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Magic chirality: Why are almost all amino acids left-handed?
Amino acids are organic compounds containing amino and carboxylic acid functional groups. There are more than 500 amino acids in nature, but only 22 α-amino acids are crucial to life, which constitute the basic unit of all proteins.These 22 amino acids show fascinating chiral characteristics, and most of them are left-handed, which has also aroused a lot of curiosity and discussion in the scientific community.
Structure and distribution of amino acids
The general formula of α-amino acid is H2NCHRCOOH, where R represents the side chain.Although many amino acids exist in nature, further studies have shown that only these 22 amino acids play an important role in protein synthesis.These amino acids occupy the second largest component in human muscles and other tissues, and water is the first largest component.The properties and interactions of amino acids affect their functional and biological effects.
The biological role of chirality and amino acids
Chirality refers to the existence of two non-overlapping mirror forms of a substance.In amino acids, the α-carbon atom is located between the amino group and the carboxyl group. For most amino acids, it is stereochemically in 3D space, where L forms and D forms exist.However, in nature, the vast majority of amino acids exist in the form of L, which also raises many questions about their evolutionary processes and biological development.
Why only levo amino acids exist?
An interesting argument is that most life forms of dextro-amino acids are not involved in the construction of proteins and may be closely related to the early Earth's environment, chemical reactions and biosynthesis processes.
According to scientific research, this phenomenon may be due to physical conditions in the early universe, such as cosmic radiation and the possible chiral selection pressure in meteorites.This results in L-amino acids being particularly superior to D-amino acids and ultimately making them a fundamental part of life.This selective asymmetric synthesis plays an important role in the origin of life.
Diverification of amino acids and their functions
Amino acids can be classified into different categories according to the properties of their side chains, including polar and non-polar amino acids, where polar amino acids can form hydrogen bonds with water to enhance solubility.Amino acids such as serine and threonine can also participate in biological processes through chemical reactions.The diversity of these amino acid composition provides possible changes in the structure and function of proteins, allowing the same protein to be adjusted according to the environment and its own needs.
Conclusion and Reflection
In the world of amino acids, the choice of left and right has triggered more thinking about the origin of life.This phenomenon not only reveals the mysteries of nature, but also provides a window for us to understand the evolution of biological molecules.So, is the chirality of this amino acid just an accidental result of life evolution?
