biology 2672a comparative animal physiology n.
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Biology 2672a: Comparative Animal Physiology. Gas Exchange I: Principles & breathing in water. Gas Exchange. Getting O 2 out of the external medium and into the cells Often via the circulatory system Getting CO 2 out of the cells and into the external medium.

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biology 2672a comparative animal physiology

Biology 2672a: Comparative Animal Physiology

Gas Exchange I:

Principles & breathing in water

gas exchange
Gas Exchange
  • Getting O2 out of the external medium and into the cells
    • Often via the circulatory system
  • Getting CO2 out of the cells and into the external medium

C6H12O6 + 6O2 6CO2 + 6H2O

+ 2820 kJ/mol

where is the oxygen
Where is the oxygen?

(Cold)(Sea) water: ~0.8% O2 in solution

Air: ~21% O2 as a gas

partial pressure
Partial pressure
  • Each gas in a mix (either as a gas or in solution) exerts pressure
  • Partial pressure is the amount of pressure that the gas of interest exerts
partial pressure of gas x
Partial pressure of gas x

Partial pressure

Px=FxPtot

Fractional concentration of the gas (moles or by volume)

Total pressure of the gas mixture

Eqn. 21.2

partial pressure1
Partial pressure
  • Air
    • 20.95 % O2
    • 78.09 % N2
    • 0.93 % Ar
    • 0.038 % CO2

Px=FxPtot

PO2 = 0.2095 × 101.3 kPa = 21.22 kPa

partial pressure on mt everest
Partial pressure on Mt Everest

Px=FxPtot

  • Air
    • 20.95 % O2
    • 78.09 % N2
    • 0.93 % Ar
    • 0.038 % CO2

PO2 = 0.2095

gases dissolve in liquids
Gases dissolve in liquids
  • Not the same as having air bubbles!
  • Pliquid is proportional to Pair
  • Amount of gas in solution depends on
    • Temperature
    • Salinity
    • Gas
  • Gases that have reacted chemically do not contribute to partial pressure in solution
henry s law
Henry’s Law

Concentration in solution

C=AP

Partial pressure

Absorption coefficient

(solubility)

Eqn. 21.3

diffusion of gases

P1-P2

J=K

X

Diffusion of gases

Partial pressure

Rate of net movement of the gas

Diffusion coefficient

Distance to be diffused

Eqn. 21.4

diffusion coefficient
Diffusion coefficient
  • Depends on gas, temperature, medium
  • Also depends on the permeability of any barriers, e.g. cell membranes, cuticle, epidermis

(m2/sec × 10-9)

gas transport in organisms a combination of convection and diffusion
Gas transport in organisms - a combination of convection and diffusion

Unidirectional flow (convection) in circulatory system

Tidal convection ventilates lungs

Diffusion from capillaries into tissues

Diffusion into bloodstream

breathing water
Breathing water
  • Getting rid of CO2 isn’t a problem
    • High diffusivity & absorption
  • Getting O2is
    • Low absorption in water = low PO2
how to breathe water
How to breathe water?
  • Fast ventilation
    • More water across respiratory surface = more O2 to absorb
  • Efficient absorption
    • Would predict countercurrent exchange
  • Highly vascularised system with a large surface area
ventilatory structures
Ventilatory structures
  • Gas exchange surfaces
  • Usually highly vascularised
  • Need to open to the ‘outside world’
  • Are usually actively ventilated (convective flow of medium)
ventilatory structures1
Ventilatory structures
  • Skin
  • Gills
    • Evaginations (outpocketings)
  • Lungs
    • Invaginations (inpocketings)
  • (or some combination of the above…)
cutaneous respiration
Cutaneous respiration

Fig. 22.8 (top half)

blood vessel terminology
Blood vessel terminology
  • Afferent
    • Entering the structure (Arriving)
  • Efferent
    • Leaving the structure (Exit)
gill structure in fishes
Gill structure in fishes

Primary Lamellae

Buccal Cavity

(mouth)

Blood is oxygenated while flowing through 1° lamella

Operculum

Gill Arch

Fig. 22.10b

gill structure in fishes1
Gill structure in fishes

Afferent (deoxygenated)

Efferent (oxygenated)

2° Lamellae

Fig. 22.10b&c

counter current gas exchange
Counter-current gas exchange

Fig. 22.10d

Fig 22.4b

ventilating the gills
Ventilating the gills

Buccal-opercular pumping

Ram Ventilation

Water in at mouth, pumped out of buccal cavity with positive pressure

Water pumped out of opercular cavity with positive pressure

Fig 22.11

breathing through your butt1
Breathing through your butt
  • The Fitzroy River turtle can satisfy 70% of its oxygen requirements via cloacal respiration
  • 12 h at 25 °C (normoxic water)
  • Tidal ventilation of a ‘lung’
thursday
Thursday
  • Guest Lecture: Prof Ken Storey (Carleton U) (Freezing frogs)
    • Reading on OWL
  • Tues 21 Oct: Mid-term revision lecture
  • Thurs 23 Oct: Ethics of Animal Use
    • Reading on OWL