Respiration in Heterotrophic Unicellular Eukaryotic Organisms

TY - JOUR

T1 - Respiration in Heterotrophic Unicellular Eukaryotic Organisms

AU - Fenchel, Tom

PY - 2014

Y1 - 2014

N2 - Surface:volume quotient, mitochondrial volume fraction, and their distribution within cells were investigated and oxygen gradients within and outside cells were modelled. Cell surface increases allometrically with cell size. Mitochondrial volume fraction is invariant with cell size and constitutes about 10% and mitochondria are predominantly found close to the outer membrane. The results predict that for small and medium sized protozoa maximum respiration rates should be proportional to cell volume (scaling exponent ≈1) and access to intracellular O2 is not limiting except at very low ambient O2-tensions. Available data do not contradict this and some evidence supports this interpretation. Cell size is ultimately limited because an increasing fraction of the mitochondria becomes exposed to near anoxic conditions with increasing cell size. The fact that mitochondria cluster close to the cell surface and the allometric change in cell shape with increasing cell size alleviates the limitation of aerobic life at low ambient O2-tension and for large cell size.

AB - Surface:volume quotient, mitochondrial volume fraction, and their distribution within cells were investigated and oxygen gradients within and outside cells were modelled. Cell surface increases allometrically with cell size. Mitochondrial volume fraction is invariant with cell size and constitutes about 10% and mitochondria are predominantly found close to the outer membrane. The results predict that for small and medium sized protozoa maximum respiration rates should be proportional to cell volume (scaling exponent ≈1) and access to intracellular O2 is not limiting except at very low ambient O2-tensions. Available data do not contradict this and some evidence supports this interpretation. Cell size is ultimately limited because an increasing fraction of the mitochondria becomes exposed to near anoxic conditions with increasing cell size. The fact that mitochondria cluster close to the cell surface and the allometric change in cell shape with increasing cell size alleviates the limitation of aerobic life at low ambient O2-tension and for large cell size.

KW - Allometry

KW - Cell geometry

KW - Mitochondrial volume fraction

KW - Protozoa

KW - Respiration rates

U2 - 10.1016/j.protis.2014.05.006

DO - 10.1016/j.protis.2014.05.006

M3 - Journal article

C2 - 24995585

AN - SCOPUS:84903692281

SN - 1434-4610

VL - 165

SP - 485

EP - 492

JO - Protist

JF - Protist

IS - 4

ER -