The excellence of turnip mitochondrial fraction.

Several mitochondrial fractions were screened for suitability in practical experiments designed for students, with the following issues in mind: avoiding the use of animals; minimal expenditure of labour and time; high enzyme activities; accessible instruments and low-cost materials. Turnips and potato tubers were identified as the best materials from which to extract purified mitochondria according to these criteria, with high respiratory activities and integrity maintained during five consecutive days. Mitochondrial respiration was assayed for succinate, exogenous NADH, malate/pyruvate and alpha-ketoglutarate oxidations with excellent results. At the fifth day, the respiratory control was still about 3, the integrity of the outer mitochondrial membrane maintained at values higher than 80%, and the enzymes retained more than 55% of the initial activities.