Gas Exchange and Transport

Question 1

What are the two types of flow?

Answer 1

• Convection (ventilatin)

- Diffusion

Question 2

What does Fick’s First law of diffuseion say?

Answer 2

The rate of diffusion over a semipermeable membrane is determined by:

• Surface area
• Concentration of substance
• Distance diffusion has to travel
• Diffusion coefficient

Question 3

What is a big variable that affects the partial pressure of oxygen as it enters the lungs?

Answer 3

-humidification of air

Question 4

What is the ratio of the rate of diffusion of oxygen to CO2 in a GAS?

Answer 4

1.2

ie, oxygen diffuses about 1.2 times more rapidly than CO2, as oxygen has a lower molecular weight.

Question 5

What determines a gas’s diffusion into a liquid?

Answer 5

• concentration of gas
• pressure of gas
• solubility of gas

Question 6

What determines the diffusion coefficient of a gas into a liquid?

Answer 6

• molecular weight

- solubility

Question 7

What is the ratio of diffusion of oxygen to CO2 in a LIQUID?

Answer 7

-CO2 is 22x more diffusible than O@, due to CO2’s greater solubility

Question 8

What are the three forms of gases in solution? Which forms contribute to a gas’s partial pressure in solution?

Answer 8

• Dissolved
• bound
• chemically modified

Only dissolved gases contribute to partial pressure

Question 9

What are the two types of limitations on gas exchange in the lungs?

Answer 9

• Diffusion limited

- Perfusion limited

Question 10

What is diffusion limited gas exchange?

Answer 10

• the limit of the total amount of gas transport by diffusion
• as long as there is a partial pressure gradient, diffusion continues along the capillary

Question 11

What is perfusion limited gas exchange?

Answer 11

• assumes diffusion occurs instantly and equilibrium is reached
• limitation here is that partial pressure gradient is not maintained if blood is not flowing

Question 12

Which type of limitation on gas exchange influence the diffusion of oxygen and CO2 the most?

Answer 12

• perfusion limitation

- oxygen HB molecules are usually fully loaded with O2 about 1/3 of the way through capillary

Question 13

What is Methemoglobin?

Answer 13

-hemoglobin where the iron moiety is in a ferric state (3+) so it cannot bind O2

Question 14

What is the O2 content of blood?

Answer 14

• the actual amount of O2 per volume of blood

- includes bound O2 and dissolved O2 (2%)

Question 15

Describe the Bohr Effect?

Answer 15

• increase in vessel pCO2 will decrease pH and shift O2 binding curve to right
• Decreases affinity of Hg for O2
• facilitates unloading of O2 in tissues

Question 16

What direction does increasing the temperature shift the O2 binding curve?

Answer 16

-to the right

Question 17

What direction does addition of 2,3-BPG shift the O2 binding curve?

Answer 17

-To the right

Question 18

What is the Haldane Effect?

Answer 18

-as O2 leaves Hb at the tissue level, there is an increase in the ability of Hb to carry CO2