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Table 5 Parameter values of the CO2 transport model.

From: Physiological responses of Daphnia pulex to acid stress

Symbol Value Unit Description
L 2.38 mm Length of exchange coordinate
A ca 7.57 mm2 Exchange surface area of the inner carapace cuticle
A tr 5.34 mm2 Exchange surface area of the trunk cuticle
Δxca 0.001 mm Thickness of the inner carapace cuticle
Δxtr 0.002 mm Thickness of the trunk cuticle
0.022 mm3 s-1 Perfusion rate
0.7 mm3 s-1 Medium flow rate
ν b 0.168 mm s-1 Hemolymph flow velocity, backward direction
ν f 0.149 mm s-1 Hemolymph flow velocity, forward direction
ν m 1.8 mm s-1 Medium flow velocity
0.0071 nmol s-1 Whole-animal CO2 production rate
0.3682 nmol mm-3 kPa-1 Physical solubility of CO2 in medium and hemolymph
K 2.10 × 10-6 nmol s-1 mm-1 kPa-1 Krogh's diffusion constant for CO2 in chitin
K' 1 10-6.325 M Dissociation equilibrium constant of CO2
K' 2 10-10.47 M Dissociation equilibrium constant of
K' A 10-8.18 M Dissociation equilibrium constant of the NB buffer
K' w 10-14 M Dissociation equilibrium constant of water
k 1 0.022 s-1 Rate constant for CO2 hydration
k 2 1010 M-1 s-1 Rate constant for the protonation of
k 3 5500 M-1 s-1 Rate constant for the reaction of CO2 with OH-
k -3 1.1 × 10-4 s-1 Rate constant for: → CO2 + OH-
k 4 1010 M-1 s-1 Rate constant for the protonation of the NB buffer
μ 1   Acceleration factor for CO2/ interconversion
ρ 0.5   Fraction of entering the outer HL lacuna
φ 0.2   Fraction of CO2 excreted into the outer HL lacuna
γ H 0.797   Hydrogen activity coefficient
C A 3.6 nmol mm-3 Concentration of the NB buffer in the hemolymph
P in 0.035 kPa Inspiratory CO2 partial pressure
pHin 8.0   pH of the inspired medium
[]in 0.6 nmol mm-3 Bicarbonate concentration of the inspired medium
  1. These parameter values were used to generate the profiles in acid-base variables shown in Figure 3D. The values for K and μ refer to the uncatalyzed case in the absence of a carbonic anhydrase in the hemolymph. The catalyzed case was derived from this parameter setting by two adjustments (μ = 10000, K = 1.30 × 10-6 nmol s-1 mm-1 kPa-1). NB = non-bicarbonate.