Rhythmic Respiration

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Science  01 Nov 2013:
Vol. 342, Issue 6158, pp. 570-571
DOI: 10.1126/science.1246658

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Mitochondria provide an adequate supply of energy for the myriad processes that keep a cell functioning. These organelles are often thought of as machines that continuously supply energy to the cell in the form of adenosine triphosphate (ATP). However, cellular physiology is not static; rather, the internal milieu of a cell changes according to a ∼24-hour (circadian) rhythm that is regulated by a molecular clock. On page 591 of this issue, Peek et al. show that circadian rhythms in the availability of nicotinamide adenine dinucleotide (NAD÷), a coenzyme crucial for energy conversion in the cell, control oscillations in oxidative metabolism in mammalian mitochondria (1).