Follicle cells in your scalp assemble proteins to build new hair. This most likely involves dehydration synthesis reactions.
Dehydration synthesis forms a peptide bond between amino acids and releases a water molecule. Amino acids connected via peptide bonds form a polypeptide chain, which then chemically interact with other polypeptides in order to create a complex three-dimensional structure of the protein.
When water participates in a reaction as a product, the process is called a dehydration synthesis reaction, since atoms of H and O are removed from the molecule, which join together to form a water molecule. This occurs at the bonds between amino acids to form proteins. This also occurs when a cell gathers its proteins to create a structure in the body, an example of this occurs when the follicular cells of the scalp gather proteins to create new hair.
