In which type of organism would a membrane rich in unsaturated fatty acids be most adaptive?

• A. Thermophilic bacteria in hot springs
• B. Cacti in arid environments
• C. Arctic fish living in extremely cold waters
• D. Desert reptiles exposed to high temperatures

Answer: (C)

Verified step by step guidance

1. Understand the role of unsaturated fatty acids in membranes: Unsaturated fatty acids have one or more double bonds in their hydrocarbon chains, which create kinks. These kinks prevent the fatty acids from packing tightly together, increasing membrane fluidity.
2. Recognize the environmental challenge: Organisms living in extremely cold environments face the risk of their cell membranes becoming too rigid due to low temperatures. Membrane fluidity is crucial for proper cellular function, including transport and signaling.
3. Connect membrane composition to adaptation: Membranes rich in unsaturated fatty acids remain more fluid at lower temperatures compared to membranes with saturated fatty acids. This adaptation helps organisms maintain functional membranes in cold environments.
4. Analyze the options: Thermophilic bacteria and desert reptiles are exposed to high temperatures, where saturated fatty acids (which pack tightly and resist melting) are more adaptive. Cacti in arid environments face water conservation challenges, not temperature extremes. Arctic fish, living in extremely cold waters, benefit from membranes rich in unsaturated fatty acids to maintain fluidity.
5. Conclude the reasoning: Arctic fish living in extremely cold waters are the organisms for which membranes rich in unsaturated fatty acids are most adaptive, as this composition helps counteract the rigidity caused by cold temperatures.