Word: mitochondria
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Dates: during 2000-2009
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...struggling to button your pants around your ever expanding waistline, it probably doesn't occur to you to wonder whether your body fat is brown or white. But perhaps you should. Researchers have long known that brown fat, so called because it is packed with dark-hued mitochondria (the engines that feed cells with energy), actively breaks down sugar into heat and consumes a lot more energy than white fat does. In other words, brown fat burns energy instead of storing it. However, researchers also known that while brown fat is abundant in rodents and newborns, who need...
...calories beyond what we need to live. Rats, among other species, have a far greater capacity to cope with excess calories than we do because they have more of a dark-colored tissue called brown fat. Brown fat helps produce a protein that switches off little cellular units called mitochondria, which are the cells' power plants: they help turn nutrients into energy. When they're switched off, animals don't get an energy boost. Instead, the animals literally get warmer. And as their temperature rises, calories burn effortlessly. (See TIME's health and medicine covers...
...Until now, only rodents and human newborns have been known to have any significant deposits of brown fat, so called because of its abnormally high concentration of dark-colored mitochondria, the engines that sustain cell activity. The primary purpose of brown fat is to regulate body temperature: the mitochondria-packed cells are designed to burn high quantities of sugar, the body's fuel, and release that energy as heat - a mechanism that newborns, fresh from the warm confines of the womb, rely on to keep them toasty...
...people age, however, the body becomes more adept at regulating temperature, so brown-fat stores shrink and white fat starts to emerge. (From a biological perspective, brown fat is also highly inefficient, since cells don't need heat to run; rather, they use ATP, another chemical produced by mitochondria.) Adults with appreciable amounts of brown fat are usually those who have certain types of cancer or hyperthyroidism, conditions that stimulate the growth of brown fat. (Read an article about how kids who lack self-control are more likely to gain weight...
...another. Bacteria swap genes inside our bodies, evolving resistance to antibiotics in our own gut. Some 2 billion years ago, one of our single-celled ancestors took in an oxygen-consuming bacterium. That microbe became the thousands of tiny sacs found in each of our cells today, known as mitochondria, that let us breathe oxygen. When genes move this way, it's as if two branches of the tree of life are being grafted together...