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What is Protein?

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  • Last Updated : 31 Aug, 2022
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Before going to know about protein and its uses we have to know clearly about what is protein. How protein is made? How does protein help humans for their bodies? and so on. Proteins are essential in our day-to-day life for good health and benefits in growing something faster.


Proteins are very complex molecules involved in some chemical processes that are important for life. Protein is made of small units of amino acids. These proteins help in metabolism, communication, and movement in our body.

Structural Hierarchy

There are four levels in the structural hierarchy of proteins. They are

Protein Structure


Primary structure

In the primary structure of proteins, the polypeptide chain consists of a sequence of amino acids. This primary structure has a unique protein structure. The primary structure of this level contains mainly amino acids which are present anywhere in the chain. Peptide bonds are present in the primary structure of the protein. If two amino acids are there to form a chain of proteins it is called a dipeptide bond. Similarly, if three amino acids are ready to form a link it is called tripeptide.

Characteristics of peptide bond:

  • A peptide bond is rigid and planar
  • It is not able to charge but it is polar.
  • It has a partial double bond character.

Secondary structure

This secondary structure of proteins contains a folding structure polypeptide chain. This secondary structure is formed by the H-bonds. This secondary structure is formed mostly with the alpha helix and beta pleated sheets. Example: Myoglobin. There are some types of secondary structure

  • Alpha Helix
  • Beta plated sheet
  • Strand
  • Loops

Tertiary structure

The tertiary structure of proteins is in the form of a 3Dimentional structure of the monomeric and multimeric structures. Three dimension structure of a polypeptide is simply called the tertiary structure of the protein. This tertiary structure is because of the lowest energy and greatest stability state of the polypeptide chain. The tertiary structure came from folding secondary structure of the protein.

Functions of Tertiary structure:

  • It has a unique function like interacting with other molecules.

Quaternary structure

The quaternary structure of proteins is in the form of a 3Dimensional structure of macromolecules which is a combination of individual polypeptide chains. This quaternary structure is also formed from a special combination of tertiary structures. Quaternary structure is also known as oligomeric proteins. Example: Hemoglobin

Functions of quaternary structure:

  • It helps in the chromosome replication process.
  • It helps in metabolism


  • Protein helps in maintaining good shape and fit for our body.
  • Protein repairs the body’s damaged tissues.
  • Protein is used to build bones, skin, and muscles.


Classification of proteins is based on the

  • Based on the shape
  • Based on Constitution
  • Based on the Nature of molecules

Based on shape

  • Fibrous protein
  • Globular proteins

Based on the constitution

  • Simple proteins
  • Conjugated proteins

The basic unit of protein-amino acids:

Amino acids are the basic structural unit of protein. Amino acids consist of the carbon atom, a carboxyl group (COOH), and a hydrogen atom. 

Amino acids are classified as follows

Amino Acids


  • Aromatic: Tyrosine, Tryptophan, Phenylalanine. 
  • Positively charged: Lysine, Arginine, Histidine.
  • Negatively charged: Aspartate, Glutamate.
  • Nonpolar, aliphatic: Leucine, Methionine, Isoleucine.


Enzymatic protein

The function of enzymatic protein:

  • It accelerates the metabolic process in our cells.
  • It also accelerates the metabolic process in stomach digestion, liver functions, and blood clotting.

Hormonal protein

The function of hormonal protein

  • Hormonal proteins are protein-based chemicals secreted by endocrine glands.
  • By using hormonal protein each hormone affects particular cells in the body.

Structural protein

The function of structural protein

  • Structural proteins are very important for the body because they are fibrous proteins.
  • It helps in developing muscles, bones, skin, and cartilage.

Defensive protein

The function of defensive protein

  • These defensive proteins help in developing antibodies for attacking.
  • These antibodies are developed in white blood cells to attack bacteria.

Storage protein

The function of storage protein

  • Storage protein stores minerals like potassium.
  • Storage protein contains ovalbumin and casein found in milk, and egg whites.

Transport protein

The function of transport protein

  • Transport protein called calbindin which is useful for absorption of calcium from intestinal walls.
  • Transport proteins carry important materials to the cells of the body.

Receptor protein

  • It controls the substances which enter and leave the cells.

Contractile protein.

The function of contractile protein

  • It helps in regulating the strength, speed of the heart, and muscle contractions.
  • Contractile proteins cause heart complications if the heart produces severe contractions. 

Frequently Asked Questions 

Question 1: Who discovers protein? In which year protein is discovered?


Gerardus Johannes Mulder who is a Dutch scientist discovered the protein and the name were given by Swedish chemist Jons Jacob Berzelius in 1838.

Question 2: Name some food items and protein percentage.


Food itemProtein percentage





Full Chicken




Leafy vegetables


Question 3: How much protein the human body needs every day?


Protein is very important for the body of humans. On average, the human body needs approximately 0.8 grams to process its functions.

Question 4: How many groups of amino acids leads to protein?


Protein is made of a combination of some group of amino acids. If the combination of 20 amino acids gives a protein.

Question 5: What are the disorders caused by the deficiency of protein?


 Disorders caused by the deficiency of proteins are detailed below.

  1. Muscle strength is weak
  2. Weight loss
  3. Fatigue in muscle
  4. Development in the body is less

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