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Lecture 19, 04 Nov 2003Chapter 13, Respiration, Gas Exchange, Acid-Base Balance
Vertebrate PhysiologyECOL 437
University of ArizonaFall 2003
instr: Kevin Boninet.a.: Bret Pasch
1
Vertebrate Physiology 437
1. Blood-Gas Chemistry (CH13)
2. Announcements...
2
VOTE!
Term Paper Draft due Thursday 06 Nov.
Turn in old, relevant, graded work.
On the actual most recent draft use aCODE NAME so your paper can beanonymously reviewed by one of yourpeers.
We will give you a paper to edit/review atthe end of class on Thursday
3
Name that student:
4
Jane DavisHematologyOncologyFrench
Katie CoxTall
Kim HurdAir Force ROTC
Knut Schmidt_Nielsen 1997
Gravityand BP
5
Knut Schmidt_Nielsen 1997
Exercise
OxygenConsumptionX 20
Cardiac Output 6x
6
Chapter 13 – Blood-Gas Chemistry
Oxygen and Carbon Dioxide- Air vs. Water- Epithelial Transfer- Transport and Regulation
pH regulationChloride shiftCarbonic Anhydrase
Elevation
Skip: Diving, Swimbladder, Exercise
7
Gas composition in air O CO N
% of dry air 21 0.03 78
pp at 760 mm Hg 159 0.23 594
380mmHg (at 6000m) 79.6 0.11 297
Solubility in water (ml/L) 34 1,019 17
2 2 2
8
Why is pO2 in lungs less than ‘expected’?
Effects of Temp and Solutes on O solubility2
Temp (C) Fresh Sea
0 10.29 7.97
10 8.02 6.60
20 6.57 5.31
Increase in temp
Increase [ion]decrease solubility
9
Rate of diffusion depends on molecular weight (Graham’s Law)
Air Water
O solubility >
O rate of diffusion >
Weight of medium <
Movement of medium tidal unidirectional
(amt. needed to get O )
(take in,expel)
(less energyrequired)
2
2
2
10
Gas transfer
1. Breathing (supply air or water to respiratorysurface)
2. Diffusion of O & CO across resp. epithelium
3. Bulk transport of gases by blood
4. Diffusion across capillary walls (bloodmitochondria)
2 2
11
(humans = 50-1002 m SA)
13-1
12
Respiratory pigments
• all have either Fe or Cu ions that O binds• pigment increases O content of blood• complex of proteins and metallic ions• each has characteristic color that changes w/ O
content• ability to bind to O (affinity) affects carrying
capacity of blood for O
2+ 2+2
2
98% of O transported via carriermolecules
Gas transport in blood
2
22
2
13
hemoglobin hemocyanin hemerythrin
Metal Fe Cu Fe
Distribution over 10 phyla 2 phyla 4 phyla (all verts, many inverts) (arthropods, mollusks)
Location RBCs (verts) dissolved in intracellular plasma
Color deox – maroon colorless colorless ox – red blue reddish violet
2+ 2+ 2+
14
Knut Schmidt_Nielsen 1997
Hemoglobinand otherRespiratoryPigments
15
hememolecules
hemoglobin4 heme + 4 protein chains
can carry 4 O2
16
hemoglobinFetal hemoglobin:
γ chains (not β) w/ higher affinity for O
(enhance O transfer from mother to fetus)
Affinity for CO = 200 x’s greater than for O
CO poisoning even at low partial pressures
Antarctic icefish lack pigment
low metabolic needs = low metabolism
high cardiac output, blood volume
large heart
2
2
2
17
O dissociation curve
hyperbolic
sigmoidal
• not need lots of O to get near 100%
Cooperativity
-binding of 1st O2 facilitates more binding
-oxygenation of 1st heme group increases affinity of remaining 3 for O2
2
218
Pigment w/ High P :50
• low affinity
• high rate of O transfer to tissues
Pigment w/ Low P :
P - pp of O at which pigment is 50% saturated50 2
2
50• high affinity
• high rate of O uptake2
19
Factors that reduce affinity
1. low pH (increase [H+])
2. increase in CO2
3. elevated Temp
4. organic compounds
20
1. and 2. Increase in [CO ] or [H+]
Factors that reduce affinity
• Bohr effect
CO and H bind to hemoglobin (allosteric site), which
changes conformation of molecule and
changes binding site for O
at tissues:
CO binds to hemoglobin, decreasing affinity
for O , allowing better delivery of O
• Root effect
fishes… (skip)
2
2
2
2
2 2
+
21
Bohr Effect
CO + H O H CO H + HCO2 2 2 3
+3-
Inc in Pco inc [H+] dec pH reduces affinity2
CO enters blood at tissueshemoglobin unloads O
CO leaves blood at resp. surfacehemoglobin uptake O
2
2
2
2
Carbo
nic ac
id
Bicarb
onate
22
Knut Schmidt_Nielsen 1997
Bohr shiftas afunction ofbody size
(small animals withgreater Bohr shift[more acid sensitive]so can more readilyleave oxygen attissues at given PO)
23
Factors that reduce affinity
4. organic compounds• organophosphates in erythrocytes differ among spp.
mammals: 2,3 DPG
birds: IP
fish: ATP, GTP
• bind to hemoglobin as allosteric effectors
• used to maintain O affinity under hypoxic conditions
at high altitude (low blood [O ]) increase 2,3 DPGto increase delivery of O to tissues
2
2
2
3
24
CO transport in blood2
CO + H O H CO H + HCO
CO + OH HCO
Proportions of CO , HCO depend on pH, T, ionic strength of blood
At normal pH, Temp:
80% of CO in form of bicarbonate ion HCO
5-10% dissolved in blood
10% in form of carbamino groups
(bound to amino groups of hemoglobin)
2 2 2
2
3
3
+
-
2
-
-
3-
2 3-
3
25
Haldane effect
• deox hemo has high affinity for H creating inc. [HCO ] inblood (more CO )
•recall equations on previousslide
+
3-
2
26
Bohr effect + Haldane effect
increasing [CO2 ] decreases affinity ofhemoglobin for O2 , so binds CO2 more easily
27
CO transfer at tissue• enters/leaves blood as CO (more rapid diffusion)
• passes thru RBCs
• CO produced = O released no change in pH
only inRBC, notplasma
maintaincharge balance
passiveexchange,
bidirectional
oxygenationof hemo:acidifyinterior
(release H )
deox of hemo:inc pH (bind H )
Band IIIprotein
2
2 2
+
+
2-Chloride Shift-Carbonic Anhydrase
28
CO transfer at lung
dec. in HCO inRBC: influx
facilitateddiffusion
Acidify RBC:facilitate
HCO CO2
2
3- 3
-
29
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
• excreted continually via kidneys, gills, skin
• build-up of CO build-up of H (acidify body)
• low CO low H (alkaline body)
small overall effecton pH
+-
2+
2+
30
+
pH buffers in blood:
bicarbonate – not true buffer, but CO / HCO ratio imp. to pH
excretory organs (kidneys, gills, skin)
proteins (hemoglobin), phosphates
CO + H O H CO H + HCO
Respiration and pH
• inc. lung ventilation (low body [CO ]) inc pH
respiratory alkalosis
buffer: kidney dec. pH by excreting HCO
• dec. lung ventilation (CO excretion dec.) dec. pH
respiratory acidosis
2 3-
2 2 2+
3-
2
2
3
3-
31
If CO inc in extra., diffuse into cellto form HCO and dec.intracellular pH
efflux of H , or influx of HCOleads to rise in pH
via ATPase or
coupled w/ Nainflux
23-
+3-
+
pH buffers
Muscle vs. Brain
32
Response to acid load in cell:
• H efflux + Na influx (cation-exchange)
• H passive diffusion out of cell
• HCO influx + Cl efflux (anion-exchange)
• H efflux = HCO influxHCO inside cell CO + OH (inc. pH)
CO leaves cell to form HCO + H
or both inplasma
membrane
+
+
3- -
+3-
3-
2
-2 3+
• buffering via proteins/phosphates in cell
-
Jacob-Stewartcycle p.543
33Need to REDO:
Maintaining pH balance in the body(acid production = acid excretion)
Mammals: adjust CO excretion via lungs
acid/HCO excretion via kidneys
2
3-
34
Jackson et al. 2000Apalone - softshell turtleChrysemys - painted turtle
Mg+, Ca+ (weak base carbonates)Lactic acidbone sequestrationanoxia
35
Lung Anatomy
Nonrespiratory-Trachea ->-Bronchi ->-Bronchioles ->
Respiratory-Terminalbronchioles ->-Respiratorybronchioles ->-Alveoli
-Cilia and Mucus
(13-21)
36
(13-22)
-Gas Diffusion Barriers: 37
Lung Ventilation
-Small mammals with greater pergram O2 needs and therefore greaterper gram respiratory surface area
-Dead Space (anatomic and physiological)
Swan (13-24)
38
(13-23)
LungVentilation
39
End