Lecture 6 Notes on Gas Exchange - PDF

Lecture 6: 17 Jan. Gas Exchange CO2 exchange Regulating breathing Reading: 677-685, 620-638 If you need to review: pg. 654-677 1 1  Respiratory Pigments covered in Bio 2601…...

Lecture 6: 17 Jan. Gas Exchange CO2 exchange Regulating breathing Reading: 677-685, 620-638 If you need to review: pg. 654-677 1 1  Respiratory Pigments covered in Bio 2601…right? you’re expected to know it hematocrit? 2 2  lives at –1.9oC Antarctic Icefish no respiratory pigments how does it get enough O2? possible advantage(s) to not having pigments? any other animals that don’t “need” pigments? 23.29 sort of 3 3  Pigments & O2 Carrying Capacity 24.4 4 4  𝐻𝑏 𝐻 + 𝑂2 ՞ 𝐻𝑏 𝑂2 + 𝐻 + 5 5  𝐻𝑏 𝐻 + 𝑂2 ՞ 𝐻𝑏 𝑂2 + 𝐻 + 6 6  𝐻𝑏 𝐻 + 𝑂2 ՞ 𝐻𝑏 𝑂2 + 𝐻 + 7 7  What can change P50? 8 8  Hb at working tissues 9 9  CO2 Excretion 24.21 where is CO2 produced? diffuses freely across epithelia/membranes but… not very soluble “as is” interconvertable to HCO3- (bicarbonate) carbonic anhydrase within RBC most CO2 transported as HCO3- CO2 + H2O  H2CO3  H+ + HCO3- CA 10 10  CO2 Excretion: Working Tissues CO2 diffuses from tissue to plasma & RBC very little binds to Hb most converted to H2CO3 by CA, then to HCO3- what happens to H+? effect on Hb? name of effect? HCO3- transported to plasma band 3 (rapid anion exchange) protein, exchanges for Cl- CO2 transported as HCO3- in plasma 11 11  CO2 Excretion: Gas X Surface HCO3- can’t diffuse across membranes most re-converted to CO2 which diffuses out of lung/gill effect on equilibrium, process below? CO2 + H2O  H2CO3  H+ + HCO3- 12 12  CO2 Excretion air breathers: a bit of a challenge fairly low [CO2] in air…but remains as CO2 requires high pCO2 for diffusion to happen  P1 − P2  J = D  A    X  13 13  Blood Gases & Breathing mammal (air breather) chemoreceptors peripheral carotid, aortic bodies: detect? central medulla: detects? which is most important in regulating breathing? 14 14  What regulates breathing? in air-breathers interpret the data 15 15  Unusual Air-Breathers where might CO2 be an issue for air breathers? how do they cope? 16 16  CO2 Excretion water breathers: usually pretty easy – low [CO2] in water – what happens to excreted CO2? – consequences? CO2 + H2O  H2CO3  H+ + HCO3-  P1 − P2  J = D  A    X  17 17  What about water breathers? filled circles 18 18  Gas Exchange: Bimodal Breathers O2: mostly lungs from air CO2: mostly gills to water requires re-routing of blood video 19 19  Gas Exchange: Skin Breathers O2: lungs in air, permeable skin in water CO2: interpret the adult data 23.15 20 20  Unusual Water Breathers what nitrogenous waste do FW fish excrete? NH3: can diffuse across gill but NH4+ can’t NH3 basic (high pK’), so converted to NH4+ in most water: always a [gradient] for NH3 excretion “soda lake”: Lake Magadi, Kenya CO2 + HCO3 + CO32- = 180 mM, pH 10.5 inhibits diffusion of CO2 across gills also inhibits excretion of NH3 at pH 10.5, much NH4+ converted back to NH3, so reduced diffusion gradient for NH3 Tilapia… 21 21  Ornitihine-Urea Cycle 22 22