What are amino acids?
To understand amino acids, we must first understand proteins. Proteins are a class of biological macromolecules that participate in almost all life activities and are one of the most important macromolecules in all living organisms. Our cells and even blood are full of proteins, which are both the constituent materials of living things and the participants and regulators of various life activities. The protein is composed of 20 different amino acids. It is the free combination and arrangement of these amino acids that determine the 3-dimensional spatial structure of the protein and its biological function. Amino acids are a group of organic compounds containing amino groups and carboxyl groups. Amino groups and carboxyl groups are the basic building blocks of biologically functional macromolecular proteins. Broadly speaking, it refers to organic compounds containing basic amino groups and acidic segments, while general amino acids refer to the structural units that make up proteins. All amino acids have aC and organic group R connecting basic amino group and acidic carboxyl group. Each amino acid carries a unique R group. In other words, the R group determines the difference between different amino acids.
Figure 1. Structure of general amino acids.
How does the genetic code determine the amino acid sequence of a protein?
It is the genetic code hidden in the DNA of the nucleus that determines the amino acid sequence on the protein as well as its function and structure. After a lot of data analysis and experiments, scientists have found a genetic code called a codon. Each codon corresponds to a unique amino acid, which is determined by the sequence of the same or different three bases. Through experimental determination, there are a total of 64 codons. Different codons may correspond to the same amino acid, but each codon can only correspond to one amino acid. Among them, 61 codons correspond to amino acids, and the remaining three UAG UGA and UUA are stop codons. They provide a termination signal for the translation process, and the synthetic polypeptide chain then falls off the ribosome and enters the endoplasmic reticulum and Golgi. The body performs packaging processing; and AUG serves as a start codon to signal the beginning of the translation process.
Figure 2. Genetic code
The relationship between amino acids
The various amino acids that make up proteins also have synergy, transformation, substitution, and antagonism relationships during the body's metabolism. Methionine can be converted into cystine and possibly cysteine, but the reverse reaction cannot be performed. Therefore, methionine can meet the needs of total sulfur amino acids, but the requirement of methionine itself can only be met by methionine. Cysteine and cystine can be mutually changed. Phenylalanine can meet the needs of tyrosine because it can be converted to tyrosine, but tyrosine cannot be converted to phenylalanine. Antagonism between amino acids occurs between structurally similar amino acids, because they share the same transfer system during absorption and compete with each other. The most typical amino acids with antagonistic effects are lysine and arginine. Too much leucine can decrease the absorption rate of isoleucine and increase the excretion of isoleucine in urine. In addition, arginine and glycine can eliminate the harmful effects caused by the excess of other amino acids, which may be related to their participation in the formation of uric acid.