23.5 pysical properties of gas exchange

Question 1

diffusion of gases through the respiratory membrane depends on 4 things. what are they?

Answer 1

membrane thickness
diffusion coefficient of gasses (how easily a gas diffuses through a liquid or tissue)
surface area
partial pressure difference

Question 2

how does membrane thickness affect the diffusion rate of gases?

Answer 2

the thicker the membrane, the slower the diffusion rate

Question 3

what is the diffusion coefficient of a gas?

Answer 3

how easily a gas diffuses through a liquid or tissue

Question 4

which is more diffusable, CO_2 or O_2?

Answer 4

CO_2 is 20x more diffusable than O_2

Question 5

what affects the diffusion coefficient of a gas?

Answer 5

surface areas of the membrane (damage)

partial pressure of gases in alveoli and bl

Question 6

what can affect the surface area of the lungs?

Answer 6

diseases like emphysema and lung cancer can decrease the available surface area

Question 7

how do partial pressure differences affect gas exchange?

Answer 7

gases move from areas of high partial pressure to areas of low partial pressure

Question 8

what is the total pressure of the atmosphere (at sea level)?

Answer 8

760 mmHg

Question 9

what is partial pressure?

Answer 9

the pressure exerted by each type of gas in a mixture

Question 10

in a mixture of gases, the percentage of each gas is proportionate to its _________

Answer 10

partial pressure

Question 11

what is H_2O vapor pressure?

Answer 11

pressure exerted by gaseous H_2O in a mixture of gases

Question 12

what does air in the resp system contain humidity?

Answer 12

mucous linings of the system

Question 13

what determines the [ ] of a gas in a liquid?

Answer 13

its partial pressure + solubility coefficient

Question 14

draw the simple gas exchange picture

Answer 14

DO IT

Question 15

how is O_2 transported?

Answer 15

98. 5% is dissolved in plasma

1. 5% dissolved in plasma

Question 16

what does the O_2-Hgb dissociation curve describe?

Answer 16

the % of Hgb fully saturated with O_2 at any given PO_2

Question 17

what does the O_2-Hgb dissociation curve show about O_2 saturation at rest?

Answer 17

that Hgb is almost completely saturated with O_2 when PO_2 is 80 mmHg or higher. At lower PO_2, the O_2 dissociates from Hgb

Question 18

draw the O_2-Hgb dissociation curve

Answer 18

DO IT

Question 19

what is the environment of the tissue vs that of the lungs in regards to the O_2-Hgb dissociation curve?

Answer 19

TISSUE
lower pH 7.0 ish (more acidic)
increased CO_2 
increased Temp
LUNGS
higher pH
lower CO_2
lower Temp

Question 20

how do the tissues favor Hgb unbinding (dissociating)?

Answer 20

lower pH 7.0 ish (more acidic)
increased CO_2
increased Temp

Question 21

how do the lungs favor Hgb binding?

Answer 21

higher pH
lower CO_2
lower Temp

Question 22

which direction does the O_2-Hgb dissociation curve move in an environment that is low in pH, high in CO_2, and high in temp?

Answer 22

to the right (Hgb becomes “fully” saturated only at higher PO_2

Question 23

how much O_2 is released to the tissues at rest?

Answer 23

23%

Question 24

how is CO_2 transported?

Answer 24

70% as bicarbonate ions
23% bound to Hgb
7% in sol’n with plasma

Question 25

when does Hgb bind more readily to CO_2?

Answer 25

when the Hgb has released its O_2

Question 26

give the CO_2 to bicarbonate ion (HCO_3^-) rxn

Where does this take place?

Answer 26

CO_2 + H_2O <> H_2CO_3 <> H^+ + HCO_3
maybe write it on paper
arrows to the R happen at the tissue level
arrows to the L happen at alveoli

Question 27

describe the Chloride shift

Answer 27

at the tissue capillaries: as CO_2 enters RBC, it reacts with H_2O to form HCO_3^- and H^+ ions
Cl^- ions enter the RBC as HCO_3^- leaves (balance of ion mvmt)

Question 28

what happens to the H+ ions after they split from carbonic acid (H_2CO_3) to form H^+ and bicarbonate (HCO_3^-)?

Answer 28

H^+ ions combine with Hgb

Question 29

what promotes the conversion of CO_2 to HCO_3^-?

Answer 29

HCO_3^- leaving the cell
and
H^+ binding to the Hgb

Question 30

what does CO_2 react with to form H_2CO_3?

Answer 30

H_2O and carbonic anhydrase

Question 31

what is H_2CO_3?

Answer 31

carbonic acid

Question 32

what is HCO_3^-?

Answer 32

bicarbonate ion

Question 33

explain what happens with CO_2 transport at the pulmonary capillaries

Answer 33

CO_2 leaves RBCs, which results in the formation of additional CO_2 from carbonic acid (H_2CO_3)
bicarbonate ions are exchanged for Cl^- and the H^+ ions are released from the Hgb
release of the H^+ from Hgb means O_2 can bind at the alveolus, exactly where the conditions favor it (more basic pH, lower Temp, lower CO_2)

Question 34

how does the resp system regulate bl pH?

Answer 34

increased plasma CO_2 levels lower bl pH bc as plasma CO_2 increases, so do H^+ levels, which decreases the pH (more acidic, more H^+)

Question 35

how does ventilation rate affect plasma CO_2 levels?

Answer 35

hyperventilation decreases plasma CO_2 levels

hypoventilation increases plasma CO_2 levels

Question 36

what is the Bohr effect?

Answer 36

the effect of pH on the O_2-Hgb dissociation curve

as pH of bl decreases (becomes more acidic), the amount of O_2 bound to Hgb at any given PO_2 also decreases

Question 37

what causes the Bohr effect?

Answer 37

it occurs bc a decreased pH yields an increase in H^+ ions that combine with Hgb, change its shape and O_2 cannot bind