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MBBS QUESTION #10314
Question 1
Linoleic acid and alpha-linolenic acid are termed 'essential' fatty acids because humans must obtain them from the diet, as human cells lack the enzymes needed to:
  • Elongate fatty acid carbon chains
  • Introduce double bonds beyond the delta-9 position — i.e., desaturate fatty acids at the omega-6 and omega-3 positions✔️
  • Beta-oxidize fatty acids for energy
  • Esterify fatty acids onto a glycerol backbone
Correct Answer Explanation
Human desaturase enzymes can introduce double bonds only up to the delta-9 position; the further desaturation needed to place double bonds at the omega-6 (linoleic acid) or omega-3 (alpha-linolenic acid) positions is absent in humans, making these fatty acids dietary-essential precursors for eicosanoid and membrane lipid synthesis.