Definition – Protein comes from the Greek word ‘Proteo’ means ‘to take the primary place.’ are very complex nitrogenous chemical compound. it’s made of carbon, hydrogen, oxygen, nitrogen. The presence of nitrogen distinguished protein from carbohydrates & fats. except for nitrogen, elements like sulfur, phosphorous, copper, & iron are found in some proteins. Lipid combined with protein-formed lipoprotein

egg, hen's egg, boiled egg

Structure of aminoalkanoic acid

Structure of aminoalkanoic acid

The basic units from which proteins are built are amino acids. Each organic compound contains a group (COOH) or acid group & an amino or basic group.

Proteins incorporates chains of amino acids that are linked to every other by a bond (-CO-NH-).

22 different amino acids are cosmopolitan in nature. The protein obtained from plants and animals is kind of different both in amounts present & in quality. The protein content of any food is estimated by measuring the nitrogen content of the food.

Essential organic compound – Those amino acids which can not be synthesized in sufficient amounts by the body & must be provided by the diet are called essential amino acids. There are 10 essential amino acids. Among those 9 are essential for adults with it 1 for youngsters.

Non essential aminoalkanoic acid – There are 12 non essential aminoacid.This aminoalkanoic acid is synthesized in our body from another organic compound. (total – 22 amino acids)

Essential AminoAcid Non essential organic compound

Classification of protein

Functions of protein – Protein performs three main functions 

  • Structural function
  • Regulatory function
  • Energy

Structural function

  • Protein helps us in growth & development.
  • All body substance except urine & bile are made from protein
  • Proteins are the foremost constituent of muscles, organs, the secreter, & collagen.
  • Collagen is that the main structural protein of bone, ligament, skin, etc.
  • All enzymes, some hormones are like insulin are made from proteins
  • Maintenance or wear & tear
  • It also helps to repair the dead cell.

Regulatory functions – Certain amino acids & proteins have highly specialized functions within the regulation of bodily process & protection against disease.

Hemoglobin, an iron-containing protein within the blood cells, performs a very important role by transporting oxygen to the tissue cell.

Plasma protein maintains water balance & regulates the pressure level within the blood.

All enzymes & some hormones are made of protein.


Energy – Like carbohydrate-protein too provides 4kcal/gm.

Effect of deficiency & excess

It is referred to as PCM (Protein calorie malnutrition) OR PEM (Protein-energy Malnutrition) Protein deficiency is more marked during times when protein needs are more especially among preschool children in an exceedingly developing country. Leads with only protein deficiency referred to as Kwashiorkor symptom moon face, edema, pot belly, irritated in nature, red color hair, etc. Marasmus could be a combined disease of calorie + protein deficiency. Symptoms skeleton-like features, very eagerness to require food, etc.

An excess amount of protein causes kidney & cholesterol problems.

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