Hall, Michael Rosbash, Michael W. Hall, Michael Rosbash and Michael W. Life on Earth is adapted to the rotation of our planet. For many years we have known that living organisms, including humans, have an internal, biological clock that helps them anticipate and adapt to the discovering biological psychology pdf rhythm of the day.
But how does this clock actually work? Young were able to peek inside our biological clock and elucidate its inner workings. Their discoveries explain how plants, animals and humans adapt their biological rhythm so that it is synchronized with the Earth’s revolutions. Using fruit flies as a model organism, this year’s Nobel laureates isolated a gene that controls the normal daily biological rhythm. They showed that this gene encodes a protein that accumulates in the cell during the night, and is then degraded during the day.
Subsequently, they identified additional protein components of this machinery, exposing the mechanism governing the self-sustaining clockwork inside the cell. We now recognize that biological clocks function by the same principles in cells of other multicellular organisms, including humans. With exquisite precision, our inner clock adapts our physiology to the dramatically different phases of the day. The clock regulates critical functions such as behavior, hormone levels, sleep, body temperature and metabolism. Our wellbeing is affected when there is a temporary mismatch between our external environment and this internal biological clock, for example when we travel across several time zones and experience “jet lag”. There are also indications that chronic misalignment between our lifestyle and the rhythm dictated by our inner timekeeper is associated with increased risk for various diseases. Most living organisms anticipate and adapt to daily changes in the environment.
During the 18th century, the astronomer Jean Jacques d’Ortous de Mairan studied mimosa plants, and found that the leaves opened towards the sun during daytime and closed at dusk. He wondered what would happen if the plant was placed in constant darkness. Plants seemed to have their own biological clock. Other researchers found that not only plants, but also animals and humans, have a biological clock that helps to prepare our physiology for the fluctuations of the day.
But just how our internal circadian biological clock worked remained a mystery. During the 1970’s, Seymour Benzer and his student Ronald Konopka asked whether it would be possible to identify genes that control the circadian rhythm in fruit flies. They demonstrated that mutations in an unknown gene disrupted the circadian clock of flies. But how could this gene influence the circadian rhythm?
This year’s Nobel Laureates, who were also studying fruit flies, aimed to discover how the clock actually works. Thus, PER protein levels oscillate over a 24-hour cycle, in synchrony with the circadian rhythm. The next key goal was to understand how such circadian oscillations could be generated and sustained. The figure shows the sequence of events during a 24h oscillation. This gives rise to the inhibitory feedback mechanism that underlies a circadian rhythm. The model was tantalizing, but a few pieces of the puzzle were missing. PER protein, which is produced in the cytoplasm, would have to reach the cell nucleus, where the genetic material is located.
Jeffrey Hall and Michael Rosbash had shown that PER protein builds up in the nucleus during night, but how did it get there? TIM protein that was required for a normal circadian rhythm. The molecular components of the circadian clock. A simplified illustration of the molecular components of the circadian clock. Such a regulatory feedback mechanism explained how this oscillation of cellular protein levels emerged, but questions lingered. What controlled the frequency of the oscillations?