The first part of a peptide structure is amino acids. Some amino acids are essential for biological processes in the human body. The human body consumes proteins, breaks them down and obtains the amino acids necessary for life. Amino acids are used to create the proteins for cellular activity and structure. They are the building blocks and starting point for peptide synthesis.
When two amino acids are joined, it's called a peptide bond. The nitrogen and carboxylic acid ends of the amino acids are chained together to form long peptides. These bonds are planar, but they leave some flexibility in the peptide structure. This gives the peptide the ability to fold, which is the tertiary structure that forms a protein.
Primary peptide structure is the term given to the specific sequence of amino acids that form a peptide. Different primary structures determine the way a peptide folds and creates a protein. For instance, a cysteine amino acid within a peptide creates sulfide bridges. These bridges create links within the protein structure. Sulfide bonds are important in hair strand formation. Wavy, curly hair has many sulfide bonds.
Secondary structure is separated into three forms--pleated sheets, coils and globular. The way the amino acids twist and wind within a peptide determines its function and the type of protein it creates. Pleated sheets are zigzag formations that pack closely together. Coils are twists that rotate in a circle forming a helical structure. Finally, globular structures are proteins that fold in many direction and shapes.
Once a peptide has formed its primary and secondary structure, it spontaneously folds into a three-dimensional structure called a protein. The way the peptide folds determines the protein's function, so even the slightest mutation in peptide synthesis can cause disease. For instance, the disease sickle cell anemia is from a mutation in peptide formation, which creates abnormally shaped red blood cells.