Protein:

It is the organic compound contain mainly carbon, oxygen, hydrogen, nitrogen and
some time phosphorus.

source google

Structure:

Protein is basically composed of 20 different types of amino acid.
Between the amino acid the peptide bond is formed.The primary structure is held together by peptide bonds that are made during the process of protein biosynthesis.
The two ends of the polypeptide chain are referred to as the carboxyl terminus and the amino terminus based on the nature of the free group on each extremity.

Amino acid:

It is the organic compound which is made up of carboxyl group [COOH], amino group [NH2],
one Hydrogen atom, and alkyle group [R] attached with same alpha carbon.There are many amino acid present in the body of living organism but only 20 different kinds of amino acid are combined to make protein.Amino acid have same structure but alkyle group make difference between them.

source google.

Types of protein:

There are two types of protein according to their structure.
1:Linear protein:
The type of protein in which all amino acids are arranged in line and look like a thread .

source google
2:Globuler protein:
The type of protein in which the amino acid are arranged in the circle or globe.
example: hemoglobin etc

Function:

It is the big source of energy in living body. and also help in digestion , transport of oxygen in body etc are the function of protein...

I hope you got information from this blog... upvote and resteem please .....