Front 36

What change in [HCO3] is seen for every 1 mmHg drop in pCO2?

Back 36

0.2mM HCO3 decrease for every 1 mmHg drop in pCO2

Front 37

Why does a hyperventilation increase pH?

Back 37

Fast breathing expels CO2.
-pCO2 is less than normal
-pH increases

Front 38

IF there is an acute change that causes [HCO3] to rise or drop, what organ compensates?

Back 38

Kidneys

Front 39

If there is an acute change that causes pCO2 to rise or drop, what organ compensates?

Back 39

Lungs

Front 40

Why can pH differ significantly b/e the venous and arterial sides of circulation?

Back 40

pCO2 can differ b/e the two sides significantly, thus pH can differ significantly.