Question

Which of the following are polyunsaturated fatty acids (n-6)?
(A). Linoleic
(B). \(\gamma\)- Linolenic
(C). Arachidonic
(D). Oleic
Choose the most appropriate answer from the options given below:

• A. (A), (B) and (D) only.
• B. (A), (B) and (C) only.
• C. (A), (B), (C) and (D).
• D. (B), (C) and (D) only.

Hint:

Remember the three key fatty acid families:
\textbf{n-6 Family Head:} Linoleic Acid (LA)
\textbf{n-3 Family Head:} \(\alpha\)-Linolenic Acid (ALA)
\textbf{n-9 Family Head:} Oleic Acid (OA)
Arachidonic acid and \(\gamma\)-linolenic acid are derived from linoleic acid, so they are also in the n-6 family.

Answer 1

The Correct Option is B

Step 1: Concept Overview:
Fatty acids are classified by saturation (number of double bonds) and the position of the first double bond relative to the methyl end (n- position). Polyunsaturated fatty acids (PUFAs) have multiple double bonds (two or more). An n-6 (or omega-6) fatty acid has its first double bond at the sixth carbon from the methyl end.
Step 3: Fatty Acid Analysis:
Let's examine each fatty acid in detail:
- (A) Linoleic acid (LA): Notation: 18:2(n-6). Composition: 18 carbons, 2 double bonds, first double bond at the 6th carbon. Classification: n-6 PUFA.
- (B) \(\gamma\)-Linolenic acid (GLA): Notation: 18:3(n-6). Composition: 18 carbons, 3 double bonds, first double bond at the 6th carbon. Classification: n-6 PUFA. Note: Different from \(\alpha\)-linolenic acid (ALA), which is an n-3 PUFA.
- (C) Arachidonic acid (AA): Notation: 20:4(n-6). Composition: 20 carbons, 4 double bonds, first double bond at the 6th carbon. Classification: n-6 PUFA.
- (D) Oleic acid (OA): Notation: 18:1(n-9). Composition: 18 carbons, 1 double bond. Classification: Monounsaturated fatty acid (MUFA), not a PUFA. Double bond location: n-9 position.
Conclusion: Linoleic, \(\gamma\)-Linolenic, and Arachidonic acids are n-6 PUFAs.
Step 4: Conclusion:
The n-6 polyunsaturated fatty acids are (A), (B), and (C), corresponding to option (B).