Proteins of food and their importance. The concept of nitrogen balance
The peculiarities of Proteins metabolism:
1) Proteins carry out numerous functions in the body
2) They aren’t stored but there is a “crash” storage of proteins of blood plasma
3) Permanent renew of tissues, synthesis of hormones and enzymes demand permanent intake of Proteins with food
4) Fullvalue Proteins must be supplied through the diet. Fullvalue (complete) Proteins must contain all essential amino acids. There is a standard Protein which contains 31.4% of essential amino acids
Nitrogen balance is ration between nitrogen of Proteins which are absorbed and excreted. Nitrogen of food Proteins and Proteins of the body forms the pool of free amino acids (1/3 of food Proteins, 2/3 of Proteins of the body). Final products of Proteins Metabolism are excreted through urine (60%), feaces, skin and saliva. When nitrogen of food proteins is more then nitrogen of urine it is said to be about positive nitrogen balance. It is observed in childhood and pregnancy. It is also possible in some diseases, for example polycytemia, big non-malignant tumors, hypersecretion of Growth Hormone. When nitrogen of food Proteins is less then nitrogen of urine it is said to be about negative nitrogen balance. It is observed in aging, trauma, burns, cancer, starvation and other pathological processes which are accomplished by increased cleavage of proteins of the body.