The simplest unit of protein is amino acid. Protein can be found in both plants and animals. Animal protein is referred to as First Class Protein and also plant protein is referred to as second class protein. Read Also: Solution Classification Of Protein Read Also: Forms of solution First Class Protein First class or animal is a protein that is gotten from animals and contains all the essential amino acids in their correct proportion. Examples are ; fish, pork, meat, egg, milk etc. Second Class Protein Second class protein is a type of protein gotten from plants and vegetables which lacks two or more essential amino acids. Examples are; beans and pea. Read Also: Why libraries are important Functions Or Importance Of Protein 1. They are needed for growth and body building. 2. Repairs worn-out tissues. 3. They are used in the formation of enzymes, hormones and keratin( keratin is found in the hair and nails) 4. They are nee