gas transport and exchange

Question 1

prefix, middle, suffix table

Answer 1

slide 4

Question 2

Dalton’s law of partial pressures

Answer 2

pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture

Question 3

Fick’s law of diffusion

Answer 3

molecules diffuse from regions of high concentration to low concentration at a rate proportional to the concentration gradient (P1-P2), the exchange surface area (A) and the diffusion capacity (D) of the gas, and inversely proportional to the thickness of the exchange surface (T)

Question 4

Henry’s law of solubility

Answer 4

at a constant temperature, the amount of a given gas that dissolves in a given type and volume of liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid

Question 5

Boyle’s law of pressure

Answer 5

at a constant temperature, the volume of a gas is inversely proportional to the pressure of that gas

Question 6

Charles’ law of temperature

Answer 6

at a constant pressure, the volume of a gas is proportional to the temperature of that gas

Question 7

air at sea level (%)

Answer 7

N2 (78%), O2 (21%), other gases (1%) - O2 therapy more O2, smoke has more CO2 and CO, high altitude has same % but smaller volume

Question 8

modifying cold, dry air at sea level (high PO2)

Answer 8

warmed, humidified, slowed and mixed (saturated), high (lower) PO2, higher PH20 in conducting airways, high (lower) PO2, high PCO2, same PH20 in respiratory airways

Question 9

solubility x pressure = 0.32mL/dL of O2

Answer 9

total O2 delivery at rest is 16mL/min so don’t rely on dissolved O2 in blood so need Hb

Question 10

Hb monomers

Answer 10

ferrous Fe2+ at centre of ring connected to protein chain; covalently bonded at proximal histamine residue; 2a and one of 2B (HbA), d (HbA2), y chain (HbF - foetal)

Question 11

conformational change at cooperative binding

Answer 11

as O2 binds, it allows easier binding of more O2 until not much greater capacity so less O2 bind

Question 12

allosteric

Answer 12

tense - 0% saturated, O2 released, low affinity; relaxed - 100% saturated, high affinity

Question 13

methaemoglobin (MetHb)

Answer 13

Fe3+ which doesn’t bind O2; exists in dynamic eqm with Hb Fe2+ so constant changes except at high volumes or in medication

Question 14

O2 dissociation curves

Answer 14

linear would be bad as enormous variablity with amount of binding happening - too big a range in lungs, too small a range in tissues; O2 saturation curve moves right in x-axis in older age; during exercise much greater scope for tissues taking O2 out of what is arriving

Question 15

O2 dissociation curves

Answer 15

track using P50 (partial pressure at 50% HbO2 saturation); left shift: decrease T, alkalosis, hypocapnia, decrease 2,3-DPG; shift right: increase T, acidosis (Bohr effect), hypercapnia (high CO2), increase 2,3-DPG;

Question 16

O2 dissociation curves

Answer 16

upwards shift: polycythaemia - increased O2-carrying capacity; downward shift: anaemia - impaired O2-carrying capacity - 100% Hb saturated but not enough Hb so not enough O2

Question 17

CO monoxide poisoning

Answer 17

down and left shift - decreased capacity, increased affinity, increase HbCO - CO binds making O2 bind to Hb more tightly

Question 18

foetal Hb

Answer 18

greater affinity (left) than adults HbA to ‘extract’ O2 from mother’s blood in placenta

Question 19

myoglobin

Answer 19

in muscle much greater affinity (left) than adult HbA to ‘extract’ O2 from circulating blood and store it - high intentity low duration

Question 20

Hb saturation

Answer 20

75% saturated when return back to lungs

Question 21

lung tissue circulations

Answer 21

pulmonary and bronchiole

Question 22

bronchiole drainage

Answer 22

to right side of heart, some to pulmonary veins, provides haemodilution; big reduction in PO2 but not saturation (sigmoidal shape)

Question 23

CO2 transport

Answer 23

slow eqm reaction between CO2 + H20 to H2CO3 in plasma and that to H+ and HCO3-; CO2 binds to H2O in Hb catalysed by carbonic anhydrase - fast; dissociates and HCO3- out, Cl- in; CO2 binds to Hb at amine end of globin chain - forms carbaminohaemoglobin; as H+ increases, bind to Hb molecules

Question 24

change in dissolved CO2

Answer 24

less significant as not sigmoid shape; bicarbonate is transporting most of CO2

Question 25

less O2 blood

Answer 25

carbaminoHb is greater than more O2 in blood as CO2 dissociation is basically linear - Haldane effect; if 4 O2 bound, won’t bind CO2 and vice versa

Question 26

transit time

Answer 26

amount of time blood in contact with respiratory exchange surfaces - short as otherwise will equilbriate; during exercise, if cardiac output increases, blood goes through faster

Question 27

ventilation perfusion matching: ventilation

Answer 27

gravity pulls alveoli down inferiorly; higher pressure and stretched at top; greater pressure to inflate superior more as already stretched so less scope for increasing size; PPL more negative and greater transmural pressure gradient, alveoli larger and less complient so less ventilation superiorly

Question 28

ventilation perfusion matching: perfusion

Answer 28

similar - path of least resistance; greater impact of perfusion than ventilation; as blood flow denser more susceptible to effect of gravity; higher intravascular pressure at base (gravity) as more recruitment, less resistance, higher glow rate

Question 29

ventilation:perfusion ratio

Answer 29

e^x graph - tends towards 0 then curves up to infinity