Figure 5.

Effect of duration of mitochondrial fusion on steady- state mitochondrial activity at different frequencies of fusion events. Simulations of (a) selective and (b) nonselective fusion are compared. Short (4 min) and long (120 min) fusion events were simulated. P_t = 1/50, P_m = 1/100 events per minute. For comparison, a smooth continuous line in part b marks the curve of “Long Selective Fusion” from part a of this figure. The x axis expresses the maximal frequency of fusion events permitted. In the condition of long fusion, the actual frequency of fusion events is lower, because most mitochondria are occupied. Above 10 events per min, mitochondria in the long-fusion condition spend virtually no time in solitary state. Note that long-fusion events affect mitochondrial activity if fusions are nonselective and more so in higher and physiological fusion frequencies (∼70–100 events/mitochondrion/day).