ASTRID & HANNS-FRIEDER MICHLER / SCIENCE PHOTO LIBRARY ASTRID & HANNS-FRIEDER MICHLER / SCIENCE PHOTO LIBRARY
Arginine crystals, polarised light micrograph. Arginine is a semi-essential amino acid. The L-form, seen here, is one of the 20 most common natural amino acids. It can be synthesised by the body and so does not need to come from the diet. However, children are unable to make sufficient quantities for normal growth, so they must obtain it from animal or plant proteins. Arginine is involved in the production of urea, the principal form in which mammals excrete nitrogenous compounds from the body, and also plays a role in wound healing and cell division.
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