Proteins (Agriculture)

PROTEINS


Protein is name given to a class of organic compounds containing nitrogen. Every protein consists of what are known as amino acids linked together. An amino acid is an organic acid containing both amino and carboxylic groups as for example amino acetic acid. The importance of proteins is seen from the fact that they are an essential constituent of all living cells. Animal life can be supported for quite long periods by proteins alone (water and a little salt are naturally needed) whereas fat and carbohydrates cannot do this.
Proteins are the body-builders among the nutrients. They are needed for growth and repair of tissues. Almost all foods contain some protein, the richest sources being meat, fish, eggs, beans, peas, and flour.
Proteins are complicated structures, each molecule containing more than 1000 atoms. All proteins contain the elements nitrogen, carbon, oxygen, and hydrogen. Sulphur and phosphorus are also found in many proteins. Examples of proteins are casein (from milk), gluten (from flour), albumen (from eggs), and hemoglobin and serum albumin (from blood).
When proteins are digested, the large molecules are first broken up in the stomach by the enzyme pepsin, which converts the proteins into peptones. These peptones then pass into the intestine where they are acted on by the enzyme trypsin to be changed to amino acid.
The body then builds this amino acid into proteins that make muscle tissue and protoplasm.
Amino acids, which are not needed to build protein can be oxidized by the body to produce heat and energy, to be used when the body’s supply of carbohydrates and fats is used up.
A test for a protein is to add concentrated nitric, acid to the food. A yellow color, which changes to orange when ammonium hydroxide is added, indicates the presence of protein material.
Protein as a group can be rapidly and readily distinguished by a number of color reactions, such as the red coagulated mass obtained with millions reagent (mercury in nitric acid).
The splitting of various proteins and the realization that they can consist of chains of various amino acids is a fascinating story, largely clarified by the pioneer work of Fischer.