Metabolism of proteins


Metabolism of proteins


          There are 20 types of amino acids in the protein taken at the time of having meal. Among these, there are nine kinds of essential amino acids because there is no synthesis of them in the body and these are supplied only by the meal. The rest of eleven amino acids are called non-essential amino acids because these are synthesized by the cells of the body.

          In the digestive tract, dietary proteins of the meal get changed into amino acids by the digestive juice, pancreas juice and enzymes of intestinal juice. Amino acids are absorbed by the villi of small intestines and they get mingled in the blood cells present inside them and then they reach into the liver by the portal vein and from the liver they reach into the normal blood circulation and because of this reason they become available for the use of all the cells and tissues. Among these available amino acids, different kinds of body cells chose special amino acids for the growth and amendment of special type of tissue and for the synthesis of nucleotides, anti bodies, hormones or other components of nitrogen. These are used in tissue proteins and by the organs and in the synthesis of protein by the liver. At the same time, the protein of tissues gets diverted into amino acids because of breaking tissues of the body.

       When there is much protein in the meal or unessential amino acids which are not necessary for the formation of body, they undergo deamination. In the process of deamination nitrogenous amino acids get disintegrate into non nitrogenous substances.   

        Nitrogenous substances (urea, ammonia, uric, acid and keratin) contain ammonia chiefly which changes into urea. This urea is expelled out from the body with urine. In the non nitrogenous portion, carbon, hydrogen and oxygen remain present in the form of glucose and they are used in the production of energy and heat.

Regularization of protein synthesis is done by the following hormones.

          Growth hormone (GH) increases the rate of protein synthesis. Insulin supplies amino acids into the cells fast. Glucocorticoids increases the anabolism of protein because of which the quantity of amino acids gets increased in the body materials. Thyroxin increases the rate of protein synthesis in the case when carbohydrates and lipids are present in sufficient quantity and it deconstructs proteins for the use of energy in the case when other nutritive elements are not available in sufficient quantity.