Final answer:
Omega-3 fatty acids are unsaturated with a double bond at the 3rd carbon from the tail end of the molecule. They have various health benefits and are not produced by the body.
Step-by-step explanation:
An omega-3 fatty acid is unsaturated because it has a double bond at the 3rd carbon from the tail end of the molecule. Omega-3 fatty acids are classified based on the position of the first double bond relative to the methyl end of the carbon chain. They are nutritionally important because the body does not make them, and they have been found to have various health benefits like reducing the risk of heart attacks and inflammation.