Building blokes of proteins are
a. steroids
b. cholesterol
c. amino acids
d. lipids

The building blocks of protein are C. AMINO ACIDS.

Amino acids are made up of a center carbon atom bound positively to a charged amino group and a negatively charged carboxyl group and a side chain.

The primary structure of a protein is the sequence of an amino acids that are attached together by a peptide bond

The secondary structure of a protein,  the polypeptide is folded through the  mechanisms of amino acids rotating around bonds folding into a helix or a pleated sheet structure and stabilized by a hydrogen bond.