In cold temperatures, phospholipid bilayers with saturated fatty acid tails are more rigid, while phospholipid bilayers with unsaturated fatty acid tails maintain the fluidity and flexibility that cells require. Based on the shape of each fatty acid tail, explain why this is the case.

The phospholipid bilayer with unsaturated fatty acid has high flexibility and fluidity due to the presence of curves in the carbon chain.

The fatty acid structure of the saturated phospholipid is straight while the unsaturated fatty acid is curved at some places in the carbon chain.

In the cold temperature, when energy is low saturated phospholipids are arranged close to each other. On the other hand, the curved structures of the unsaturated fatty acid make it harder for them to come close to each other.

Therefore, the unsaturated phospholipid maintains its fluidity even in cold temperatures.

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The reason why, in cold temperatures and depending on the type of fatty acids, the phospholipid bilayer is less or more fluid is due to the different molecular interactions that occur between the tails of both types of fatty acids. the unsaturated - which determines the fluidity of the cell membrane.

Explanation:

Temperature and saturation of fatty acid tails are two factors that affect the fluidity of the phospholipid bilayer in cell membranes.

Under normal conditions, low temperatures decrease the fluidity of the phospholipid bilayer, since it decreases the kinetic energy and increases the molecular interactions, which increases the stiffness.

However, unsaturated fatty acids - those that contain double bonds in their molecules - have a configuration that allows their tails to be more separated in their arrangement in the bilayer, which avoids the increase in molecular interactions and maintains to a certain extent the membrane fluidity, despite low temperatures.

there are so many examples for that in different areas, like biology experiment carried out in our lab recently.

here's one link: