Protein and Protein Structures

Proteins are polymers of amino acids linked together through peptide bonds. Most proteins fold into specific three-dimensional structures to perform their function.

Protein structure is classified into four categories: primary, secondary, tertiary, and quaternary.

The linear sequence of amino acids in the protein is its primary structure. These sequences are read in the polymer synthesis order, from the N-terminal the free amino end, to the C-terminal, the free carboxyl end.

Secondary structures form through hydrogen bonding between the oxygen from the carbonyl group of one amino acid and the hydrogen from the amide group of another. Common secondary structures include α-helices and β-pleated sheets. 

In an α-helix, hydrogen bonds form within a single polypeptide chain, giving it a coiled structure. In β-pleated sheets, hydrogen bonds form between adjacent strands, creating a sheet-like arrangement.

These and other connecting structures, such as β-turns, further interact to form the protein’s three-dimensional structure, known as the tertiary structure.

The formation of the tertiary structure occurs due to interactions between the R-groups of the amino acids.

R-groups with opposite charge