Tyrosine. Molecular model of the amino acid tyrosine. Its chemical formula is C9.H11.N.O3. Atoms are represented as rods and are colour- coded: carbon (blue), hydrogen (gold), oxygen (red) and nitrogen (dark blue). Amino acids are the building blocks of proteins. Serine is a non- essential amino acid. It can be synthesised by the body and does not need to be obtained from food. Tyrosine is used to synthesise proteins and has an important role in signal transduction. Signal transduction is a process where signals are relayed inside a cell, usually by proteins such as enzymes, in order for the cell to carry out a particular function.