gas transport Flashcards
gas transport: explain how respiratory gases are transported in the blood, explain key gas laws involved including Henry, Fick, Dalton, Boyle and Charles; explain how respiratory gas transport changes in exercise and at altitude
Dalton’s law of partial pressures
pressure of a gas mixture is equal to the sum of the partial pressures of gases in that mixture
Fick’s law of diffusion
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)
Henry’s law of solubility
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
Boyle’s law of pressure
at a constant temperature, the volume of a gas is inversely proportional to the pressure of that gas
Charles’ law of temperature
at a constant pressure, the volume of a gas is proportional to the temperature of that gas
significance of difference in rate of oxygen delivery dissolved in blood (not Hb) and rate of oxygen consumption in mL min-1
16 without Hb, VO2 is 250, hence Hb required
describe structure of Hb monomers
Fe2+ ions at centre of tetrapyrrole porphyrin ring connected to globin protein chain, covalently bonded at proximal histamine residue (has two Hba subunits and two of Hb beta/sigma/gamma depending on type)
how does affinity increase exponentially as oxygen binds
cooperative binding
describe cooperative binding as an example of allosteric behaviour
middle of Hb becomes binding site for 2,3-DPG (associated with metabolic activity) when 4 O2 bind (relaxed); upon binding, pushed into tense shape (tightens) to eject oxygen
describe reaction of CO2 and H2O
CO2 + H2O H2CO3 H+ + HCO3- catalysed by carbonic anhydrase in Hb
3 ways of CO2 transport in blood
dissolves in solution, as bicarbonate, bound to Hb (amine ends of globulin chain so can carry 4 O2 and 4 CO2)
describe Cl- shift and its relevance
Cl- enter erythrocytes to maintain resting membrane potential via AE1
