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

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Vertebrate Physiology 437

1. Blood-Gas Chemistry (CH13)

2. Announcements...

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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

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Name that student:

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Jane DavisHematologyOncologyFrench

Katie CoxTall

Kim HurdAir Force ROTC

Knut Schmidt_Nielsen 1997

Gravityand BP

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Knut Schmidt_Nielsen 1997

Exercise

OxygenConsumptionX 20

Cardiac Output 6x

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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

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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

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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

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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

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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

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(humans = 50-1002 m SA)

13-1

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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

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2

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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+

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Knut Schmidt_Nielsen 1997

Hemoglobinand otherRespiratoryPigments

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hememolecules

hemoglobin4 heme + 4 protein chains

can carry 4 O2

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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

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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

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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

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Factors that reduce affinity

1. low pH (increase [H+])

2. increase in CO2

3. elevated Temp

4. organic compounds

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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

+

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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

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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)

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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

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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

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Haldane effect

• deox hemo has high affinity for H creating inc. [HCO ] inblood (more CO )

•recall equations on previousslide

+

3-

2

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Bohr effect + Haldane effect

increasing [CO2 ] decreases affinity ofhemoglobin for O2 , so binds CO2 more easily

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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

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CO transfer at lung

dec. in HCO inRBC: influx

facilitateddiffusion

Acidify RBC:facilitate

HCO CO2

2

3- 3

-

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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+

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+

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-

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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

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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-

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Jackson et al. 2000Apalone - softshell turtleChrysemys - painted turtle

Mg+, Ca+ (weak base carbonates)Lactic acidbone sequestrationanoxia

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Lung Anatomy

Nonrespiratory-Trachea ->-Bronchi ->-Bronchioles ->

Respiratory-Terminalbronchioles ->-Respiratorybronchioles ->-Alveoli

-Cilia and Mucus

(13-21)

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(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)

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(13-23)

LungVentilation

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End