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How did studies of isolated mitochondria reveal their role in fatty acid oxidation?

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Diagram showing how epinephrine binding to a beta-adrenergic receptor on a cell membrane activates a G-protein, which then stimulates adenylyl cyclase to convert ATP into cyclic AMP (cAMP), leading to physiological effects such as increased heart rate, blood vessel dilation, and glycogen breakdown. — Biochemistry In biochemistry, researchers study the chemical substances and processes that occur in living organisms and cells. In particular, various processes by which cells gain energy, such as epinephrine-stimulated cAMP synthesis, have been deduced through the study of biochemistry.

Studies of isolated mitochondria were instrumental in identifying their role in fatty acid oxidation through the use of tissue fractionation techniques. By disrupting cells and using a centrifuge at increasing speeds, researchers were able to isolate specific cellular organelles, including mitochondria, from the rest of the cellular components.1

Once isolated, these mitochondrial fractions were tested for their capacity to perform specific metabolic steps. These experiments demonstrated that mitochondria contain the necessary enzymes to catalyze the reactions of the tricarboxylic acid cycle and the oxidation of fatty acids. This process, known as β-oxidation, occurs within the mitochondrial matrix, where fatty acid–CoA thioesters are converted into acetyl-CoA fragments, ultimately leading to the production of adenosine triphosphate (ATP).12

By isolating these organelles, biochemists could bypass the permeability barriers of the whole cell, allowing them to observe and measure the specific enzymatic pathways responsible for energy production in a controlled environment.1