structure of amino acid

What are Proteins | Protein Definition , Structure, Classification

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What are “Proteins”?

The polymers of amino acids are proteins. By peptide linkage, these amino acids are connected.

Structure of Amino acid:

(Amino acid as a building block):

The building components of proteins are amino acids. There are two functional groups in the structure of amino acids, which are listed below:

  1. Amino functional group
  2. Carboxyl functional group
amino acid structure

“Classification of amino acids”

There are twenty different types of amino acids in all, and each one is required for the synthesis of proteins.

Non-Essential Amino acids:

Only ten of the twenty amino acids can be synthesized by our body. They are also referred to as non-essential amino acids.

Essential Amino acids:

Essential amino acids are those that our body cannot produce on its own.

Formation of Peptide Bond:

  • Peptide linkage holds two amino acids together in proteins.
  • Peptide linkage is created by removing the proton (H+) from one amino acid NH2 group and the hydroxyl (OH) from the carboxyl (COOH) group of another amino acid.
  •  The following is a description of how peptide bonds form:
peptide bond formation
  • One amino functional group is on the left side and one carboxyl functional group is still present, as can be seen in the final molecule.
  • Through peptide linkages, these functional groups can interact with additional amino acids.
  • Therefore, thousands of amino acids are connected to one another by peptide bonds in this manner to form long chain polymers known as proteins.
“Sources and uses of Protein”
  1. Origins (sources) of Protein:


  • The majority of animals possess essential amino acids, which are needed by our bodies but cannot be produced by them.
  • Meat, fish, eggs, milk, and cheese all provide significant quantities of essential amino acids.


Protein is mostly obtained from plants; for example, beans and pulses are excellent providers of amino acids.

proteins sources and uses
Applications (uses) of Protein:
  • Because our muscles, nails, hair, skin, and other protein-based tissues are made up of essential amino acids, we consume them as part of a healthy diet.
  • In addition, protein is necessary for the survival of the cells and protoplasm that make up our bodies.
  • When we heated tendons and bones in water, we found a protein called gelatin, used in bakery ingredients. We need protein in our diet daily because it gives us both physical and mental strength.
  • We know that enzymes operate as catalysts in biological reactions and that the majority of the enzymes in our bodies are protein-based.
  • Antibodies, which are defence cells in our bodies that protect us from germ attacks, are also proteins in nature.
  • In conclusion, both animals and humans must consume protein to survive.


Kwashiorkor is a particular illness caused by severe protein malnutrition. These are the signs of this illness:

1. A slow rate of growth

2. Skin discoloration

3. Hair discoloration

4. Bloating

5. A bloated belly

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