Classification of Protein in Nutrition

Protein in Nutrition:

Proteins are complex nitrogenous organic compounds in which amino acids are the basic units of structure. They contain the elements carbon, hydrogen, oxygen, nitrogen and with few exceptions, sulfur. Most proteins also contain phosphorous and some specified proteins contain very small amounts of iron, copper and other inorganic elements.

Classification of Protein:

Proteins may be classified in a number of ways:

Physio Chemical Properties:

It is based on physio chemical properties. It can divided into three parts:
i. Simple Proteins: When subjected to hydrolysis by acids, alkalies or enzymes yield only amino acids, alkalies or enzymes yield only amino acids or their derivatives.

ii. Conjugated Proteins: It composed of simple proteins combined with a non-protein substance. This group includes lipo-proteins, the vehicles for the transport of fats in the blood.

iii. Derived Proteins: These proteins are substances resulting from the decomposition of simple and conjugated proteins. These include re-arrangement within the molecule without breaking the peptide bond.

Physical Shape:

It can divided into two parts:
i. Fibrous Proteins: It consist of long polypeptide chains bound together in more or less parallel fashion to form a linear shape. They are generally insoluble in body fluids and give strength to tissues in which they appear.

ii. Globular Proteins: These proteins are chains of amino acids that are coiled and tightly packed together in a round or oval shape. They are generally soluble in body fluids.

Nutritional Properties:

It can divided into two parts:
i. Essential Amino Acids: These amino acids can’t be synthesized in the body at a rate sufficient to meet body needs. They are eight essential amino acids, such as histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan, and valine.

ii. Non-Essential Amino Acids: These amino acids can synthesized from an available source of nitrogen and a carbon skeleton.