The influence of diffusion on energy metabolism and cellular organization in skeletal muscle

I&EC 48

Bruce R Locke, locke@eng.fsu.edu1, Santosh Dasika1, Stephen T. Kinsey, kinseys@uncw.edu2, and Kristin M. Hardy2. (1) Department of Chemical and Biomedical Engineering, Florida State University, FAMU-FSU College of Engineering, 2525 Pottsdamer St., Tallahassee, FL 32310, (2) Department of Biology and Marine Biolog, University of North Carolina at Wilmington, 601 South College Road, Wilmington, NC 28403-5915
Skeletal muscle, a vital component of animals with vertebrae, is an excellent system to analyze within the framework of multiple chemical reactions coupled with diffusion in a complex, well organized, environment. The function of skeletal muscle is directly related to the relative amounts and distribution of the space allocated for aerobic metabolic capacity (mitochondria) and contractile capacity (myofibrils and sarcoplasmic reticulum). The influence of diffusion on reaction rates increases as either the diffusion distance or rate of aerobic ATP demand increases. Since diffusion distances in animal cells can range from <1 to several hundred ƒÝm, and ATP demand varies from <0.1 to >2000 ƒÝmoles g-1 min-1, it is possible that diffusion may set an upper limit on aerobic metabolic rate, which may ultimately constrain animal function. This work focuses on consideration of both oxygen and phosphate metabolites within skeletal muscle cells using the effectiveness factor and the method of volume averaging to characterize the relationship between diffusion distance and ATP turnover rate.