Question

Phospholipids with unsaturated fatty acyl chains ________.

1) decrease membrane fluidity
2) increase membrane fluidity
3) cause biomembranes to become thicker
4) allow hydrophilic molecules to diffuse across the lipid bilayer

Answer 1

Phospholipids with unsaturated fatty acyl chains increase membrane fluidity by introducing kinks in the hydrophobic tails, preventing tight packing and allowing more movement within the membrane. This adaptability is essential for membrane stability in different temperatures.

Step-by-step explanation:

Phospholipids with unsaturated fatty acyl chains increase membrane fluidity. This is due to the presence of double bonds in the unsaturated fatty acyl chains, which introduce kinks or bends in these chains. These kinks prevent the phospholipid molecules from packing closely together, thereby increasing the space between them. As a result, the membrane becomes more fluid because the molecules have more room to move around. Moreover, the incorporation of unsaturated fatty acids is a strategy that many organisms use to maintain membrane fluidity in colder environments.

In contrast, saturated fatty acyl chains, which do not have double bonds and therefore have straighter tails, can pack more tightly and reduce membrane fluidity. Phospholipids with saturated fatty acyl chains would make the membrane denser and more rigid, particularly in cold temperatures. However, this increased rigidity could lead to susceptibility to damage or rupturing of the membrane at low temperatures. Therefore, the presence of unsaturated fatty acyl chains is crucial for membrane stability and functionality under varying temperature conditions.