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Mysteries beyond 24 hours: How does the biological clock work in the dark?
Whenever we feel the first ray of light in the morning or the breeze in the darkness at night, a biological clock is silently operating inside our bodies. The biological clock, or circadian rhythm, is actually a biochemical oscillator that emphasizes a 24-hour cycle. This internal "alarm clock" regulates our physiology and behavior in nature's alternation of day and night. This biological clock continues to play its role whether in the morning sunlight or in the darkness of the underground.
In an environment with no external light source, such as the low-light conditions of a laboratory, the average human internal clock runs for approximately 24.2 hours.
How the biological clock works
The basic structure of the circadian clock consists of three major elements: the master biochemical oscillator, the input pathway, and the output pathway. The period of the main biochemical oscillator is about 24 hours, and its operation is affected by external signals such as ambient light and shadow. When sufficient light and dark signals enter, the biological clock will adjust to maintain its internal rhythm.
Biological clocks are not limited to light-sensitive nerve cells; in fact, they exist in every cell in our body and work in harmony. For example, the circadian clock in vertebrates is located primarily in the suprachiasmatic nucleus (SCN) of the hypothalamus, which contains approximately 20,000 neurons and directly monitors other "accessory oscillators" in the body.
The circadian clock is the core mechanism for managing biological rhythms, helping organisms predict day and night changes in the environment and adjust their biology and behavior.
Regulation of biological clock
In different organisms, we find that the circadian clock is regulated in very different ways. Taking Drosophila as an example, researchers once revealed the mechanism of its internal clock molecules and won the Nobel Prize in Physiology or Medicine in 2017. This means that the biological clock is not just a simple mechanical structure, but a highly complex system.
In addition to the influence of gene expression, the function of the circadian clock is also regulated by a variety of post-transcriptional and post-translational modifications, which have a direct impact on the physiological performance of organisms. For example, phosphorylation of proteins can regulate their location and function within cells and affect the operation of the biological clock.
The biological clock in the dark
When an organism is in a dark environment, the biological clock can still maintain its rhythm, which represents the inherent characteristics of the operation of the biological clock. Research has proven that even in the absence of light, the biological clocks of some single-cell organisms such as cyanobacteria can still maintain an accurate 24-hour cycle, which shows the flexibility and adaptability of biological clocks.
Research on cyanobacteria shows that the circadian clock does not entirely rely on the traditional transcription-translation mechanism, and that some feedback loops can operate without DNA.
Future research directions
With the advancement of science and technology, researchers have a deeper understanding of the complexity of the biological clock. For example, through systems biology methods, scientists can analyze the operating mechanism of the biological clock and reveal its connection with other physiological processes of cells. This will not only help us gain a deeper understanding of the nature of biological rhythms, but may also affect the treatment of related diseases such as sleep disorders.
Finally, in this fast-paced world, should we be more cautious about our mental and physical health to adapt to this 24-hour operation?
