A model for intracellular energy transport.

A model for oxygen transfer to cells from capillaries is considered in which mitochondria are either clustered at the cell periphery around capillaries or homogeneously distributed through the cytosol. The capillary Po2 required to supply cells utilizing oxygen at the same rate is much less when mitochondria cluster around capillaries. Two alternative mechanisms are considered for distributing energy from peripheral mitochondria to the rest of the cell; i.e., diffusion of ATP or creatine phosphate with enough creatine kinase to ensure equilibrium between the approximately P carriers. The latter has clear advantages and would appear to be adequate to supply a fairly large mitochondria-free cell core (e.g., 24-micrometer diameter) with very little change in ADP levels or in the free energy of ATP hydrolysis at maximum work rates. Thus, a viable alternative to the traditional Krogh model is presented which takes into account the inhomogeneity of the diffusion pathway as a result of mitochondrial clustering.