Question

You construct a bilayer with equal amounts of saturated and unsaturated phospholipids. After determining the degree of permeability of this membrane to glucose (there was some permeability), you increase the proportion of unsaturated phospholipids in the bilayer. What will happen to the membrane's permeability to glucose?

A. Permeability to glucose will increase
B. Permeability to glucose will decrease
C. Permeability to glucose will stay the same
D. You can't predict the outcome. You simply have to make the measurement

Answer 1

Increasing the proportion of unsaturated phospholipids in a bilayer increases membrane fluidity and, consequently, its permeability to glucose, making answer A the most likely outcome.

Step-by-step explanation:

Increasing the proportion of unsaturated phospholipids in a bilayer affects the membrane fluidity and permeability. Unsaturated fatty acids have kinks due to the presence of C=C double bonds, which prevents the phospholipid tails from packing tightly together. This increased spacing allows for greater movement of the molecules within the membrane, hence increasing its fluidity. More fluid membranes tend to be more permeable to certain substances, such as glucose. Therefore, if you increase the proportion of unsaturated phospholipids, the permeability of the membrane to glucose will likely increase (A). However, it is important to consider other factors such as the presence of transport proteins and cholesterol that can also impact permeability.