Final answer:
Cell membranes alter their fluidity in response to temperature changes by changing the proportion of unsaturated and saturated fatty acids, maintaining functionality and membrane integrity for homeostasis.
Step-by-step explanation:
In response to temperature changes, cell membranes adapt by changing state to become more solid or more fluid. This process allows them to maintain the necessary fluidity for proper cell function. At lower temperatures, cell membranes become more rigid due to the compression of lipids, making the membranes less fluid and more prone to rupturing. To counteract this, organisms may increase the proportion of unsaturated fatty acids in their membranes, as these keep the membrane more fluid. Conversely, at higher temperatures, membranes become more fluid, and organisms might adjust by increasing saturated fatty acid content to maintain integrity. The maintenance of membrane fluidity is a crucial aspect of homeostasis, ensuring the proper transit of materials through the cell membrane and overall cell viability.