Structure of fumarate
Fumarate is the conjugated base of fumaric acid which has two carboxylic acid groups (it is therefore a diacid).
Its chemical formula is HOOC-CH=CH-COO-.
Function of fumarate
Fumarate is one of the molecules involved in the Krebs cycle for the formation of ATP molecules. It is produced from the conversion of succinate by succinate dehydrogenase and is then converted into malate by fumarase.
Fumarate is the conjugated base of fumaric acid (shown here). © Ben Mills, Wikimedia, public domain