Final answer:
Phospholipids with saturated chains pack together more tightly, leading to a more rigid membrane, compared to those with unsaturated chains, which maintain fluidity due to the kinks in their tails.
Step-by-step explanation:
The statement that phospholipids with saturated chains pack together more tightly than those with unsaturated chains is true. Saturated fatty acids have straight tails and when they are compressed, such as by decreasing temperatures, they press closely against one another, leading to a more rigid membrane. In contrast, the kinks or bends in unsaturated fatty acid tails, due to the presence of one or more double bonds, prevent tight packing and maintain space between the phospholipid molecules. This space contributes to fluidity and is crucial for maintaining membrane integrity, especially in cold environments where more saturated membranes might become too rigid and susceptible to damage.