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1 Lecture 19, 04 Nov 2003 Chapter 13, Respiration, Gas Exchange, Acid-Base Balance Vertebrate Physiology ECOL 437 University of Arizona Fall 2003 instr: Kevin Bonine t.a.: Bret Pasch 2 Vertebrate Physiology 437 VOTE! 1. Blood-Gas Chemistry (CH13) 2. Announcements... 3 Term Paper Draft due Thursday 06 Nov. Turn in old, relevant, graded work. On the actual most recent draft use a CODE NAME so your paper can be anonymously reviewed by one of your peers. We will give you a paper to edit/review at the end of class on Thursday 4 Name that student: Jane Davis Hematology Oncology French Katie Cox Tall Kim Hurd Air Force ROTC 5 Gravity and BP Knut Schmidt_Nielsen 1997 6 Cardiac Output 6x Exercise Oxygen Consumption X 20 Knut Schmidt_Nielsen 1997 7 Chapter 13 – Blood-Gas Chemistry Oxygen and Carbon Dioxide - Air vs. Water - Epithelial Transfer - Transport and Regulation pH regulation Chloride shift Carbonic Anhydrase Elevation Skip: Diving, Swimbladder, Exercise 8 Gas composition in air O2 CO2 N2 % of dry air 21 0.03 78 159 0.23 594 0.11 297 1,019 17 pp at 760 mm Hg 380mmHg (at 6000m) 79.6 Solubility in water (ml/L) 34 Why is pO2 in lungs less than ‘expected’? Effects of Temp and Solutes on O solubility 2 Temp (C) Fresh Sea 0 10.29 7.97 10 8.02 6.60 20 6.57 5.31 Increase in temp decrease solubility Increase [ion] 9 10 Rate of diffusion depends on molecular weight (Graham’s Law) Air Water O 2 solubility > O 2 rate of diffusion > Weight of medium < (amt. needed to get O2 ) Movement of medium tidal (take in, expel) unidirectional (less energy required) 11 Gas transfer 1. Breathing (supply air or water to respiratory surface) 2. Diffusion of O & CO across resp. epithelium 2 2 (humans = 50-1002 m 3. Bulk transport of gases by blood 4. Diffusion across capillary walls (blood mitochondria) SA) 12 13-1 13 Gas transport in blood Respiratory pigments all have either Fe2+or Cu2+ ions that O2 binds pigment increases O 2content of blood complex of proteins and metallic ions each has characteristic color that changes w/ O 2 content • ability to bind to O2 (affinity) affects carrying capacity of blood for O 2 • • • • 98% of O 2 transported via carrier molecules 14 hemoglobin Metal Distribution Location Color Fe2+ over 10 phyla (all verts, many inverts) RBCs (verts) deox – maroon ox – red hemocyanin Cu2+ hemerythrin Fe2+ 2 phyla 4 phyla (arthropods, mollusks) dissolved in plasma colorless blue intracellular colorless reddish violet 15 Hemoglobin and other Respiratory Pigments Knut Schmidt_Nielsen 1997 16 hemoglobin 4 heme + 4 protein chains can carry 4 O2 heme molecules hemoglobin Fetal hemoglobin: γ chains (not β) w/ higher affinity for O 2 (enhance O 2transfer from mother to fetus) Affinity for CO = 200 x’s greater than for O 2 CO poisoning even at low partial pressures Antarctic icefish lack pigment low metabolic needs = low metabolism high cardiac output, blood volume large heart 17 18 O 2 dissociation curve hyperbolic sigmoidal • not need lots of O 2 to get near 100% Cooperativity -binding of 1st O2 facilitates more binding -oxygenation of 1st heme group increases affinity of remaining 3 for O2 P - pp of O at which pigment is 50% saturated 50 2 Pigment w/ High P 50 : • low affinity • high rate of O transfer to tissues 2 Pigment w/ Low P 50 • high affinity : • high rate of O uptake 2 19 20 Factors that reduce affinity 1. low pH (increase [H+]) 2. increase in CO2 3. elevated Temp 4. organic compounds 21 Factors that reduce affinity 1. and 2. Increase in [CO 2 ] or [H+] • Bohr effect CO 2 and H + bind to hemoglobin (allosteric site), which changes conformation of molecule and changes binding site for O 2 at tissues: CO 2 binds to hemoglobin, decreasing affinity for O2 , allowing better delivery of O 2 • Root effect fishes… (skip) 22 Bohr Effect CO2 enters blood at tissues hemoglobin unloads O 2 CO2 leaves blood at resp. surface hemoglobin uptake O2 CO + H O 2 Inc in Pco 2 2 inc [H+] H CO 2 3 H+ + HCO- dec pH 3 reduces affinity 23 Bohr shift as a function of body size (small animals with greater Bohr shift [more acid sensitive] so can more readily leave oxygen at tissues at given PO) Knut Schmidt_Nielsen 1997 Factors that reduce affinity 4. organic compounds • organophosphates in erythrocytes differ among spp. mammals: 2,3 DPG birds: IP3 fish: ATP, GTP • bind to hemoglobin as allosteric effectors • used to maintain O2 affinity under hypoxic conditions at high altitude (low blood [O 2]) to increase delivery 2of O to tissues increase 2,3 DPG 24 25 CO 2 transport in blood CO 2 + H2 O H2CO3 CO2 + OH - H + + HCO3 HCO3- Proportions of CO2 , HCO 3- depend on pH, T, ionic strength of blood At normal pH, Temp: - 80% of CO 2 in form of bicarbonate ion HCO3 5-10% dissolved in blood 10% in form of carbamino groups (bound to amino groups of hemoglobin) 26 Haldane effect • deox hemo has high affinity for H creating inc. [HCO 3 ] in blood (more2 CO ) + •recall equations on previous slide 27 Bohr effect + Haldane effect increasing [CO2 ] decreases affinity of hemoglobin for O2 , so binds CO2 more easily CO 2 transfer at tissue 28 -Chloride Shift -Carbonic Anhydrase • enters/leaves blood as CO 2 (more rapid diffusion) • passes thru RBCs • CO produced = O released 2 oxygenation of hemo: acidify interior (release H +) only in RBC, not plasma 2 no change in pH Band III protein passive exchange, bidirectional maintain charge balance deox of hemo: + inc pH (bind H ) 29 CO 2 transfer at lung facilitated diffusion Acidify RBC: facilitate HCO3CO2 - dec. in HCO3 in RBC: influx Acid-Base balancing • Animal body pH: slightly alkaline (more OH - than H+) • maintain pH for stability of proteins (and function) H+production / excretion • produced: metabolism of ingested food ingest meat: acid ingest plants: base small overall effect on pH • excreted continually via kidneys, gills, skin • build-up of CO • low CO2 2 build-up of H + (acidify body) low H+ (alkaline body) 30 31 pH buffers in blood: bicarbonate – not true buffer, but CO 2/ HCO 3-ratio imp. to pH excretory organs (kidneys, gills, skin) proteins (hemoglobin), phosphates CO 2+ H2 O H2CO3 + - H + HCO 3 Respiration and pH • inc. lung ventilation (low body [CO ]) 2 respiratory alkalosis inc pH buffer: kidney dec. pH by excreting HCO 3 • dec. lung ventilation (CO excretion dec.) dec. pH 2 respiratory acidosis 32 pH buffers If CO 2 inc in extra., diffuse into cell to form HCO 3 and dec. intracellular pH efflux of H +, or influx of HCO 3leads to rise in pH via ATPase or + coupled w/ Na influx Muscle vs. Brain Need to REDO: 33 Response to acid load in cell: • H+efflux + Na influx (cation-exchange) • H+passive diffusion out of cell or both in plasma membrane • HCO 3 influx + Cl efflux (anion-exchange) • H+efflux = HCO -3 influx HCO3- inside cell CO 2+ OH - (inc. pH) Jacob-Stewart -+ H + CO leaves cell to form HCO 2 cycle p.543 3 • buffering via proteins/phosphates in cell Maintaining pH balance in the body (acid production = acid excretion) Mammals: adjust CO 2 excretion via lungs - acid/HCO 3 excretion via kidneys 34 35 Jackson et al. 2000 Apalone - softshell turtle Chrysemys - painted turtle Mg+, Ca+ (weak base carbonates) Lactic acid bone sequestration anoxia 36 Lung Anatomy Nonrespiratory -Trachea -> -Bronchi -> -Bronchioles -> Respiratory -Terminal bronchioles -> -Respiratory bronchioles -> -Alveoli -Cilia and Mucus (13-21) -Gas Diffusion Barriers: (13-22) 37 38 Lung Ventilation -Small mammals with greater per gram O2 needs and therefore greater per gram respiratory surface area -Dead Space (anatomic and physiological) Swan (13-24) 39 Lung Ventilation (13-23) End