The question is:

What kind of fatty acid tails would you expect in phospholipids of thermophilic bacteria?

Correct Answer:

✓ More saturated fatty acid tails

Why? (Simple explanation):

Thermophilic bacteria live in hot environments.

• Saturated fatty acid tails are straight and pack tightly, making the membrane less fluid and more stable at high temperatures.
• Unsaturated fatty acids have kinks that make membranes more fluid, which is better for cold environments, not hot.

So, thermophilic bacteria use saturated fatty acids to keep their membranes from melting in the heat.