Question

What is the difference between polypeptides and proteins?

Answer 1

Proteins are the building block of the human body. It can act as a fuel in the body and provides energy for various human activities. Protein is essential for the building, strength and maintenance of muscles and other body parts.

Complete answer:
Both polypeptides and proteins are composed of units of amino acids linked together through peptide bonds.
So now, let’s have a brief look at the differences between the polypeptide and the protein.

POLYPEPTIDE	PROTEIN
Polypeptide is a simple structure composed of a variety of amino acids linked by the peptide bonds.	Proteins are the complex polymer structure composed of many amino acids.
In the other word we can say , polypeptides are composed of amino acids	Proteins are composed of many polypeptide chains joined together through peptide bonds.
Polypeptides are composed of both the essential amino acids and the non -essential amino acids	Proteins are composed of only naturally occurring non-essential amino acids
Polypeptides have molecular weight lower than proteins.	Proteins have molecular weight higher than polypeptides.
It only has a primary structure	It has primary, secondary, tertiary and quaternary structures.
It consists of only peptide bonds joining the amino acids.	It consists of peptide bonds, dis-sulphide bonds, and ionic interactions holding the polypeptide chains together.
They play an important role in maintaining the activities of other molecules	They themselves play an important structural role in the body like hormones and enzymes.

Note:
There are $20$ non- essential amino acids present in the human body. Non- essential amino acids are those amino acids that are present naturally in the human body or are processed in the human body through some metabolic process and need not to be taken from outside the body through foods and as supplements.