Serine. Molecular model of the amino acid serine. Its chemical formula is C3.H7.N.O3. Atoms are represented as balls 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. Serine plays a crucial role in the synthesis of purines and pyrimidines, some of which are the components of DNA (deoxyribonucleic acid) and RNA (ribonucleic acid). DNA and RNA contain the instructions for the structure and function of all living organisms. Serine is also a precursor to other amino acids such as glycine, cysteine and tryptophan.