Final answer:
The statement is false; nonpolar tails in lipids are flexible due to the presence of double bonds in unsaturated fatty acids which introduce kinks, increasing membrane fluidity and preventing rigidity in colder environments.
Step-by-step explanation:
The statement that the nonpolar tails in lipids are not flexible is false. Lipid molecules, specifically phospholipids, have a significant role in cell membrane structure and function. They are amphipathic molecules, containing both a polar head and nonpolar fatty acid tails. These nonpolar tails are indeed flexible because of the presence of double bonds in unsaturated fatty acids. The double bonds introduce kinks in the tail that prevent the fatty acids from packing tightly, resulting in increased fluidity of the cell membrane. Moreover, in cold environments, organisms can adapt by increasing the proportion of unsaturated fatty acids in their membranes, maintaining fluidity by preventing the membranes from becoming too rigid. This adaptation is important to avoid rupturing due to the compression of the membrane in lower temperatures.