Lecture 4: Gas Exchange

Question 1

what is pulmonary gas exchange?

Answer 1

diffusion of O2 from alveolar air into pulmonary blood

Question 2

CO2 moves from ____ to ___

Answer 2

pulmonary blood to alveolar air

Question 3

gases difuse down their ___ gradients

Answer 3

partial pressure

Question 4

what is systemic has exchange?

Answer 4

excahnge of O2 and Co2 between systemic capillaries and tissue cells

Question 5

the exchange of O2 and CO2 occurs via ___ diffusion

Answer 5

passive

Question 6

passive diffusion is governed by what 3 laws?

Answer 6

dalton, henry, Fick

Question 7

what is Dalton’s law?

Answer 7

the pressure exerted by each gas in a mixture is independent of the pressure exerted by other gases becasue the molecules are so far apart

Question 8

the pressure of each individiual gas is its ___ pressure

Answer 8

partial

Question 9

the total pressure of the mix of gases is the sum of ____

Answer 9

all the partial pressures

Question 10

what is atmospheric pressure?

Answer 10

760mmHg

Question 11

what is the partial pressure of humidified air? why is it lower than the atmospheric pressure?

Answer 11

500mmHg; because the partial pressure of water has to be subtracted

Question 12

____ law states that the amount of a gas that dissolves in a liquid is directly proportional to the partial pressure of the gas in which the liquid is in equilibrium

Answer 12

Henry’s

Question 13

what will happen to the difusion rate as long as Po2 in gas phase is higher than the Po2 in liquid?

Answer 13

there will be a net difusion of O2 into liquid

Question 14

the concetration of a gas is equal to the ___ and ___ of the gas

Answer 14

pressure and solubility

Question 15

the more soluble a gas, the ____ its concentration will be at any given pressure

Answer 15

greater

Question 16

transfer of gases across cell membranes and capillary walls occurs by diffusion, described by _____’s law

Answer 16

Fick

Question 17

Fick’s Law depends on what variables?

Answer 17

surface area, diffusion coeficient, partial pressure difference, thickness of membrane

Question 18

what are 3 important parameters for efficient gas exchange in the lungs?

Answer 18

1. partial pressure difference
2. large surface area
3. disatnce needs to be small

Question 19

what is the driving force of efficient gas exchange according to Fick’s Law?

Answer 19

partial pressure difference

Question 20

the diffusion coeficient for CO2 is ~ ____x greater than for O2

Answer 20

20

Question 21

when diffusion is decreased, is hypoxia or hypercapnia likely to happen first?

Answer 21

hypoxia

Question 22

the rate of O2 diffusing out of the alveoli is great enough that complete ____ is reached well before the blood reaches the end of the alveolar-capillary exchange unit

Answer 22

equilibrium

Question 23

if there is an abnormal alveolar diffusion barrier, this will impair diffusion and ____ will not be reached

Answer 23

equilibrium

Question 24

give 2 examples of conditions that impair alveolar diffusion, preventing equilibrium being reached

Answer 24

fibrosis and pulmonary edema

Question 25

when an alveolar-diffusion barrier such as fibrosis is present it is almost impossible to reach equilibrium when the barometric pressure ____

Answer 25

drops

Question 26

what are the 2 main parts of hemoglobin?

Answer 26

1. globin | 2. heme

Question 27

what is the structure of globin?

Answer 27

protein made of 4 polypeptide chains

Question 28

what is contained in the heme? what is its function>

Answer 28

Fe, carries O2

Question 29

how many O2 can be bound to 1 hemoglobin?

Answer 29

4

Question 30

O2 is not very soluble in water, and therefore also not in our blood, what is used to allow its transport in the body?

Answer 30

hemoglobin

Question 31

as Po2 increases, more O2 associates with ___

Answer 31

hemoglobin

Question 32

the oxygen-hemoglobin dissociation curve has what shape?

Answer 32

sigmoidal

Question 33

the oxygen hemoglobin dissociation curve is an example of ____ cooperativity

Answer 33

positive

Question 34

between 60-100mmHg the O2 hemoglobin curve hits a plateau. The hemoglobin is ___% saturated with O2. whay does this plateau exist?

Answer 34

90; safety feature, plateau allows pO2 to drop significantly before the effects are truly felt by hemoglobin

Question 35

the binding of O2 to hemoglobin is both ___ and fully ___

Answer 35

rapid; reversible

Question 36

what is P50 on the o2 hem curve?

Answer 36

Po2 where Hb is 50% saturated by O2

Question 37

changes in P50 reflect changes in hb's ____ for O2

Answer 37

affinity

Question 38

an increase in P50 means a ____ in Hbs affinity for O2 and vice versa

Answer 38

decrease

Question 39

the binding of the first O2 to Hb causes a ____ that makes it easier for the second O2 to bind and so on

Answer 39

conformational change

Question 40

a lower pH causes the affinity of Hb for O2 to ____

Answer 40

decrease

Question 41

a high blood Co2 causes the affinity of Hb for O2 to ___

Answer 41

decrease

Question 42

high temperature causes the affinity of Hb for O2 to ___

Answer 42

decrease

Question 43

addition of BPG/DPG causes the affinity of Hb for O2 to ___

Answer 43

decrease

Question 44

the affinity of Hb is often decreased by _____ hydrogen ionproduction

Answer 44

increased

Question 45

CO prevents the binding of ___ to ____

Answer 45

O2 to Hb

Question 46

CO has a ____x more affinity for Hb than O2

Answer 46

250

Question 47

cigarette smokers and those who live close to traffic polution have up to __% of their Hb bound to CO. What is the normal % of Hb boud to CO?

Answer 47

10; 1

Question 48

CO poisoning causes the O2 Hb curve to shift in what direction?

Answer 48

left

Question 49

CO poisoning _____ the affinity of HB for O2. what is the effect of this?

Answer 49

increases; Hb holds onto it and doesnt let it do its job

Question 50

in what 3 ways is CO2 carried in the blood?

Answer 50

1. dissolved 2. bound to carbamino compounds 3. in the form of bicarbonate

Question 51

the majority of CO2 is carried in the blood in what form ?

Answer 51

bicarbonate ions

Question 52

the enzyme used to make CO2 and H2o into carbonic acid is ____ and is only found in the _____

Answer 52

carbonic anhydrase; RBC (not plasma!)

Question 53

as blood picks up more Co2, the bicarbonate ions accumulate inside ____

Answer 53

RBC

Question 54

how can bicarbonate exit the RBC?

Answer 54

by exchanging for Cl (chloride shift)

Question 55

the ratio of sodium bicarbonate to carbonic acid is ___ . what is this vital to?

Answer 55

20 to 1 ; acid base balance

Question 56

as long as the ration remains at 20:1, the pH will remain at

Answer 56

7.4

Question 57

there is a balance between HCo3- governed by ___ and PCO2 governed by ___

Answer 57

renal excretion; ventilation

Question 58

if a person is hypoventilating or has a lung disease that prevents normal elimination of CO2, there is a ___ in arterial PCO2 and ___ in arterial H+ concentration. This is called respiratory ___

Answer 58

increase; increase; acidosis

Question 59

if a person is hyperventilating, there is a ___ in arterial CO2 and a ____ in arterial [h+]. This is called respiratory ___

Answer 59

decrease; decrease; alkalosis

Question 60

H+ in the RBC is buffered by ___

Answer 60

deoxyhemoglobin