Who can explain to me the relationship between protein, peptide and amino acid?

Peptides are compounds formed by two or more α -amino acids linked together by peptide bonds.

Not all peptides are called small peptides.

Small molecular peptides, also known as oligopeptides, or oligopeptides, with molecular weight below 1000 dalton, are functional fragments of protein structure and have important physiological functions in organisms. It is a participant or regulator in all life processes such as cell differentiation, recognition, immunity, stress, aging and molecular evolution.

The difference between small molecular peptides and protein.

(1) small molecular peptide is easy to absorb and has no antigenicity.

Protein is a kind of macromolecule with high species specificity, which is difficult to be absorbed. It must be decomposed into amino acids or small peptides by digestion to be absorbed. At present, it is considered that small peptides can be absorbed into the circulatory system in a complete form without any waste and metabolites, and can be fully utilized by the human body. In addition, the molecular weight of protein is very large, generally above 10000. The larger the molecular weight, the more antigenic determinants on the surface, and the more stable the chemical structure. It is not easy to be destroyed or rejected by the body, and it stays in the body for a long time, so it has sufficient opportunities to contact cells that produce antibodies and stimulate the body to produce immune responses. However, small peptides have low antigenicity or no antigenicity.

(2) Small molecular peptides have strong biological activity and wide range of action.

Small molecular peptides have high biological activity, and a very small amount can also play its unique physiological role. Small molecular bioactive peptides can transmit physiological information and regulate physiological functions, and maintain normal physiological activities of human body. From cells to tissues and organs, the effects of small molecular bioactive peptides can be found.

(3) The structure of small molecular peptides is easy to be modified and synthesized.

Because the structure of small molecular peptide is much simpler than that of protein, the structure of small molecular active peptide is easy to modify and the cost of artificial synthesis is low, which provides a broad prospect for the development of polypeptide drugs.

(4) Small molecular peptides will not cause overnutrition.

Excessive intake of protein will have certain side effects, because there are many decomposition products of protein in human body, among which ammonia, ketoacid and urea will have side effects on human body, which not only increases the burden on the liver, but also easily causes indigestion and affects renal function. American scientists issued a statement saying that eating too much animal protein, such as eggs, milk and meat, may also induce heart disease. Patients with gout and liver and kidney failure should limit the intake of protein. The intake of small molecular peptides will not only cause overnutrition, but also regulate the nutritional balance of human body.

The difference between small peptide and amino acid;

After protein is ingested into human body, it is mainly absorbed and utilized by small intestine in the form of amino acids and small peptides after decomposition. The main differences between small molecular peptides and amino acids are as follows.

The absorption and metabolism rate of (1) small molecular peptides is faster than that of free amino acids, and the probability of synthesizing protein by using small molecular peptides in human body is about 25% higher than the utilization rate of amino acids.

(2) The absorption mechanisms of small peptides and amino acids are completely different. The absorption of small molecular peptides has the characteristics of fast transport speed, low energy consumption, difficult carrier saturation, non-competition and inhibition.

(3) Only 20 kinds of amino acids can be absorbed and utilized by human body. However, hundreds of small molecular peptides can be constructed by arranging and combining different kinds and quantities of amino acids. These small peptides can play a variety of biological roles.

(4) Small molecular peptides have physiological functions that amino acids can't match. They directly interfere with the metabolism of blood cells, brain and nerve cells, muscle cells, reproductive cells, endocrine cells and skin cells, and participate in regulating various physiological functions of the body.

Because of its unique advantages, small molecular peptides can supplement nutrition for some people with special physique, such as patients who are still recovering after surgery, especially after digestive tract surgery; Gastrointestinal dysfunction caused by mental stress, overwork and anorexia; Those who need to replenish nitrogen source in time and quickly after exercise; Infants with immature digestive organs or elderly people whose digestive and absorption functions begin to decline.

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