Question

As compared to temperature climate a poikilothermic organism living in the arctic is richer in

• A. Cholesterol
• B. Long-chain fatty acids
• C. Protein
• D. Unsaturated fatty acids

Hint:

To maintain cell membrane fluidity in freezing conditions, organisms increase the proportion of "Unsaturated Fatty Acids" (which have lower melting points). This homeoviscous adaptation is a vital survival mechanism in cold environments.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
Poikilothermic organisms (cold-blooded organisms) cannot regulate their internal body temperature and must adapt biochemically to their environment.
To survive in freezing or extremely cold conditions (like the Arctic), these organisms must maintain cell membrane fluidity and prevent their membranes from becoming rigid and non-functional.

Step 2: Detailed Explanation:
The physical state of a cell membrane depends heavily on the chemical structure of its constituent fatty acids.
Saturated Fatty Acids: These are straight, linear hydrocarbon chains that pack together tightly.
They have high melting points and become solid and rigid at low temperatures, which can disrupt membrane function in cold environments.
Unsaturated Fatty Acids (D): These contain one or more double bonds in the cis-configuration, which introduces "kinks" or bends into the hydrocarbon chains.
These kinks prevent the fatty acid chains from packing together tightly, keeping the membrane lipid bilayer in a fluid, flexible, and functional state even at freezing temperatures.
Therefore, poikilothermic organisms living in cold Arctic environments adapt by synthesizing membranes with a much higher proportion of unsaturated fatty acids compared to organisms in warmer climates.

Step 3: Final Answer:
Arctic poikilothermic organisms have a higher proportion of unsaturated fatty acids to maintain membrane fluidity, corresponding to option (D).