Proteins are very important in our food for growth and repair of the body. They are organic compounds which are made up of carbon, hydrogen, oxygen, and nitrogen. There are some proteins that also contain sulphur and phosphorus. Proteins are essential for the growth of children and the teenagers. They are also needed for maintenance and making good the wear and tear of body tissues in adults.
Proteins are made up of nitrogen-containing compounds called amino acids. There are more than 20 of these amino acids and they all occur in almost all proteins. Most of the proteins which are required to perform different functions in our body are prepared within the body from the unbonded amino acids.
The proteins consumed in our food are not used by our body in their original form because proteins are insoluble in water and secondly they are very complex molecules. When the food is digested in small intestine, the proteins present in the food are broken down into simpler- substances called amino acids. The amino acids are water soluble and less complex molecules. The amino acids thus formed are absorbed from the intestine into the blood. The blood carries these free amino acids to the various body cells where they are regrouped to form specific proteins such as skin, muscle, blood and bones.
Proteins are obtained from plant sources and animal sources. Some sources of plant proteins are groundnuts, beans, whole cereals such as wheat, maize, and pulses. Several sources from animal proteins are lean meat (meat without fat), fish, eggs, milk, and cheese. These are all body building foods. These proteins are particularly needed by children.
Our body requires different types of proteins such as enzyme proteins for digestion like pepsin and trypsin. Hormones proteins is used in regulating various body functions like insulin. Transport proteins are used in carrying different substances from the blood to the various tissues of the body. Contractile proteins are used for contraction of muscles like myosin and actin.
Structural proteins are used to form the structural elements of the cells and tissues of our body like collagen. Protective proteins are used for help in fighting with infection in our body. The protein requirement for a normal adult is 1 gram per kilogram in our body and weight per day. Growing children require more protein than body weight.