What are prostataglandins?
PGs are a group of physiologically active _____
lipid compounds called eicosanoids that have diverse hormone-like effects 
PGs are derived enzymatically from
the fatty acid arachidonic acid.
Every PG contains
20 carbon atoms, including a 5-carbon ring.
PGs are a subclass of
eicosanoids and of the prostanoid class of fatty acid derivatives.