Lecture 4 Notes Gas Exchange PDF

Air vs. Water Reading: 602-607, 108-109 (Fick eq.), 621-628 Lecture 4: 13 Jan. Gas Exchange If you need review: 654-677 1 1  Gas Exchange what you le...

Air vs. Water Reading: 602-607, 108-109 (Fick eq.), 621-628 Lecture 4: 13 Jan. Gas Exchange If you need review: 654-677 1 1  Gas Exchange what you learned in 2601 quick review what gas(es) are we talking about? define breathing what do animals breathe? 2 2  Dalton’s Law in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases 22.1 3 3  Dalton’s Law Partial pressure Px=FxPtot Fractional concentration of the gas Total pressure of the gas mixture 4 4  O2 in Air [Fractional] constant but diffusion depends on partial pressure Dalton’s Law: Ptot=p(N2)+p(O2)+p(CO2)… P(O2) = FO2 X Ptot atmospheric pressure (Ptot) changes with altitude why? Sea Level: PO2 = Everest: PO2 = 5 5  Breathing Water: Henry’s Law (sort of) Concentration of gas x in solution Cx=APx Partial pressure of gas x Absorption coeff: concentration at 1 atm. partial pressure p. 588 (similar to solubility) 6 6  All gases are not equal Gas Solubility in Water (similar to A) O2 0.0094 CO2 0.1782 Ar ~0.009 N2 ~0.0038 7 7  What Affects Solubility? 22.2 22.2 8 8  Breathing in Lake Huron atmospheric pressure: 750.2 mmHg air FO2? PO2? CO2? A = 58.6 µg/liter/mmHg (at 20oC) Px=FxPtot Cx=APx 9 9  Breathing in Lake Titicaca atmospheric pressure: 550 mmHg CO2? A = 58.6 µg/liter/mmHg (at 20oC) Cx=APx 10 10  Diffusion-Fick Equation Gases only exchanged by diffusion J= rate of gas exchange  P1 − P2  K = Krogh coefficient J = K   X  P = Partial pressure so P1-P2 = ? X = distance separating 1 and 2 eq. 22.4 11 11  K depends on… 1. type of gas 2. material across which gas diffuses 3. area of material over which gas diffuses D = diffusion coefficient  P1 − P2  accounts for 1 and 2 A = area J = D  A   which of these can natural selection change?  X  12 12  Why Do We Breathe? what do we do when we breathe? what will happen if we don’t breathe?  P1 − P2  J = D  A    X  23.10d 13 13  Some animals don’t “breathe”… …at least not all of the time 14 14  Breathing Water why is water bad for O2 exchange? why is water bad for breathing?  P1 − P2  J = D  A    X  15 15  Strategies for Breathing in Water 1. cheat 2. don’t use much O2 3. minimize breathing effort 16 16  Unidirectional Ventilation: Fish 23.12 17 17  Ram Ventilation 18 18  23.28 19 19 20 20  Side View End View 21 21  Fish: Unidirectional Ventilation permits countercurrent gas exchange water & blood in gills flow in opposite directions why is that important? how would you describe mammalian? 23.10 22.6 (sort of) 22 22