Gas Exchange

Question 1

What gasses, in what percents, compose air?

Answer 1

78.6% Nitrogen
20.9% Oxygen
0.04% Carbon dioxide
and trace gasses

Question 2

What is Dalton’s law?

Answer 2

The total atmospheric pressure is the sum of the partial pressures of all these individual gasses; all together equalling 760 mmHg

Question 3

What is Dalton’s law for partial pressures?

Answer 3

AND, the pressure exerted by each gas, it’s partial pressure, is directly proportional to the percentage of that gas in the gas mixture

Question 4

Per Dalton’s law, what is the partial pressure of O2 and N2 gasses in the atmosphere?

Answer 4

Nitrogen =	78.6% x 760 mmHg	= 597 mmHg
Oxygen=	20.9% x 760 mmHg	= 159 mmHg

Question 5

Why is the partial pressure of gases important in gas exchange?

Answer 5

Because they determine the rate of diffusion of gasses.

Question 6

_______ diffuses from the alveolar air into the capillary, and ________ ______ diffuses in the opposite direction, from the capillary into the alveoli.

Answer 6

oxygen

carbon dioxide

Question 7

What is the PO2 pressure in a lung alveolus? In a pulmonary capillary?

Answer 7

104 mmHg

40 mmHg

Question 8

What is the PCO2 pressure in a lung alveolus? In a pulmonary capillary?

Answer 8

40 mmHg

46 mmHg

Question 9

Gas exchange happens in ___ seconds, about __ of the time a RBC is in the pulmonary capillary.

Answer 9

.25

⅓

Question 10

How long does it take a RBC to pass through a pulmonary capillary?

Answer 10

.75 seconds

Question 11

Blood could travel __ faster through capillary and still by fully oxygenated

Answer 11

3x

Question 12

Why does CO2 have a smaller pressure gradient than O2 in the lungs?

Answer 12

CO2 is 20x more soluble in plasma and alveolar fluid, so CO2 diffuses more rapidly (easily), this is why CO2 has a smaller gradient.

Question 13

Why is PO2 104 and not 159 in the alveoli?

Answer 13

Airway humidifies air, changes pressure
Fresh air mixes with air in the lungs, therefore PO2 decreases
Air is already exchanging gases, continuous exchange decrease PO2

Question 14

When oxygen is transported, how, and in what percents?

Answer 14

1- Chemically bound to hemoglobin- 98%

2- Physically dissolved in plasma- 2%

Question 15

How is CO2 transported, and in what percents?

Answer 15

1- Loosely combined in the Hb molecule- 23%
2- Small amount dissolved in plasma- 7%
3- Most CO2 is converted in the RBC to bicarbonate ion- 70%

Question 16

In Hb, what is CO2 bound to?

Answer 16

The protein, not the Fe

Question 17

What are:
Hb
H2CO3

Answer 17

Hemoglobin

Carbonic acid

Question 18

What are:
HbO2
HCO3-

Answer 18

Oxyhemoglobin

Bicarbonate ion

Question 19

What are:
HbCO2
H+

Answer 19

carbaminohemoglobin

Hydrogen ion

Question 20

What is HHb?

Answer 20

Deoxyhemoglobin

Question 21

What is CAH? What does it do?

Answer 21

Carbonic anhydrase

CO2 + H20 → H2CO3

Question 22

What does H2CO3 disassociate into?

Answer 22

HC0-3 + H+

Bicarbonate and hydrogen ion

Question 23

What is the main formula for bicarbonate storage of CO2?

Answer 23

CO2 + H20 → (carbonic anhydrase) H2CO3 → (immediately dissociates) HC0-3 + H+

Question 24

What is chloride shift?

Answer 24

Cl- enters the RBC

HCO3- leaves

Question 25

How does Hb “buffer” H+?

Answer 25

Hemoglobin “buffers” the H+ ion and reduces the affinity of Hb for O2 and therefore promotes the unloading of O2

Question 26

Blood is slightly more _______ in lung capillaries, and slightly more ______ in tissue capillaries.

Answer 26

Alkaline

Acidic

Question 27

Why is blood slightly acidic in tissue capillaries?

Answer 27

Because excess H+ ions from RBCs make sblood slightly more acidic

Question 28

What does the carbonic acid-bicarbonate buffer system do?

Answer 28

It’s important in resisting shifts in blood pH

HCO3- acts as an “alkali reserve” when it diffuses out into the blood plasma