Would you expect a fly that lives in Antarctica to have more saturated or unsaturated phospholipids compared to a fly that lives in the desert? Which fly, desert or arctic, would have cell membranes with increased permeability to CO2?

### A fly that lives in the arctic would have more unsaturated phospholipids because cold temperatures decrease permeability, unsaturated phospholipids increased permeability and would make up for that fact. They would have equivalent permeability to CO2.

## Step1: Understanding the properties of phospholipids### Phospholipids are a major component of all cell membranes. They can exist in two forms: saturated and unsaturated. Saturated phospholipids have no double bonds between carbon atoms, while unsaturated phospholipids have one or more double bonds. The presence of double bonds in unsaturated phospholipids causes kinks or bends in their structure, which affects their ability to pack tightly together.## Step2: Relating temperature to phospholipid structure### In colder environments like the Arctic, the cell membranes become more rigid due to the decrease in temperature. This rigidity decreases the permeability of the membrane, making it harder for substances to pass through.## Step3: Role of unsaturated phospholipids in cold environments### Unsaturated phospholipids, with their double bonds and resulting kinks, cannot pack as tightly as saturated ones. This loose packing increases the fluidity and permeability of the membrane, compensating for the decreased permeability caused by the cold temperature.## Step4: Comparing permeability to CO2 in desert and arctic environments### Desert environments are typically warmer than arctic environments. The increased temperature in deserts would make the cell membranes more fluid, and thus, they would have equivalent permeability to CO2 as the arctic flies.