Protein has a wide range of roles in the human body, as follows: First, protein constitutes the tissue structure of the human body, protein is an important component of the body’s cells, tissues and organs, such as human muscles, internal organs contain a lot of protein. Second, transport substances, many substances in the body are transported through the blood, for example, hemoglobin in the blood can transport oxygen to the whole body. Third, catalyze chemical reactions, for example, the pancreas produces trypsin, which can catalyze the breakdown of proteins in food and thus absorption. Fourth, the nutritional function, protein can be broken down to produce energy for the body to use. Five, immune function, such as antibodies are proteins, antibodies can protect the body from infection. Sixth, to maintain the acid-base balance in the body, part of the protein in the blood also plays a role in maintaining the acid-base balance. Seven, to maintain the osmotic pressure of the blood, blood proteins, especially albumin plays the largest role. Eight, the exchange of information, such as some hormones to function, must be through the cell membrane receptors, and the receptor belongs to the protein.