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 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

3

Name that student:

4

Jane DavisHematology

OncologyFrench

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 8.026.60

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 energy required)

2

2

2

10

Gas transfer

1. Breathing (supply air or water to respiratory surface)

2. Diffusion of O & CO across resp. epithelium

3. Bulk transport of gases by blood

4. Diffusion across capillary walls (blood mitochondria)

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 carrier molecules

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

Hemoglobin and other Respiratory Pigments

15

heme molecules

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

2

18

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 uptake 2

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 + HCO 2 2 2 3

+3-

Inc in Pco inc [H+] dec pH reduces affinity

2

CO enters blood at tissueshemoglobin unloads O

CO leaves blood at resp. surface

hemoglobin uptake O

2

2

2

2

Carbon

ic ac

id

Bicarb

onat

e

22

Knut Schmidt_Nielsen 1997

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)

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 DPG to 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 ] in blood (more CO )

•recall equations on previous slide

+

3

-

2

26

Bohr effect + Haldane effect

increasing [CO2 ] decreases affinity of hemoglobin 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 in RBC, not plasma

maintain charge balance

passive exchange,

bidirectional

oxygenation of hemo: acidify interior

(release H )

deox of hemo: inc pH (bind H )

Band III protein

2

2 2

+

+

2

-Chloride Shift-Carbonic Anhydrase

28

CO transfer at lung

dec. in HCO in RBC: influx

facilitated diffusion

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 effect on 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 cell to form HCO and dec.

intracellular pH

efflux of H , or influx of HCO leads to rise in pH

via ATPase or

coupled w/ Na influx

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 in plasma

membrane

+

+

3- -

+3-

3-

2

-2 3+

• buffering via proteins/phosphates in cell

-

Jacob-Stewart cycle 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-Terminal bronchioles ->-Respiratory bronchioles ->-Alveoli

-Cilia and Mucus

(13-21)

36

(13-22)

-Gas Diffusion Barriers:

37

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)

38

(13-23)

Lung Ventilation

39

End