Biology Biomolecules SZABMU 2024 Reconduct
PMDC Verified Question 31 of 142
Which fatty acid would have the highest melting point?
A
Oleic acid
B
Lauric acid
C
Palmitic acid
D
Stearic acid
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Stearic acid
Concept:

Melting point in lipids is strictly determined by two factors: saturation (lack of double bonds) and chain length (number of carbons).

Solution:

  • First, rule out unsaturated fats. Oleic acid has a double bond (kink), preventing tight packing, making it a liquid (oil) with a very low melting point.


  • The remaining three are fully saturated (straight chains that pack tightly into solids). For saturated fats, the longer the carbon chain, the more London dispersion forces hold them together, pushing the melting point higher.


  • Lauric acid: 12 carbons.


  • Palmitic acid: 16 carbons.


  • Stearic acid: 18 carbons.


  • Because Stearic acid has the longest, fully saturated, unkinked hydrocarbon chain, it possesses the strongest intermolecular forces and thus the highest melting point (it forms very hard, solid fats).


Why other options are incorrect:

  • Oleic acid is liquid. Lauric and Palmitic are shorter, so they melt at lower temperatures than Stearic.

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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