Proline. Molecular model of the amino acid proline. Its chemical formula is C5.H9.N.O2. 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. Phenylalanine is a non-essential amino acid. It can be synthesised by the body and does not need to be obtained from food. Proline is one of the main components of collagen, a support tissue found in the tendons, ligaments and connective tissues of the body. Proline also promotes the formation of bone, skin and cartilage and is important for joints and tendon functioning. It is also involved in maintaining heart muscle strength, wound healing and repairing damaged tissues.