Peptide is a compound formed by α - amino acids linked together by peptide bond. It is also the intermediate product of protein hydrolysis. The compound formed by dehydration and condensation of two amino acid molecules is called dipeptide. Similarly, there are tripeptide, tetrapeptide and pentapeptide. Usually, compounds formed by dehydration and condensation of three or more amino acid molecules can be called polypeptides.
Now let's look at the peptide secretion cycle
According to the amount of secreted active peptides, people's whole life can be divided into: 1
① The period of adequate secretion (youth before the age of 25) is a period in which the endocrine quantity is balanced and the immune function is strong;
② In this period, if the secretion of active peptide is insufficient or unbalanced, there will be a variety of related sub-health status and mild disease symptoms (common in people over 40 years old);
③ Secretory deficiency period (severe deficiency period) (middle-aged and old age over 50 years old) is a serious period. If the active peptide is seriously insufficient and seriously imbalanced, it may appear very prominent aging symptoms or cause various related diseases (especially in people over 50 years old);
④ The end of secretion period (aging period), this period is very short, because the "commander" active peptide, which controls the human endocrine, does not secrete or reduces the secretion, which leads to the decline of cell function, causes organ failure and loss, and finally leads to the end of life.
The polypeptide is condensed by - NH2 and - COOH of several α - amino acids, and forms long chain compounds with more than 10 peptide bonds (- CONH -) after dehydration. It includes a variety of compounds with certain physiological activity in human body, which can be extracted from animal tissues or synthesized artificially.
Protein is a kind of long chain peptide formed by various amino acids in a certain order by peptide bond, which is crosslinked and combined by various secondary bonds. Protein has a complex four-level structure. Through different degrees of hydrolysis, the structure can be broken to produce products including peptides: protein → protein → peptone → polypeptide → oligopeptide, 2-10 long chain peptides) → amino acids. This also indicates the protein synthesis pathway. Therefore, synthetic peptides can not only be used in biochemical pharmaceutical industry, but also be used to study the synthetic pathway and structure of proteins.
