Question

Which of the following fatty acids is unsaturated?

• A. Arachidonic Acid
• B. Palmitic Acid
• C. Stearic Acid
• D. Myristic Acid.

Answer 1

The correct option is A

Arachidonic Acid

Fatty acids can be classified as saturated and unsaturated fatty acids.

Saturated fatty acids are without double bonds in their carbon chains. They have higher melting points and are solids at room temperature. They have a general formula of ${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}}{\mathrm{O}}_2$

Example:- palmitic acid$\left({\mathrm{C}}_{16}{\mathrm{H}}_{32}{\mathrm{O}}_2\right)$, stearic acid$\left({\mathrm{C}}_{18}{\mathrm{H}}_{36}{\mathrm{O}}_2\right)$, Myristic acid$\left({\mathrm{C}}_{14}{\mathrm{H}}_{28}{\mathrm{O}}_2\right)$.
Animal fats are mostly saturated fats.

Unsaturated fatty acids contain one or more double bonds in their carbon chains. They have lower melting points and are liquids at room temperature. Their general formula is${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2\mathrm{x}}{\mathrm{O}}_2$(Where x is the number of the double bond in the molecule)

Example:-

• Oleic acid (with one double bond, monoene$\left({\mathrm{C}}_{18}{\mathrm{H}}_{34}{\mathrm{O}}_2\right)$
• Linoleic acid (with two double bonds, diene$\left({\mathrm{C}}_{18}{\mathrm{H}}_{32}{\mathrm{O}}_2\right)$.
• Linolenic acid (with three double bonds, triene$\left({\mathrm{C}}_{18}{\mathrm{H}}_{30}{\mathrm{O}}_2\right)$
• Arachidonic acid (with four double bonds, tetraene,$\left({\mathrm{C}}_{20}{\mathrm{H}}_{32}{\mathrm{O}}_2\right)$

Explanation of Correct Option:

Arachidonic acid (with four double bonds, tetraene), $\left({\mathrm{C}}_{20}{\mathrm{H}}_{32}{\mathrm{O}}_2\right)$follows the general formula of unsaturated fatty acid${\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}-2\mathrm{x}}{\mathrm{O}}_2$. So this is an unsaturated fatty acid.

Explanation of Incorrect Options:

Palmitic acid$\left({\mathrm{C}}_{16}{\mathrm{H}}_{32}{\mathrm{O}}_2\right)$, Stearic acid$\left({\mathrm{C}}_{18}{\mathrm{H}}_{36}{\mathrm{O}}_2\right)$, and Myristic acid$\left({\mathrm{C}}_{14}{\mathrm{H}}_{28}{\mathrm{O}}_2\right)$ follow the general formula of saturated fatty acid. so they are saturated acid.

Hence, Option (A) is correct.