Circadian Rhythm and Chronobiology

All photosensitive organisms have a biological clock to cope with daily and seasonal circle of the earth. Biological clocks create circadian rhythms and regulate their processing according to cycle of the world. Circadian rhythm is an autoregulatory system and commands almost every physiological, biological, and biochemical functions of the mammalians. Therefore, biological clocks operate rhythmically with a period for a day, and this phenomenon is called as circadian rhythm. The process ongoing approximately 24 h rhythm in accordance with the meaning of the word (circa (approx.) dies (1 day). The essential purpose of biological clocks (in other word the organism’s innate timing device) is the adaptation of the living organism to environment. Circadian rhythms refer to changes in the organism’s approximately 1 day’s physiological, biochemical and biological processes. In a molecular level, there are thousands of biological clocks in the human body. The main clocks in the human brain coordinate all these cellular clocks. Thus, the rhythmical phenomenon works in a harmony with the master clock and solar cycle. However, the natural factors within the body produce circadian rhythms the environment cues also affect them. The light is the main cue that affects biological rhythm. These light–dark cycles can control of the molecular structure of biological clocks. Changing the light–dark cycles leads to lengthen, shorten or completely absent of circadian rhythms. Dysfunction of circadian cycle leads to many health problems. The studies in chronobiology provide better understanding of the rhythmic metabolism and disrupted circadian rhythms. In recent years, numerous spectacular researches have been conducted in the field of chronobiology. These researches were intended to understand metabolic process of human body. However, the molecular and genetic mechanisms of circadian clocks still not clearly known. In this study, we aimed to investigate and summarize the recent progress about circadian biological research and understand how biological clocks govern the human metabolism.